diff --git a/.gitignore b/.gitignore
index 987e2a2..bfc0cf2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 composer.lock
 vendor
+.phpunit.result.cache
\ No newline at end of file
diff --git a/README.md b/README.md
index dea2461..7b5f388 100644
--- a/README.md
+++ b/README.md
@@ -12,27 +12,27 @@ composer require tobyz/json-api-server
 ```
 
 ```php
-use Tobyz\JsonApiServer\Api;
 use Tobyz\JsonApiServer\Adapter\EloquentAdapter;
-use Tobyz\JsonApiServer\Schema\Builder;
+use Tobyz\JsonApiServer\JsonApi;
+use Tobyz\JsonApiServer\Schema\Type;
 
-$api = new Api('http://example.com/api');
+$api = new JsonApi('http://example.com/api');
 
-$api->resource('articles', new EloquentAdapter(new Article), function (Builder $schema) {
-    $schema->attribute('title');
-    $schema->hasOne('author', 'people');
-    $schema->hasMany('comments');
+$api->resource('articles', new EloquentAdapter(Article::class), function (Type $type) {
+    $type->attribute('title');
+    $type->hasOne('author')->type('people');
+    $type->hasMany('comments');
 });
 
-$api->resource('people', new EloquentAdapter(new User), function (Builder $schema) {
-    $schema->attribute('firstName');
-    $schema->attribute('lastName');
-    $schema->attribute('twitter');
+$api->resource('people', new EloquentAdapter(User::class), function (Type $type) {
+    $type->attribute('firstName');
+    $type->attribute('lastName');
+    $type->attribute('twitter');
 });
 
-$api->resource('comments', new EloquentAdapter(new Comment), function (Builder $schema) {
-    $schema->attribute('body');
-    $schema->hasOne('author', 'people');
+$api->resource('comments', new EloquentAdapter(Comment::class), function (Type $type) {
+    $type->attribute('body');
+    $type->hasOne('author')->type('people');
 });
 
 /** @var Psr\Http\Message\ServerRequestInterface $request */
@@ -60,9 +60,9 @@ The schema definition is extremely powerful and lets you easily apply [permissio
 ### Handling Requests
 
 ```php
-use Tobyz\JsonApiServer\Api;
+use Tobyz\JsonApiServer\JsonApi;
 
-$api = new Api('http://example.com/api');
+$api = new JsonApi('http://example.com/api');
 
 try {
     $response = $api->handle($request);
@@ -71,26 +71,26 @@ try {
 }
 ```
 
-`Tobyz\JsonApiServer\Api` is a [PSR-15 Request Handler](https://www.php-fig.org/psr/psr-15/). Instantiate it with your API's base URL. Convert your framework's request object into a [PSR-7 Request](https://www.php-fig.org/psr/psr-7/#321-psrhttpmessageserverrequestinterface) implementation, then let the `Api` handler take it from there. Catch any exceptions and give them back to `Api` if you want a JSON:API error response.
+`Tobyz\JsonApiServer\JsonApi` is a [PSR-15 Request Handler](https://www.php-fig.org/psr/psr-15/). Instantiate it with your API's base URL. Convert your framework's request object into a [PSR-7 Request](https://www.php-fig.org/psr/psr-7/#321-psrhttpmessageserverrequestinterface) implementation, then let the `JsonApi` handler take it from there. Catch any exceptions and give them back to `JsonApi` if you want a JSON:API error response.
 
 ### Defining Resources
 
 Define your API's resources using the `resource` method. The first argument is the [resource type](https://jsonapi.org/format/#document-resource-object-identification). The second is an instance of `Tobyz\JsonApiServer\Adapter\AdapterInterface` which will allow the handler to interact with your models. The third is a closure in which you'll build the schema for your resource.
 
 ```php
-use Tobyz\JsonApiServer\Schema\Builder;
+use Tobyz\JsonApiServer\Schema\Type;
 
-$api->resource('comments', $adapter, function (Builder $schema) {
+$api->resource('comments', $adapter, function (Schema $schema) {
     // define your schema
 });
 ```
 
-We provide an `EloquentAdapter` to hook your resources up with Laravel [Eloquent](https://laravel.com/docs/5.8/eloquent) models. Set it up with an instance of the model that your resource represents. You can [implement your own adapter](https://github.com/tobyz/json-api-server/blob/master/src/Adapter/AdapterInterface.php) if you use a different ORM.
+We provide an `EloquentAdapter` to hook your resources up with Laravel [Eloquent](https://laravel.com/docs/5.8/eloquent) models. Set it up with the name of the model that your resource represents. You can [implement your own adapter](https://github.com/tobyz/json-api-server/blob/master/src/Adapter/AdapterInterface.php) if you use a different ORM.
 
 ```php
 use Tobyz\JsonApiServer\Adapter\EloquentAdapter;
 
-$adapter = new EloquentAdapter(new User);
+$adapter = new EloquentAdapter(User::class);
 ```
 
 ### Attributes
@@ -116,10 +116,10 @@ $schema->hasOne('user');
 $schema->hasMany('comments');
 ```
 
-By default the [resource type](https://jsonapi.org/format/#document-resource-object-identification) that the relationship corresponds to will be derived from the relationship name. In the example above, the `user` relationship would correspond to the `users` resource type, while `comments` would correspond to `comments`. If you'd like to use a different resource type, provide it as a second argument:
+By default the [resource type](https://jsonapi.org/format/#document-resource-object-identification) that the relationship corresponds to will be derived from the relationship name. In the example above, the `user` relationship would correspond to the `users` resource type, while `comments` would correspond to `comments`. If you'd like to use a different resource type, call the `type` method:
 
 ```php
-$schema->hasOne('author', 'people');
+$schema->hasOne('author')->type('people');
 ```
 
 Like attributes, the relationship will automatically read and write to the relation on your model with the same name. If you'd like it to correspond to a different relation, provide it as a third argument.
@@ -173,14 +173,14 @@ $schema->hasOne('user')
 
 #### Polymorphic Relationships
 
-Define polymorphic relationships on your resource using the `morphOne` and `morphMany` methods:
+Define a relationship as polymorphic using the `polymorphic` method:
 
 ```php
-$schema->morphOne('commentable');
-$schema->morphMany('taggable');
+$schema->hasOne('commentable')->polymorphic();
+$schema->hasMany('taggable')->polymorphic();
 ```
 
-Polymorphic relationships do not accept a second argument for the resource type, because it will be automatically derived from each related resource. Nested includes cannot be requested on these relationships.
+This will mean that the resource type associated with the relationship will be derived from the model of each related resource. Consequently, nested includes cannot be requested on these relationships.
 
 ### Getters
 
@@ -257,7 +257,6 @@ $schema->attribute('email')
 
 You can provide a default value for a field to be used when creating a new resource if there is no value provided by the consumer. Pass a value or a closure to the `default` method:
 
-
 ```php
 $schema->attribute('joinedAt')
     ->default(new DateTime);
@@ -299,7 +298,7 @@ $schema->hasMany('groups')
 You can easily use Laravel's [Validation](https://laravel.com/docs/5.8/validation) component for field validation with the `rules` function:
 
 ```php
-use Tobyz\JsonApi\Server\Laravel\rules;
+use Tobyz\JsonApiServer\Laravel\rules;
 
 $schema->attribute('username')
     ->validate(rules('required', 'min:3', 'max:30'));
@@ -312,7 +311,7 @@ Use the `set` method to define custom mutation logic for your field, instead of
 ```php
 $schema->attribute('firstName')
     ->set(function ($model, $value, $request) {
-        return $model->first_name = strtolower($value);
+        $model->first_name = strtolower($value);
     });
 ```
 
@@ -396,6 +395,14 @@ You can set a default sort string to be used when the consumer has not supplied
 $schema->defaultSort('-updatedAt,-createdAt');
 ```
 
+To define sortable criteria that does not correspond to an attribute, use the `sort` method:
+
+```php
+$schema->sort('relevance', function ($query, $direction, $request) {
+    $query->orderBy('relevance', $direction);
+});
+```
+
 ### Pagination
 
 By default, resource listings are automatically [paginated](https://jsonapi.org/format/#fetching-pagination) with 20 records per page. You can change this limit using the `paginate` method on the schema builder, or you can remove it by passing `null`:
@@ -434,9 +441,11 @@ $schema->meta('requestTime', function ($request) {
 
 ### Creating Resources
 
-By default, resources are not [creatable](https://jsonapi.org/format/#crud-creating) (i.e. `POST` requests will return `403 Forbidden`). You can allow them to be created using the `creatable` and `notCreatable` methods on the schema builder:
+By default, resources are not [creatable](https://jsonapi.org/format/#crud-creating) (i.e. `POST` requests will return `403 Forbidden`). You can allow them to be created using the `creatable` and `notCreatable` methods on the schema builder. Pass a closure that returns `true` if the resource should be creatable, or no value to have it always creatable.
 
 ```php
+$schema->creatable();
+
 $schema->creatable(function ($request) {
     return $request->getAttribute('isAdmin');
 });
@@ -444,7 +453,7 @@ $schema->creatable(function ($request) {
 
 #### Customizing the Model
 
-When creating a resource, an empty model is supplied by the adapter. You may wish to provide a custom model in special circumstances. You can do so using the `create` method:
+When creating a resource, an empty model is supplied by the adapter. You may wish to override this and provide a custom model in special circumstances. You can do so using the `create` method:
 
 ```php
 $schema->create(function ($request) {
@@ -457,6 +466,8 @@ $schema->create(function ($request) {
 By default, resources are not [updatable](https://jsonapi.org/format/#crud-updating) (i.e. `PATCH` requests will return `403 Forbidden`). You can allow them to be updated using the `updatable` and `notUpdatable` methods on the schema builder:
 
 ```php
+$schema->updatable();
+
 $schema->updatable(function ($request) {
     return $request->getAttribute('isAdmin');
 });
@@ -467,6 +478,8 @@ $schema->updatable(function ($request) {
 By default, resources are not [deletable](https://jsonapi.org/format/#crud-deleting) (i.e. `DELETE` requests will return `403 Forbidden`). You can allow them to be deleted using the `deletable` and `notDeletable` methods on the schema builder:
 
 ```php
+$schema->deletable();
+
 $schema->deletable(function ($request) {
     return $request->getAttribute('isAdmin');
 });
diff --git a/composer.json b/composer.json
index a66c47a..fc727f6 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,8 @@
     "autoload": {
         "psr-4": {
             "Tobyz\\JsonApiServer\\": "src/"
-        }
+        },
+        "files": ["src/functions.php"]
     },
     "autoload-dev": {
         "psr-4": {
@@ -26,7 +27,9 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.4"
+        "dms/phpunit-arraysubset-asserts": "^0.1.0",
+        "helmich/phpunit-json-assert": "^3.0",
+        "phpunit/phpunit": "^8.0"
     },
     "config": {
         "sort-packages": true
diff --git a/src/Adapter/AdapterInterface.php b/src/Adapter/AdapterInterface.php
index 97794a8..fcd5d88 100644
--- a/src/Adapter/AdapterInterface.php
+++ b/src/Adapter/AdapterInterface.php
@@ -9,47 +9,231 @@ use Tobyz\JsonApiServer\Schema\Relationship;
 
 interface AdapterInterface
 {
-    public function handles($model);
-
-    public function create();
-
+    /**
+     * Create a new query builder instance.
+     *
+     * This is used as a basis for building the queries which show a resource
+     * or list a resource index. It will be passed around through the relevant
+     * scopes, filters, and sorting methods before finally being passed into
+     * the `find` or `get` methods.
+     *
+     * @return mixed
+     */
     public function query();
 
-    public function find($query, $id);
+    /**
+     * Manipulate the query to only include resources with the given IDs.
+     *
+     * @param $query
+     * @param array $ids
+     * @return mixed
+     */
+    public function filterByIds($query, array $ids): void;
 
+    /**
+     * Manipulate the query to only include resources with a certain attribute
+     * value.
+     *
+     * @param $query
+     * @param Attribute $attribute
+     * @param $value
+     * @return mixed
+     */
+    public function filterByAttribute($query, Attribute $attribute, $value): void;
+
+    /**
+     * Manipulate the query to only include resources with any one of the given
+     * resource IDs in a has-one relationship.
+     *
+     * @param $query
+     * @param HasOne $relationship
+     * @param array $ids
+     * @return mixed
+     */
+    public function filterByHasOne($query, HasOne $relationship, array $ids): void;
+
+    /**
+     * Manipulate the query to only include resources with any one of the given
+     * resource IDs in a has-many relationship.
+     *
+     * @param $query
+     * @param HasMany $relationship
+     * @param array $ids
+     * @return mixed
+     */
+    public function filterByHasMany($query, HasMany $relationship, array $ids): void;
+
+    /**
+     * Manipulate the query to sort by the given attribute in the given direction.
+     *
+     * @param $query
+     * @param Attribute $attribute
+     * @param string $direction
+     * @return mixed
+     */
+    public function sortByAttribute($query, Attribute $attribute, string $direction): void;
+
+    /**
+     * Manipulate the query to only include a certain number of results,
+     * starting from the given offset.
+     *
+     * @param $query
+     * @param int $limit
+     * @param int $offset
+     * @return mixed
+     */
+    public function paginate($query, int $limit, int $offset): void;
+
+    /**
+     * Find a single resource by ID from the query.
+     *
+     * @param $query
+     * @param string $id
+     * @return mixed
+     */
+    public function find($query, string $id);
+
+    /**
+     * Get a list of resources from the query.
+     *
+     * @param $query
+     * @return array
+     */
     public function get($query): array;
 
+    /**
+     * Get the number of results from the query.
+     *
+     * @param $query
+     * @return int
+     */
+    public function count($query): int;
+
+    /**
+     * Determine whether or not this resource type represents the given model.
+     *
+     * This is used for polymorphic relationships, where there are one or many
+     * related models of unknown type. The first resource type with an adapter
+     * that responds positively from this method will be used.
+     *
+     * @param mixed $model
+     * @return bool
+     */
+    public function represents($model): bool;
+
+    /**
+     * Create a new model instance.
+     *
+     * @return mixed
+     */
+    public function create();
+
+    /**
+     * Get the ID from the model.
+     *
+     * @param $model
+     * @return string
+     */
     public function getId($model): string;
 
+    /**
+     * Get the value of an attribute from the model.
+     *
+     * @param $model
+     * @param Attribute $attribute
+     * @return mixed
+     */
     public function getAttribute($model, Attribute $attribute);
 
+    /**
+     * Get the model for a has-one relationship for the model.
+     *
+     * @param $model
+     * @param HasOne $relationship
+     * @return mixed|null
+     */
     public function getHasOne($model, HasOne $relationship);
 
+    /**
+     * Get the ID of the related resource for a has-one relationship.
+     *
+     * @param $model
+     * @param HasOne $relationship
+     * @return mixed|null
+     */
+    public function getHasOneId($model, HasOne $relationship): ?string;
+
+    /**
+     * Get a list of models for a has-many relationship for the model.
+     *
+     * @param $model
+     * @param HasMany $relationship
+     * @return array
+     */
     public function getHasMany($model, HasMany $relationship): array;
 
-    public function applyAttribute($model, Attribute $attribute, $value);
+    /**
+     * Apply an attribute value to the model.
+     *
+     * @param $model
+     * @param Attribute $attribute
+     * @param $value
+     * @return mixed
+     */
+    public function setAttribute($model, Attribute $attribute, $value): void;
 
-    public function applyHasOne($model, HasOne $relationship, $related);
+    /**
+     * Apply a has-one relationship value to the model.
+     *
+     * @param $model
+     * @param HasOne $relationship
+     * @param $related
+     * @return mixed
+     */
+    public function setHasOne($model, HasOne $relationship, $related): void;
 
-    public function save($model);
+    /**
+     * Save the model.
+     *
+     * @param $model
+     * @return mixed
+     */
+    public function save($model): void;
 
-    public function saveHasMany($model, HasMany $relationship, array $related);
+    /**
+     * Save a has-many relationship for the model.
+     *
+     * @param $model
+     * @param HasMany $relationship
+     * @param array $related
+     * @return mixed
+     */
+    public function saveHasMany($model, HasMany $relationship, array $related): void;
 
-    public function delete($model);
+    /**
+     * Delete the model.
+     *
+     * @param $model
+     * @return mixed
+     */
+    public function delete($model): void;
 
-    public function filterByIds($query, array $ids);
+    /**
+     * Load information about related resources onto a collection of models.
+     *
+     * @param array $models
+     * @param array $relationships
+     * @return mixed
+     */
+    public function load(array $models, array $relationships): void;
 
-    public function filterByAttribute($query, Attribute $attribute, $value);
-
-    public function filterByHasOne($query, HasOne $relationship, array $ids);
-
-    public function filterByHasMany($query, HasMany $relationship, array $ids);
-
-    public function sortByAttribute($query, Attribute $attribute, string $direction);
-
-    public function paginate($query, int $limit, int $offset);
-
-    public function load(array $models, array $relationships);
-
-    public function loadIds(array $models, Relationship $relationship);
+    /**
+     * Load information about the IDs of related resources onto a collection
+     * of models.
+     *
+     * @param array $models
+     * @param Relationship $relationship
+     * @return mixed
+     */
+    public function loadIds(array $models, Relationship $relationship): void;
 }
diff --git a/src/Adapter/EloquentAdapter.php b/src/Adapter/EloquentAdapter.php
index fc5b7f2..4abe0b4 100644
--- a/src/Adapter/EloquentAdapter.php
+++ b/src/Adapter/EloquentAdapter.php
@@ -7,6 +7,7 @@ use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Illuminate\Database\Eloquent\SoftDeletes;
+use InvalidArgumentException;
 use Tobyz\JsonApiServer\Schema\Attribute;
 use Tobyz\JsonApiServer\Schema\HasMany;
 use Tobyz\JsonApiServer\Schema\HasOne;
@@ -24,11 +25,11 @@ class EloquentAdapter implements AdapterInterface
         $this->model = is_string($model) ? new $model : $model;
 
         if (! $this->model instanceof Model) {
-            throw new \InvalidArgumentException('Model must be an instance of '.Model::class);
+            throw new InvalidArgumentException('Model must be an instance of '.Model::class);
         }
     }
 
-    public function handles($model)
+    public function represents($model): bool
     {
         return $model instanceof $this->model;
     }
@@ -43,7 +44,7 @@ class EloquentAdapter implements AdapterInterface
         return $this->model->query();
     }
 
-    public function find($query, $id)
+    public function find($query, string $id)
     {
         return $query->find($id);
     }
@@ -63,64 +64,63 @@ class EloquentAdapter implements AdapterInterface
         return $model->getKey();
     }
 
-    public function getAttribute($model, Attribute $field)
+    public function getAttribute($model, Attribute $attribute)
     {
-        return $model->{$this->getAttributeProperty($field)};
+        return $model->{$this->getAttributeProperty($attribute)};
     }
 
-    public function getHasOneId($model, HasOne $field)
+    public function getHasOneId($model, HasOne $relationship): ?string
     {
-        $relation = $model->{$this->getRelationshipProperty($field)}();
+        $relation = $this->getRelation($model, $relationship);
 
+        // If this is a belongs-to relation, we can simply return the value of
+        // the foreign key on the model.
         if ($relation instanceof BelongsTo) {
-            $related = $relation->getRelated();
-
-            $key = $model->{$relation->getForeignKeyName()};
-
-            if ($key) {
-                return $related->forceFill([$related->getKeyName() => $key]);
-            }
-
-            return null;
+            return $model->{$relation->getForeignKeyName()};
         }
 
-        return $model->{$this->getRelationshipProperty($field)};
+        $related = $this->getRelationValue($model, $relationship);
+
+        return $related ? $related->getKey() : null;
     }
 
-    public function getHasOne($model, HasOne $field)
+    public function getHasOne($model, HasOne $relationship)
     {
-        return $model->{$this->getRelationshipProperty($field)};
+        return $this->getRelationValue($model, $relationship);
     }
 
-    public function getHasMany($model, HasMany $field): array
+    public function getHasMany($model, HasMany $relationship): array
     {
-        $collection = $model->{$this->getRelationshipProperty($field)};
+        $collection = $this->getRelationValue($model, $relationship);
 
         return $collection ? $collection->all() : [];
     }
 
-    public function applyAttribute($model, Attribute $field, $value)
+    public function setAttribute($model, Attribute $attribute, $value): void
     {
-        $model->{$this->getAttributeProperty($field)} = $value;
+        $model->{$this->getAttributeProperty($attribute)} = $value;
     }
 
-    public function applyHasOne($model, HasOne $field, $related)
+    public function setHasOne($model, HasOne $relationship, $related): void
     {
-        $model->{$this->getRelationshipProperty($field)}()->associate($related);
+        $this->getRelation($model, $relationship)->associate($related);
     }
 
-    public function save($model)
+    public function save($model): void
     {
         $model->save();
     }
 
-    public function saveHasMany($model, HasMany $field, array $related)
+    public function saveHasMany($model, HasMany $relationship, array $related): void
     {
-        $model->{$this->getRelationshipProperty($field)}()->sync(Collection::make($related));
+        $this->getRelation($model, $relationship)->sync(new Collection($related));
     }
 
-    public function delete($model)
+    public function delete($model): void
     {
+        // For models that use the SoftDeletes trait, deleting the resource from
+        // the API implies permanent deletion. Non-permanent deletion should be
+        // achieved by manipulating a resource attribute.
         if (method_exists($model, 'forceDelete')) {
             $model->forceDelete();
         } else {
@@ -128,17 +128,18 @@ class EloquentAdapter implements AdapterInterface
         }
     }
 
-    public function filterByIds($query, array $ids)
+    public function filterByIds($query, array $ids): void
     {
         $key = $query->getModel()->getQualifiedKeyName();
 
         $query->whereIn($key, $ids);
     }
 
-    public function filterByAttribute($query, Attribute $field, $value)
+    public function filterByAttribute($query, Attribute $attribute, $value): void
     {
-        $property = $this->getAttributeProperty($field);
+        $property = $this->getAttributeProperty($attribute);
 
+        // TODO: extract this into non-adapter territory
         if (preg_match('/(.+)\.\.(.+)/', $value, $matches)) {
             if ($matches[1] !== '*') {
                 $query->where($property, '>=', $matches[1]);
@@ -161,19 +162,17 @@ class EloquentAdapter implements AdapterInterface
         $query->where($property, $value);
     }
 
-    public function filterByHasOne($query, HasOne $field, array $ids)
+    public function filterByHasOne($query, HasOne $relationship, array $ids): void
     {
-        $relation = $query->getModel()->{$this->getRelationshipProperty($field)}();
+        $relation = $this->getRelation($query->getModel(), $relationship);
 
-        $foreignKey = $relation->getQualifiedForeignKeyName();
-
-        $query->whereIn($foreignKey, $ids);
+        $query->whereIn($relation->getQualifiedForeignKeyName(), $ids);
     }
 
-    public function filterByHasMany($query, HasMany $field, array $ids)
+    public function filterByHasMany($query, HasMany $relationship, array $ids): void
     {
-        $property = $this->getRelationshipProperty($field);
-        $relation = $query->getModel()->{$property}();
+        $property = $this->getRelationshipProperty($relationship);
+        $relation = $this->getRelation($query->getModel(), $relationship);
         $relatedKey = $relation->getRelated()->getQualifiedKeyName();
 
         $query->whereHas($property, function ($query) use ($relatedKey, $ids) {
@@ -181,22 +180,22 @@ class EloquentAdapter implements AdapterInterface
         });
     }
 
-    public function sortByAttribute($query, Attribute $field, string $direction)
+    public function sortByAttribute($query, Attribute $field, string $direction): void
     {
         $query->orderBy($this->getAttributeProperty($field), $direction);
     }
 
-    public function paginate($query, int $limit, int $offset)
+    public function paginate($query, int $limit, int $offset): void
     {
         $query->take($limit)->skip($offset);
     }
 
-    public function load(array $models, array $trail)
+    public function load(array $models, array $relationships): void
     {
-        (new Collection($models))->loadMissing($this->relationshipTrailToPath($trail));
+        (new Collection($models))->loadMissing($this->getRelationshipPath($relationships));
     }
 
-    public function loadIds(array $models, Relationship $relationship)
+    public function loadIds(array $models, Relationship $relationship): void
     {
         if (empty($models)) {
             return;
@@ -219,20 +218,28 @@ class EloquentAdapter implements AdapterInterface
         ]);
     }
 
-    private function getAttributeProperty(Attribute $field)
+    private function getAttributeProperty(Attribute $attribute): string
     {
-        return $field->property ?: strtolower(preg_replace('/(?<!^)[A-Z]/', '_$0', $field->name));
+        return $attribute->getProperty() ?: strtolower(preg_replace('/(?<!^)[A-Z]/', '_$0', $attribute->getName()));
     }
 
-    private function getRelationshipProperty(Relationship $field)
+    private function getRelationshipProperty(Relationship $relationship): string
     {
-        return $field->property ?: $field->name;
+        return $relationship->getProperty() ?: $relationship->getName();
     }
 
-    private function relationshipTrailToPath(array $trail)
+    private function getRelationshipPath(array $trail): string
     {
-        return implode('.', array_map(function ($relationship) {
-            return $this->getRelationshipProperty($relationship);
-        }, $trail));
+        return implode('.', array_map([$this, 'getRelationshipProperty'], $trail));
+    }
+
+    private function getRelation($model, Relationship $relationship)
+    {
+        return $model->{$this->getRelationshipProperty($relationship)}();
+    }
+
+    private function getRelationValue($model, Relationship $relationship)
+    {
+        return $model->{$this->getRelationshipProperty($relationship)};
     }
 }
diff --git a/src/Api.php b/src/Api.php
deleted file mode 100644
index f67314c..0000000
--- a/src/Api.php
+++ /dev/null
@@ -1,144 +0,0 @@
-<?php
-
-namespace Tobyz\JsonApiServer;
-
-use Closure;
-use JsonApiPhp\JsonApi;
-use Psr\Http\Message\ResponseInterface as Response;
-use Psr\Http\Message\ServerRequestInterface as Request;
-use Psr\Http\Server\RequestHandlerInterface;
-use Tobyz\JsonApiServer\Exception\BadRequestException;
-use Tobyz\JsonApiServer\Exception\MethodNotAllowedException;
-use Tobyz\JsonApiServer\Exception\NotImplementedException;
-use Tobyz\JsonApiServer\Exception\ResourceNotFoundException;
-use Tobyz\JsonApiServer\Handler\Concerns\FindsResources;
-
-class Api implements RequestHandlerInterface
-{
-    use FindsResources;
-
-    protected $resources = [];
-    protected $baseUrl;
-
-    public function __construct(string $baseUrl)
-    {
-        $this->baseUrl = $baseUrl;
-    }
-
-    public function resource(string $type, $adapter, Closure $buildSchema = null): void
-    {
-        $this->resources[$type] = new ResourceType($type, $adapter, $buildSchema);
-    }
-
-    public function getResources(): array
-    {
-        return $this->resources;
-    }
-
-    public function getResource(string $type): ResourceType
-    {
-        if (! isset($this->resources[$type])) {
-            throw new ResourceNotFoundException($type);
-        }
-
-        return $this->resources[$type];
-    }
-
-    public function handle(Request $request): Response
-    {
-        $path = $this->stripBasePath(
-            $request->getUri()->getPath()
-        );
-
-        $segments = explode('/', trim($path, '/'));
-        $count = count($segments);
-
-        $resource = $this->getResource($segments[0]);
-
-        if ($count === 1) {
-            switch ($request->getMethod()) {
-                case 'GET':
-                    return $this->handleWithHandler($request, new Handler\Index($this, $resource));
-
-                case 'POST':
-                    return $this->handleWithHandler($request, new Handler\Create($this, $resource));
-
-                default:
-                    throw new MethodNotAllowedException;
-            }
-        }
-
-        $model = $this->findResource($request, $resource, $segments[1]);
-
-        if ($count === 2) {
-            switch ($request->getMethod()) {
-                case 'PATCH':
-                    return $this->handleWithHandler($request, new Handler\Update($this, $resource, $model));
-
-                case 'GET':
-                    return $this->handleWithHandler($request, new Handler\Show($this, $resource, $model));
-
-                case 'DELETE':
-                    return $this->handleWithHandler($request, new Handler\Delete($resource, $model));
-
-                default:
-                    throw new MethodNotAllowedException;
-            }
-        }
-
-        if ($count === 3) {
-            throw new NotImplementedException;
-
-            // return $this->handleRelated($request, $resource, $model, $segments[2]);
-        }
-
-        if ($count === 4 && $segments[2] === 'relationships') {
-            throw new NotImplementedException;
-
-            // return $this->handleRelationship($request, $resource, $model, $segments[3]);
-        }
-
-        throw new BadRequestException;
-    }
-
-    private function stripBasePath(string $path): string
-    {
-        $basePath = parse_url($this->baseUrl, PHP_URL_PATH);
-
-        $len = strlen($basePath);
-
-        if (substr($path, 0, $len) === $basePath) {
-            $path = substr($path, $len + 1);
-        }
-
-        return $path;
-    }
-
-    private function handleWithHandler(Request $request, RequestHandlerInterface $handler)
-    {
-        $request = $request->withAttribute('jsonApiHandler', $handler);
-
-        return $handler->handle($request);
-    }
-
-    public function error($e)
-    {
-        if (! $e instanceof ErrorProviderInterface) {
-            $e = new Exception\InternalServerErrorException;
-        }
-
-        $errors = $e->getJsonApiErrors();
-        $status = $e->getJsonApiStatus();
-
-        $data = new JsonApi\ErrorDocument(
-            ...$errors
-        );
-
-        return new JsonApiResponse($data, $status);
-    }
-
-    public function getBaseUrl(): string
-    {
-        return $this->baseUrl;
-    }
-}
diff --git a/src/Exception/BadRequestException.php b/src/Exception/BadRequestException.php
index f299232..3523e07 100644
--- a/src/Exception/BadRequestException.php
+++ b/src/Exception/BadRequestException.php
@@ -2,10 +2,11 @@
 
 namespace Tobyz\JsonApiServer\Exception;
 
+use DomainException;
 use JsonApiPhp\JsonApi\Error;
 use Tobyz\JsonApiServer\ErrorProviderInterface;
 
-class BadRequestException extends \DomainException implements ErrorProviderInterface
+class BadRequestException extends DomainException implements ErrorProviderInterface
 {
     /**
      * @var string
diff --git a/src/Exception/ForbiddenException.php b/src/Exception/ForbiddenException.php
index 0e071e6..2113190 100644
--- a/src/Exception/ForbiddenException.php
+++ b/src/Exception/ForbiddenException.php
@@ -2,10 +2,11 @@
 
 namespace Tobyz\JsonApiServer\Exception;
 
+use DomainException;
 use JsonApiPhp\JsonApi\Error;
 use Tobyz\JsonApiServer\ErrorProviderInterface;
 
-class ForbiddenException extends \DomainException implements ErrorProviderInterface
+class ForbiddenException extends DomainException implements ErrorProviderInterface
 {
     public function getJsonApiErrors(): array
     {
diff --git a/src/Exception/InternalServerErrorException.php b/src/Exception/InternalServerErrorException.php
index a87e520..3dc5fe9 100644
--- a/src/Exception/InternalServerErrorException.php
+++ b/src/Exception/InternalServerErrorException.php
@@ -3,16 +3,17 @@
 namespace Tobyz\JsonApiServer\Exception;
 
 use JsonApiPhp\JsonApi\Error;
+use RuntimeException;
 use Tobyz\JsonApiServer\ErrorProviderInterface;
 
-class InternalServerErrorException extends \RuntimeException implements ErrorProviderInterface
+class InternalServerErrorException extends RuntimeException implements ErrorProviderInterface
 {
     public function getJsonApiErrors(): array
     {
         return [
             new Error(
                 new Error\Title('Internal Server Error'),
-                new Error\Status('500')
+                new Error\Status($this->getJsonApiStatus())
             )
         ];
     }
diff --git a/src/Exception/MethodNotAllowedException.php b/src/Exception/MethodNotAllowedException.php
index 3568c45..b6b63db 100644
--- a/src/Exception/MethodNotAllowedException.php
+++ b/src/Exception/MethodNotAllowedException.php
@@ -2,18 +2,24 @@
 
 namespace Tobyz\JsonApiServer\Exception;
 
+use DomainException as DomainExceptionAlias;
 use JsonApiPhp\JsonApi\Error;
 use Tobyz\JsonApiServer\ErrorProviderInterface;
 
-class MethodNotAllowedException extends \DomainException implements ErrorProviderInterface
+class MethodNotAllowedException extends DomainExceptionAlias implements ErrorProviderInterface
 {
     public function getJsonApiErrors(): array
     {
         return [
             new Error(
                 new Error\Title('Method Not Allowed'),
-                new Error\Status('405')
+                new Error\Status($this->getJsonApiStatus())
             )
         ];
     }
+
+    public function getJsonApiStatus(): string
+    {
+        return '405';
+    }
 }
diff --git a/src/Exception/NotAcceptableException.php b/src/Exception/NotAcceptableException.php
new file mode 100644
index 0000000..0b4b875
--- /dev/null
+++ b/src/Exception/NotAcceptableException.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Tobyz\JsonApiServer\Exception;
+
+use JsonApiPhp\JsonApi\Error;
+use RuntimeException;
+use Tobyz\JsonApiServer\ErrorProviderInterface;
+
+class NotAcceptableException extends RuntimeException implements ErrorProviderInterface
+{
+    public function getJsonApiErrors(): array
+    {
+        return [
+            new Error(
+                new Error\Title('Not Acceptable'),
+                new Error\Status($this->getJsonApiStatus())
+            )
+        ];
+    }
+
+    public function getJsonApiStatus(): string
+    {
+        return '406';
+    }
+}
diff --git a/src/Exception/NotImplementedException.php b/src/Exception/NotImplementedException.php
index 2ac27e6..0af1992 100644
--- a/src/Exception/NotImplementedException.php
+++ b/src/Exception/NotImplementedException.php
@@ -2,18 +2,24 @@
 
 namespace Tobyz\JsonApiServer\Exception;
 
+use DomainException;
 use JsonApiPhp\JsonApi\Error;
 use Tobyz\JsonApiServer\ErrorProviderInterface;
 
-class NotImplementedException extends \DomainException implements ErrorProviderInterface
+class NotImplementedException extends DomainException implements ErrorProviderInterface
 {
     public function getJsonApiErrors(): array
     {
         return [
             new Error(
                 new Error\Title('Not Implemented'),
-                new Error\Status('501')
+                new Error\Status($this->getJsonApiStatus())
             )
         ];
     }
+
+    public function getJsonApiStatus(): string
+    {
+        return '501';
+    }
 }
diff --git a/src/Exception/ResourceNotFoundException.php b/src/Exception/ResourceNotFoundException.php
index ad82593..eef6d49 100644
--- a/src/Exception/ResourceNotFoundException.php
+++ b/src/Exception/ResourceNotFoundException.php
@@ -3,9 +3,10 @@
 namespace Tobyz\JsonApiServer\Exception;
 
 use JsonApiPhp\JsonApi\Error;
+use RuntimeException;
 use Tobyz\JsonApiServer\ErrorProviderInterface;
 
-class ResourceNotFoundException extends \RuntimeException implements ErrorProviderInterface
+class ResourceNotFoundException extends RuntimeException implements ErrorProviderInterface
 {
     protected $type;
     protected $id;
diff --git a/src/Exception/UnauthorizedException.php b/src/Exception/UnauthorizedException.php
index 9f27c31..a11ad89 100644
--- a/src/Exception/UnauthorizedException.php
+++ b/src/Exception/UnauthorizedException.php
@@ -2,10 +2,11 @@
 
 namespace Tobyz\JsonApiServer\Exception;
 
+use DomainException;
 use JsonApiPhp\JsonApi\Error;
 use Tobyz\JsonApiServer\ErrorProviderInterface;
 
-class UnauthorizedException extends \DomainException implements ErrorProviderInterface
+class UnauthorizedException extends DomainException implements ErrorProviderInterface
 {
     public function getJsonApiErrors(): array
     {
diff --git a/src/Exception/UnprocessableEntityException.php b/src/Exception/UnprocessableEntityException.php
index 2d3c115..6a01632 100644
--- a/src/Exception/UnprocessableEntityException.php
+++ b/src/Exception/UnprocessableEntityException.php
@@ -2,10 +2,11 @@
 
 namespace Tobyz\JsonApiServer\Exception;
 
+use DomainException;
 use JsonApiPhp\JsonApi\Error;
 use Tobyz\JsonApiServer\ErrorProviderInterface;
 
-class UnprocessableEntityException extends \DomainException implements ErrorProviderInterface
+class UnprocessableEntityException extends DomainException implements ErrorProviderInterface
 {
     private $failures;
 
@@ -19,11 +20,19 @@ class UnprocessableEntityException extends \DomainException implements ErrorProv
     public function getJsonApiErrors(): array
     {
         return array_map(function ($failure) {
-            return new Error(
+            $members = [
                 new Error\Status($this->getJsonApiStatus()),
-                new Error\SourcePointer('/data/'.$failure['field']->location.'/'.$failure['field']->name),
-                new Error\Detail($failure['message'])
-            );
+            ];
+
+            if ($field = $failure['field']) {
+                $members[] = new Error\SourcePointer('/data/'.$field->getLocation().'/'.$field->getName());
+            }
+
+            if ($failure['message']) {
+                $members[] = new Error\Detail($failure['message']);
+            }
+
+            return new Error(...$members);
         }, $this->failures);
     }
 
diff --git a/src/Exception/UnsupportedMediaTypeException.php b/src/Exception/UnsupportedMediaTypeException.php
new file mode 100644
index 0000000..46ffdf2
--- /dev/null
+++ b/src/Exception/UnsupportedMediaTypeException.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Tobyz\JsonApiServer\Exception;
+
+use JsonApiPhp\JsonApi\Error;
+use RuntimeException;
+use Tobyz\JsonApiServer\ErrorProviderInterface;
+
+class UnsupportedMediaTypeException extends RuntimeException implements ErrorProviderInterface
+{
+    public function getJsonApiErrors(): array
+    {
+        return [
+            new Error(
+                new Error\Title('Unsupported Media Type'),
+                new Error\Status($this->getJsonApiStatus())
+            )
+        ];
+    }
+
+    public function getJsonApiStatus(): string
+    {
+        return '415';
+    }
+}
diff --git a/src/Handler/Concerns/FindsResources.php b/src/Handler/Concerns/FindsResources.php
index 11f1920..a37e32a 100644
--- a/src/Handler/Concerns/FindsResources.php
+++ b/src/Handler/Concerns/FindsResources.php
@@ -5,18 +5,17 @@ namespace Tobyz\JsonApiServer\Handler\Concerns;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Tobyz\JsonApiServer\Exception\ResourceNotFoundException;
 use Tobyz\JsonApiServer\ResourceType;
+use function Tobyz\JsonApiServer\run_callbacks;
 
 trait FindsResources
 {
-    private function findResource(Request $request, ResourceType $resource, $id)
+    private function findResource(Request $request, ResourceType $resource, string $id)
     {
         $adapter = $resource->getAdapter();
 
         $query = $adapter->query();
 
-        foreach ($resource->getSchema()->scopes as $scope) {
-            $scope($request, $query, $id);
-        }
+        run_callbacks($resource->getSchema()->getScopes(), [$query, $request, $id]);
 
         $model = $adapter->find($query, $id);
 
diff --git a/src/Handler/Concerns/IncludesData.php b/src/Handler/Concerns/IncludesData.php
index 6c46b00..13b2bb3 100644
--- a/src/Handler/Concerns/IncludesData.php
+++ b/src/Handler/Concerns/IncludesData.php
@@ -2,7 +2,9 @@
 
 namespace Tobyz\JsonApiServer\Handler\Concerns;
 
+use Closure;
 use Psr\Http\Message\ServerRequestInterface as Request;
+use function Tobyz\JsonApiServer\evaluate;
 use Tobyz\JsonApiServer\Exception\BadRequestException;
 use Tobyz\JsonApiServer\ResourceType;
 use Tobyz\JsonApiServer\Schema\HasMany;
@@ -47,18 +49,18 @@ trait IncludesData
 
     private function validateInclude(ResourceType $resource, array $include, string $path = '')
     {
-        $schema = $resource->getSchema();
+        $fields = $resource->getSchema()->getFields();
 
         foreach ($include as $name => $nested) {
-            if (! isset($schema->fields[$name])
-                || ! $schema->fields[$name] instanceof Relationship
-                || ($schema->fields[$name] instanceof HasMany && ! $schema->fields[$name]->includable)
+            if (! isset($fields[$name])
+                || ! $fields[$name] instanceof Relationship
+                || ! $fields[$name]->isIncludable()
             ) {
                 throw new BadRequestException("Invalid include [{$path}{$name}]", 'include');
             }
 
-            if ($schema->fields[$name]->resource) {
-                $relatedResource = $this->api->getResource($schema->fields[$name]->resource);
+            if ($type = $fields[$name]->getType()) {
+                $relatedResource = $this->api->getResource($type);
 
                 $this->validateInclude($relatedResource, $nested, $name.'.');
             } elseif ($nested) {
@@ -69,18 +71,18 @@ trait IncludesData
 
     private function buildRelationshipTrails(ResourceType $resource, array $include): array
     {
-        $schema = $resource->getSchema();
+        $fields = $resource->getSchema()->getFields();
         $trails = [];
 
         foreach ($include as $name => $nested) {
-            $relationship = $schema->fields[$name];
+            $relationship = $fields[$name];
 
-            if ($relationship->loadable) {
+            if ($relationship->getLoadable()) {
                 $trails[] = [$relationship];
             }
 
-            if ($schema->fields[$name]->resource) {
-                $relatedResource = $this->api->getResource($relationship->resource);
+            if ($type = $fields[$name]->getType()) {
+                $relatedResource = $this->api->getResource($type);
 
                 $trails = array_merge(
                     $trails,
@@ -100,15 +102,15 @@ trait IncludesData
     private function loadRelationships(array $models, array $include, Request $request)
     {
         $adapter = $this->resource->getAdapter();
-        $schema = $this->resource->getSchema();
+        $fields = $this->resource->getSchema()->getFields();
 
-        foreach ($schema->fields as $name => $field) {
-            if (! $field instanceof Relationship || ! ($field->linkage)($request) || ! $field->loadable) {
+        foreach ($fields as $name => $field) {
+            if (! $field instanceof Relationship || ! evaluate($field->getLinkage(), [$request]) || ! $field->getLoadable()) {
                 continue;
             }
 
-            if ($field->loader) {
-                ($field->loader)($models, true);
+            if (($load = $field->getLoadable()) instanceof Closure) {
+                $load($models, true);
             } else {
                 $adapter->loadIds($models, $field);
             }
@@ -117,9 +119,9 @@ trait IncludesData
         $trails = $this->buildRelationshipTrails($this->resource, $include);
 
         foreach ($trails as $relationships) {
-            if ($loader = end($relationships)->loader) {
+            if (($load = end($relationships)->getLoadable()) instanceof Closure) {
                 // TODO: probably need to loop through relationships here
-                ($loader)($models, false);
+                $load($models, false);
             } else {
                 $adapter->load($models, $relationships);
             }
diff --git a/src/Handler/Concerns/SavesData.php b/src/Handler/Concerns/SavesData.php
index abc5a8f..795081f 100644
--- a/src/Handler/Concerns/SavesData.php
+++ b/src/Handler/Concerns/SavesData.php
@@ -3,42 +3,21 @@
 namespace Tobyz\JsonApiServer\Handler\Concerns;
 
 use Psr\Http\Message\ServerRequestInterface as Request;
+use function Tobyz\JsonApiServer\evaluate;
+use function Tobyz\JsonApiServer\get_value;
+use function Tobyz\JsonApiServer\has_value;
 use Tobyz\JsonApiServer\Exception\BadRequestException;
 use Tobyz\JsonApiServer\Exception\UnprocessableEntityException;
-use Tobyz\JsonApiServer\ResourceType;
-use Tobyz\JsonApiServer\Schema;
+use function Tobyz\JsonApiServer\run_callbacks;
+use Tobyz\JsonApiServer\Schema\Attribute;
+use Tobyz\JsonApiServer\Schema\HasMany;
+use Tobyz\JsonApiServer\Schema\HasOne;
+use Tobyz\JsonApiServer\Schema\Relationship;
 
 trait SavesData
 {
     use FindsResources;
 
-    private function save($model, Request $request, bool $creating = false): void
-    {
-        $data = $this->parseData($request->getParsedBody());
-
-        $adapter = $this->resource->getAdapter();
-
-        $this->assertFieldsExist($data);
-
-        $this->assertFieldsWritable($data, $model, $request);
-
-        if ($creating) {
-            $this->fillDefaultValues($data, $request);
-        }
-
-        $this->loadRelatedResources($data, $request);
-
-        $this->assertDataValid($data, $model, $request, $creating);
-
-        $this->applyValues($data, $model, $request);
-
-        $this->saveModel($model, $request);
-
-        $this->saveFields($data, $model, $request);
-
-        $this->runSavedCallbacks($data, $model, $request);
-    }
-
     private function parseData($body): array
     {
         if (! is_array($body) && ! is_object($body)) {
@@ -80,15 +59,19 @@ trait SavesData
         return $this->findResource($request, $resource, $identifier['id']);
     }
 
+    private function validateFields(array $data, $model, Request $request)
+    {
+        $this->assertFieldsExist($data);
+        $this->assertFieldsWritable($data, $model, $request);
+    }
+
     private function assertFieldsExist(array $data)
     {
-        $schema = $this->resource->getSchema();
+        $fields = $this->resource->getSchema()->getFields();
 
         foreach (['attributes', 'relationships'] as $location) {
             foreach ($data[$location] as $name => $value) {
-                if (! isset($schema->fields[$name])
-                    || $location !== $schema->fields[$name]->location
-                ) {
+                if (! isset($fields[$name]) || $location !== $fields[$name]->getLocation()) {
                     throw new BadRequestException("Unknown field [$name]");
                 }
             }
@@ -97,52 +80,29 @@ trait SavesData
 
     private function assertFieldsWritable(array $data, $model, Request $request)
     {
-        $schema = $this->resource->getSchema();
-
-        foreach ($schema->fields as $name => $field) {
-            $valueProvided = isset($data[$field->location][$name]);
-
-            if ($valueProvided && ! ($field->isWritable)($request, $model)) {
-                throw new BadRequestException("Field [$name] is not writable");
-            }
-        }
-    }
-
-    private function fillDefaultValues(array &$data, Request $request)
-    {
-        $schema = $this->resource->getSchema();
-
-        foreach ($schema->fields as $name => $field) {
-            $valueProvided = isset($data[$field->location][$name]);
-
-            if (! $valueProvided && $field->default) {
-                $data[$field->location][$name] = ($field->default)($request);
+        foreach ($this->resource->getSchema()->getFields() as $field) {
+            if (has_value($data, $field) && ! evaluate($field->getWritable(), [$model, $request])) {
+                throw new BadRequestException("Field [{$field->getName()}] is not writable");
             }
         }
     }
 
     private function loadRelatedResources(array &$data, Request $request)
     {
-        $schema = $this->resource->getSchema();
-
-        foreach ($schema->fields as $name => $field) {
-            if (! isset($data[$field->location][$name])) {
+        foreach ($this->resource->getSchema()->getFields() as $field) {
+            if (! $field instanceof Relationship || ! has_value($data, $field)) {
                 continue;
             }
 
-            $value = &$data[$field->location][$name];
+            $value = &get_value($data, $field);
 
-            if ($field instanceof Schema\Relationship) {
-                $value = $value['data'];
-
-                if ($value) {
-                    if ($field instanceof Schema\HasOne) {
-                        $value = $this->getModelForIdentifier($request, $value);
-                    } elseif ($field instanceof Schema\HasMany) {
-                        $value = array_map(function ($identifier) use ($request) {
-                            return $this->getModelForIdentifier($request, $identifier);
-                        }, $value);
-                    }
+            if (isset($value['data'])) {
+                if ($field instanceof HasOne) {
+                    $value = $this->getModelForIdentifier($request, $value['data']);
+                } elseif ($field instanceof HasMany) {
+                    $value = array_map(function ($identifier) use ($request) {
+                        return $this->getModelForIdentifier($request, $identifier);
+                    }, $value['data']);
                 }
             }
         }
@@ -150,22 +110,21 @@ trait SavesData
 
     private function assertDataValid(array $data, $model, Request $request, bool $all): void
     {
-        $schema = $this->resource->getSchema();
-
         $failures = [];
 
-        foreach ($schema->fields as $name => $field) {
-            if (! $all && ! isset($data[$field->location][$name])) {
+        foreach ($this->resource->getSchema()->getFields() as $field) {
+            if (! $all && ! has_value($data, $field)) {
                 continue;
             }
 
-            $fail = function ($message) use (&$failures, $field) {
+            $fail = function ($message = null) use (&$failures, $field) {
                 $failures[] = compact('field', 'message');
             };
 
-            foreach ($field->validators as $validator) {
-                $validator($fail, $data[$field->location][$name] ?? null, $model, $request, $field);
-            }
+            run_callbacks(
+                $field->getListeners('validate'),
+                [$fail, get_value($data, $field), $model, $request, $field]
+            );
         }
 
         if (count($failures)) {
@@ -173,78 +132,81 @@ trait SavesData
         }
     }
 
-    private function applyValues(array $data, $model, Request $request)
+    private function setValues(array $data, $model, Request $request)
     {
-        $schema = $this->resource->getSchema();
         $adapter = $this->resource->getAdapter();
 
-        foreach ($schema->fields as $name => $field) {
-            if (! isset($data[$field->location][$name])) {
+        foreach ($this->resource->getSchema()->getFields() as $field) {
+            if (! has_value($data, $field)) {
                 continue;
             }
 
-            $value = $data[$field->location][$name];
-
-            if ($field->setter || $field->saver) {
-                if ($field->setter) {
-                    ($field->setter)($request, $model, $value);
-                }
+            $value = get_value($data, $field);
 
+            if ($setter = $field->getSetter()) {
+                $setter($model, $value, $request);
                 continue;
             }
 
-            if ($field instanceof Schema\Attribute) {
-                $adapter->applyAttribute($model, $field, $value);
-            } elseif ($field instanceof Schema\HasOne) {
-                $adapter->applyHasOne($model, $field, $value);
+            if ($field->getSaver()) {
+                continue;
+            }
+
+            if ($field instanceof Attribute) {
+                $adapter->setAttribute($model, $field, $value);
+            } elseif ($field instanceof HasOne) {
+                $adapter->setHasOne($model, $field, $value);
             }
         }
     }
 
+    private function save(array $data, $model, Request $request)
+    {
+        $this->saveModel($model, $request);
+        $this->saveFields($data, $model, $request);
+    }
+
     private function saveModel($model, Request $request)
     {
-        $adapter = $this->resource->getAdapter();
-        $schema = $this->resource->getSchema();
-
-        if ($schema->saver) {
-            ($schema->saver)($request, $model);
+        if ($saver = $this->resource->getSchema()->getSaver()) {
+            $saver($model, $request);
         } else {
-            $adapter->save($model);
+            $this->resource->getAdapter()->save($model);
         }
     }
 
     private function saveFields(array $data, $model, Request $request)
     {
-        $schema = $this->resource->getSchema();
         $adapter = $this->resource->getAdapter();
 
-        foreach ($schema->fields as $name => $field) {
-            if (! isset($data[$field->location][$name])) {
+        foreach ($this->resource->getSchema()->getFields() as $field) {
+            if (! has_value($data, $field)) {
                 continue;
             }
 
-            $value = $data[$field->location][$name];
+            $value = get_value($data, $field);
 
-            if ($field->saver) {
-                ($field->saver)($request, $model, $value);
-            } elseif ($field instanceof Schema\HasMany) {
+            if ($saver = $field->getSaver()) {
+                $saver($model, $value, $request);
+            } elseif ($field instanceof HasMany) {
                 $adapter->saveHasMany($model, $field, $value);
             }
         }
+
+        $this->runSavedCallbacks($data, $model, $request);
     }
 
     private function runSavedCallbacks(array $data, $model, Request $request)
     {
-        $schema = $this->resource->getSchema();
-
-        foreach ($schema->fields as $name => $field) {
-            if (! isset($data[$field->location][$name])) {
+        foreach ($this->resource->getSchema()->getFields() as $field) {
+            if (! has_value($data, $field)) {
                 continue;
             }
 
-            foreach ($field->savedCallbacks as $callback) {
-                $callback($request, $model, $data[$field->location][$name]);
-            }
+            run_callbacks(
+                $field->getListeners('saved'),
+                [$model, get_value($data, $field), $request]
+            );
         }
     }
 }
diff --git a/src/Handler/Create.php b/src/Handler/Create.php
index 69d9b76..33bb2bb 100644
--- a/src/Handler/Create.php
+++ b/src/Handler/Create.php
@@ -5,9 +5,13 @@ namespace Tobyz\JsonApiServer\Handler;
 use Psr\Http\Message\ResponseInterface as Response;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Psr\Http\Server\RequestHandlerInterface;
-use Tobyz\JsonApiServer\Api;
+use function Tobyz\JsonApiServer\evaluate;
+use function Tobyz\JsonApiServer\has_value;
+use Tobyz\JsonApiServer\JsonApi;
 use Tobyz\JsonApiServer\Exception\ForbiddenException;
 use Tobyz\JsonApiServer\ResourceType;
+use function Tobyz\JsonApiServer\run_callbacks;
+use function Tobyz\JsonApiServer\set_value;
 
 class Create implements RequestHandlerInterface
 {
@@ -16,7 +20,7 @@ class Create implements RequestHandlerInterface
     private $api;
     private $resource;
 
-    public function __construct(Api $api, ResourceType $resource)
+    public function __construct(JsonApi $api, ResourceType $resource)
     {
         $this->api = $api;
         $this->resource = $resource;
@@ -26,44 +30,43 @@ class Create implements RequestHandlerInterface
     {
         $schema = $this->resource->getSchema();
 
-        if (! ($schema->isCreatable)($request)) {
-            throw new ForbiddenException('You cannot create this resource');
+        if (! evaluate($schema->getCreatable(), [$request])) {
+            throw new ForbiddenException;
         }
 
-        $model = $schema->createModel ? ($schema->createModel)($request) : $this->resource->getAdapter()->create();
-
+        $model = $this->createModel($request);
         $data = $this->parseData($request->getParsedBody());
 
-        $adapter = $this->resource->getAdapter();
-
-        $this->assertFieldsExist($data);
-
-        $this->assertFieldsWritable($data, $model, $request);
-
+        $this->validateFields($data, $model, $request);
         $this->fillDefaultValues($data, $request);
-
         $this->loadRelatedResources($data, $request);
-
         $this->assertDataValid($data, $model, $request, true);
+        $this->setValues($data, $model, $request);
 
-        $this->applyValues($data, $model, $request);
+        run_callbacks($schema->getListeners('creating'), [$request, $model]);
 
-        foreach ($schema->creatingCallbacks as $callback) {
-            $callback($request, $model);
-        }
+        $this->save($data, $model, $request);
 
-        $this->saveModel($model, $request);
-
-        $this->saveFields($data, $model, $request);
-
-        $this->runSavedCallbacks($data, $model, $request);
-
-        foreach ($schema->createdCallbacks as $callback) {
-            $callback($request, $model);
-        }
+        run_callbacks($schema->getListeners('created'), [$request, $model]);
 
         return (new Show($this->api, $this->resource, $model))
             ->handle($request)
             ->withStatus(201);
     }
+
+    private function createModel(Request $request)
+    {
+        $creator = $this->resource->getSchema()->getCreator();
+
+        return $creator ? $creator($request) : $this->resource->getAdapter()->create();
+    }
+
+    private function fillDefaultValues(array &$data, Request $request)
+    {
+        foreach ($this->resource->getSchema()->getFields() as $field) {
+            if (! has_value($data, $field) && ($default = $field->getDefault())) {
+                set_value($data, $field, $default($request));
+            }
+        }
+    }
 }
diff --git a/src/Handler/Delete.php b/src/Handler/Delete.php
index bd7aae4..7a782ce 100644
--- a/src/Handler/Delete.php
+++ b/src/Handler/Delete.php
@@ -5,8 +5,10 @@ namespace Tobyz\JsonApiServer\Handler;
 use Psr\Http\Message\ResponseInterface as Response;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Psr\Http\Server\RequestHandlerInterface;
+use function Tobyz\JsonApiServer\evaluate;
 use Tobyz\JsonApiServer\Exception\ForbiddenException;
 use Tobyz\JsonApiServer\ResourceType;
+use function Tobyz\JsonApiServer\run_callbacks;
 use Zend\Diactoros\Response\EmptyResponse;
 
 class Delete implements RequestHandlerInterface
@@ -24,19 +26,15 @@ class Delete implements RequestHandlerInterface
     {
         $schema = $this->resource->getSchema();
 
-        if (! ($schema->isDeletable)($request, $this->model)) {
-            throw new ForbiddenException('You cannot delete this resource');
+        if (! evaluate($schema->getDeletable(), [$request, $this->model])) {
+            throw new ForbiddenException;
         }
 
-        foreach ($schema->deletingCallbacks as $callback) {
-            $callback($request, $this->model);
-        }
+        run_callbacks($schema->getListeners('deleting'), [$request, $this->model]);
 
         $this->resource->getAdapter()->delete($this->model);
 
-        foreach ($schema->deletedCallbacks as $callback) {
-            $callback($request, $this->model);
-        }
+        run_callbacks($schema->getListeners('deleted'), [$request, $this->model]);
 
         return new EmptyResponse;
     }
diff --git a/src/Handler/Index.php b/src/Handler/Index.php
index 864f0a7..71a5723 100644
--- a/src/Handler/Index.php
+++ b/src/Handler/Index.php
@@ -2,18 +2,24 @@
 
 namespace Tobyz\JsonApiServer\Handler;
 
-use JsonApiPhp\JsonApi;
-use JsonApiPhp\JsonApi\Link;
+use Closure;
+use JsonApiPhp\JsonApi as Structure;
+use JsonApiPhp\JsonApi\Link\LastLink;
+use JsonApiPhp\JsonApi\Link\NextLink;
+use JsonApiPhp\JsonApi\Link\PrevLink;
 use JsonApiPhp\JsonApi\Meta;
 use Psr\Http\Message\ResponseInterface as Response;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Psr\Http\Server\RequestHandlerInterface;
-use Tobyz\JsonApiServer\Api;
+use Tobyz\JsonApiServer\JsonApi;
 use Tobyz\JsonApiServer\Exception\BadRequestException;
 use Tobyz\JsonApiServer\Exception\ForbiddenException;
 use Tobyz\JsonApiServer\JsonApiResponse;
 use Tobyz\JsonApiServer\ResourceType;
-use Tobyz\JsonApiServer\Schema;
+use Tobyz\JsonApiServer\Schema\Attribute;
+use Tobyz\JsonApiServer\Schema\HasMany;
+use Tobyz\JsonApiServer\Schema\HasOne;
+use Tobyz\JsonApiServer\Schema\Type;
 use Tobyz\JsonApiServer\Serializer;
 
 class Index implements RequestHandlerInterface
@@ -23,7 +29,7 @@ class Index implements RequestHandlerInterface
     private $api;
     private $resource;
 
-    public function __construct(Api $api, ResourceType $resource)
+    public function __construct(JsonApi $api, ResourceType $resource)
     {
         $this->api = $api;
         $this->resource = $resource;
@@ -38,13 +44,9 @@ class Index implements RequestHandlerInterface
         $adapter = $this->resource->getAdapter();
         $schema = $this->resource->getSchema();
 
-        if (! ($schema->isVisible)($request)) {
-            throw new ForbiddenException('You cannot view this resource');
-        }
-
         $query = $adapter->query();
 
-        foreach ($schema->scopes as $scope) {
+        foreach ($schema->getScopes() as $scope) {
             $request = $scope($request, $query) ?: $request;
         }
 
@@ -58,13 +60,13 @@ class Index implements RequestHandlerInterface
 
         $paginationLinks = [];
         $members = [
-            new Link\SelfLink($this->buildUrl($request)),
-            new Meta('offset', $offset),
-            new Meta('limit', $limit),
+            new Structure\Link\SelfLink($this->buildUrl($request)),
+            new Structure\Meta('offset', $offset),
+            new Structure\Meta('limit', $limit),
         ];
 
         if ($offset > 0) {
-            $paginationLinks[] = new Link\FirstLink($this->buildUrl($request, ['page' => ['offset' => 0]]));
+            $paginationLinks[] = new Structure\Link\FirstLink($this->buildUrl($request, ['page' => ['offset' => 0]]));
 
             $prevOffset = $offset - $limit;
 
@@ -74,16 +76,16 @@ class Index implements RequestHandlerInterface
                 $params = ['page' => ['offset' => max(0, $prevOffset)]];
             }
 
-            $paginationLinks[] = new Link\PrevLink($this->buildUrl($request, $params));
+            $paginationLinks[] = new PrevLink($this->buildUrl($request, $params));
         }
 
-        if ($schema->countable && $schema->paginate) {
+        if ($schema->isCountable() && $schema->getPaginate()) {
             $total = $adapter->count($query);
 
             $members[] = new Meta('total', $total);
 
             if ($offset + $limit < $total) {
-                $paginationLinks[] = new Link\LastLink($this->buildUrl($request, ['page' => ['offset' => floor(($total - 1) / $limit) * $limit]]));
+                $paginationLinks[] = new LastLink($this->buildUrl($request, ['page' => ['offset' => floor(($total - 1) / $limit) * $limit]]));
             }
         }
 
@@ -96,7 +98,7 @@ class Index implements RequestHandlerInterface
         $models = $adapter->get($query);
 
         if ((count($models) && $total === null) || $offset + $limit < $total) {
-            $paginationLinks[] = new Link\NextLink($this->buildUrl($request, ['page' => ['offset' => $offset + $limit]]));
+            $paginationLinks[] = new NextLink($this->buildUrl($request, ['page' => ['offset' => $offset + $limit]]));
         }
 
         $this->loadRelationships($models, $include, $request);
@@ -108,12 +110,12 @@ class Index implements RequestHandlerInterface
         }
 
         return new JsonApiResponse(
-            new JsonApi\CompoundDocument(
-                new JsonApi\PaginatedCollection(
-                    new JsonApi\Pagination(...$paginationLinks),
-                    new JsonApi\ResourceCollection(...$serializer->primary())
+            new Structure\CompoundDocument(
+                new Structure\PaginatedCollection(
+                    new Structure\Pagination(...$paginationLinks),
+                    new Structure\ResourceCollection(...$serializer->primary())
                 ),
-                new JsonApi\Included(...$serializer->included()),
+                new Structure\Included(...$serializer->included()),
                 ...$members
             )
         );
@@ -149,7 +151,7 @@ class Index implements RequestHandlerInterface
 
         $queryParams = $request->getQueryParams();
 
-        $limit = $this->resource->getSchema()->paginate;
+        $limit = $this->resource->getSchema()->getPaginate();
 
         if (isset($queryParams['page']['limit'])) {
             $limit = $queryParams['page']['limit'];
@@ -158,7 +160,7 @@ class Index implements RequestHandlerInterface
                 throw new BadRequestException('page[limit] must be a positive integer', 'page[limit]');
             }
 
-            $limit = min($this->resource->getSchema()->limit, $limit);
+            $limit = min($this->resource->getSchema()->getLimit(), $limit);
         }
 
         $offset = 0;
@@ -175,15 +177,16 @@ class Index implements RequestHandlerInterface
             ->withAttribute('jsonApiLimit', $limit)
             ->withAttribute('jsonApiOffset', $offset);
 
-        $sort = $queryParams['sort'] ?? $this->resource->getSchema()->defaultSort;
+        $sort = $queryParams['sort'] ?? $this->resource->getSchema()->getDefaultSort();
 
         if ($sort) {
             $sort = $this->parseSort($sort);
+            $fields = $schema->getFields();
 
             foreach ($sort as $name => $direction) {
-                if (! isset($schema->fields[$name])
-                    || ! $schema->fields[$name] instanceof Schema\Attribute
-                    || ! $schema->fields[$name]->sortable
+                if (! isset($fields[$name])
+                    || ! $fields[$name] instanceof Attribute
+                    || ! $fields[$name]->getSortable()
                 ) {
                     throw new BadRequestException("Invalid sort field [$name]", 'sort');
                 }
@@ -199,8 +202,10 @@ class Index implements RequestHandlerInterface
                 throw new BadRequestException('filter must be an array', 'filter');
             }
 
+            $fields = $schema->getFields();
+
             foreach ($filter as $name => $value) {
-                if ($name !== 'id' && (! isset($schema->fields[$name]) || ! $schema->fields[$name]->filterable)) {
+                if ($name !== 'id' && (! isset($fields[$name]) || ! $fields[$name]->getFilterable())) {
                     throw new BadRequestException("Invalid filter [$name]", "filter[$name]");
                 }
             }
@@ -217,10 +222,10 @@ class Index implements RequestHandlerInterface
         $adapter = $this->resource->getAdapter();
 
         foreach ($sort as $name => $direction) {
-            $attribute = $schema->fields[$name];
+            $attribute = $schema->getFields()[$name];
 
-            if ($attribute->sorter) {
-                ($attribute->sorter)($request, $query, $direction);
+            if (($sorter = $attribute->getSortable()) instanceof Closure) {
+                $sorter($query, $direction, $request);
             } else {
                 $adapter->sortByAttribute($query, $attribute, $direction);
             }
@@ -267,16 +272,16 @@ class Index implements RequestHandlerInterface
                 continue;
             }
 
-            $field = $schema->fields[$name];
+            $field = $schema->getFields()[$name];
 
-            if ($field->filter) {
-                ($field->filter)($query, $value, $request);
-            } elseif ($field instanceof Schema\Attribute) {
+            if (($filter = $field->getFilterable()) instanceof Closure) {
+                $filter($query, $value, $request);
+            } elseif ($field instanceof Attribute) {
                 $adapter->filterByAttribute($query, $field, $value);
-            } elseif ($field instanceof Schema\HasOne) {
+            } elseif ($field instanceof HasOne) {
                 $value = explode(',', $value);
                 $adapter->filterByHasOne($query, $field, $value);
-            } elseif ($field instanceof Schema\HasMany) {
+            } elseif ($field instanceof HasMany) {
                 $value = explode(',', $value);
                 $adapter->filterByHasMany($query, $field, $value);
             }
diff --git a/src/Handler/Show.php b/src/Handler/Show.php
index 41d72a6..2dbcebd 100644
--- a/src/Handler/Show.php
+++ b/src/Handler/Show.php
@@ -2,12 +2,12 @@
 
 namespace Tobyz\JsonApiServer\Handler;
 
-use JsonApiPhp\JsonApi;
+use JsonApiPhp\JsonApi\CompoundDocument;
+use JsonApiPhp\JsonApi\Included;
 use Psr\Http\Message\ResponseInterface as Response;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Psr\Http\Server\RequestHandlerInterface;
-use Tobyz\JsonApiServer\Api;
-use Tobyz\JsonApiServer\Exception\ForbiddenException;
+use Tobyz\JsonApiServer\JsonApi;
 use Tobyz\JsonApiServer\JsonApiResponse;
 use Tobyz\JsonApiServer\ResourceType;
 use Tobyz\JsonApiServer\Serializer;
@@ -20,7 +20,7 @@ class Show implements RequestHandlerInterface
     private $resource;
     private $model;
 
-    public function __construct(Api $api, ResourceType $resource, $model)
+    public function __construct(JsonApi $api, ResourceType $resource, $model)
     {
         $this->api = $api;
         $this->resource = $resource;
@@ -29,12 +29,6 @@ class Show implements RequestHandlerInterface
 
     public function handle(Request $request): Response
     {
-        $schema = $this->resource->getSchema();
-
-        if (! ($schema->isVisible)($request)) {
-            throw new ForbiddenException('You cannot view this resource');
-        }
-
         $include = $this->getInclude($request);
 
         $this->loadRelationships([$this->model], $include, $request);
@@ -44,9 +38,9 @@ class Show implements RequestHandlerInterface
         $serializer->add($this->resource, $this->model, $include);
 
         return new JsonApiResponse(
-            new JsonApi\CompoundDocument(
+            new CompoundDocument(
                 $serializer->primary()[0],
-                new JsonApi\Included(...$serializer->included())
+                new Included(...$serializer->included())
             )
         );
     }
diff --git a/src/Handler/Update.php b/src/Handler/Update.php
index 7a488c3..373c83e 100644
--- a/src/Handler/Update.php
+++ b/src/Handler/Update.php
@@ -5,9 +5,11 @@ namespace Tobyz\JsonApiServer\Handler;
 use Psr\Http\Message\ResponseInterface as Response;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Psr\Http\Server\RequestHandlerInterface;
-use Tobyz\JsonApiServer\Api;
+use function Tobyz\JsonApiServer\evaluate;
+use Tobyz\JsonApiServer\JsonApi;
 use Tobyz\JsonApiServer\Exception\ForbiddenException;
 use Tobyz\JsonApiServer\ResourceType;
+use function Tobyz\JsonApiServer\run_callbacks;
 
 class Update implements RequestHandlerInterface
 {
@@ -17,7 +19,7 @@ class Update implements RequestHandlerInterface
     private $resource;
     private $model;
 
-    public function __construct(Api $api, ResourceType $resource, $model)
+    public function __construct(JsonApi $api, ResourceType $resource, $model)
     {
         $this->api = $api;
         $this->resource = $resource;
@@ -28,19 +30,22 @@ class Update implements RequestHandlerInterface
     {
         $schema = $this->resource->getSchema();
 
-        if (! ($schema->isUpdatable)($request, $this->model)) {
-            throw new ForbiddenException('You cannot update this resource');
+        if (! evaluate($schema->getUpdatable(), [$request, $this->model])) {
+            throw new ForbiddenException;
         }
 
-        foreach ($schema->updatingCallbacks as $callback) {
-            $callback($request, $this->model);
-        }
+        $data = $this->parseData($request->getParsedBody());
 
-        $this->save($this->model, $request);
+        $this->validateFields($data, $this->model, $request);
+        $this->loadRelatedResources($data, $request);
+        $this->assertDataValid($data, $this->model, $request, false);
+        $this->setValues($data, $this->model, $request);
 
-        foreach ($schema->updatedCallbacks as $callback) {
-            $callback($request, $this->model);
-        }
+        run_callbacks($schema->getListeners('updating'), [$request, $this->model]);
+
+        $this->save($data, $this->model, $request);
+
+        run_callbacks($schema->getListeners('updated'), [$request, $this->model]);
 
         return (new Show($this->api, $this->resource, $this->model))->handle($request);
     }
diff --git a/src/Http/MediaTypes.php b/src/Http/MediaTypes.php
new file mode 100644
index 0000000..a9cceef
--- /dev/null
+++ b/src/Http/MediaTypes.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace Tobyz\JsonApiServer\Http;
+
+class MediaTypes
+{
+    private $value;
+
+    public function __construct(string $value)
+    {
+        $this->value = $value;
+    }
+
+    /**
+     * Determine whether the list contains the given type without modifications
+     *
+     * This is meant to ease implementation of JSON:API rules for content
+     * negotiation, which demand HTTP error responses e.g. when all of the
+     * JSON:API media types in the "Accept" header are modified with "media type
+     * parameters". Therefore, this method only returns true when the requested
+     * media type is contained without additional parameters (except for the
+     * weight parameter "q" and "Accept extension parameters").
+     *
+     * @param string $mediaType
+     * @return bool
+     */
+    public function containsExactly(string $mediaType): bool
+    {
+        $types = array_map('trim', explode(',', $this->value));
+
+        // Accept headers can contain multiple media types, so we need to check
+        // whether any of them matches.
+        foreach ($types as $type) {
+            $parts = array_map('trim', explode(';', $type));
+
+            // The actual media type needs to be an exact match
+            if (array_shift($parts) !== $mediaType) {
+                continue;
+            }
+
+            // The media type can optionally be followed by "media type
+            // parameters". Parameters after the "q" parameter are considered
+            // "Accept extension parameters", which we don't care about. Thus,
+            // we have an exact match if there are no parameters at all or if
+            // the first one is named "q".
+            // See https://tools.ietf.org/html/rfc7231#section-5.3.2.
+            if (empty($parts) || substr($parts[0], 0, 2) === 'q=') {
+                return true;
+            }
+
+            continue;
+        }
+
+        return false;
+    }
+}
diff --git a/src/JsonApi.php b/src/JsonApi.php
new file mode 100644
index 0000000..81481af
--- /dev/null
+++ b/src/JsonApi.php
@@ -0,0 +1,202 @@
+<?php
+
+namespace Tobyz\JsonApiServer;
+
+use Closure;
+use JsonApiPhp\JsonApi\ErrorDocument;
+use Psr\Http\Message\ResponseInterface as Response;
+use Psr\Http\Message\ServerRequestInterface as Request;
+use Psr\Http\Server\RequestHandlerInterface;
+use Tobyz\JsonApiServer\Exception\BadRequestException;
+use Tobyz\JsonApiServer\Exception\InternalServerErrorException;
+use Tobyz\JsonApiServer\Exception\MethodNotAllowedException;
+use Tobyz\JsonApiServer\Exception\NotAcceptableException;
+use Tobyz\JsonApiServer\Exception\NotImplementedException;
+use Tobyz\JsonApiServer\Exception\ResourceNotFoundException;
+use Tobyz\JsonApiServer\Exception\UnsupportedMediaTypeException;
+use Tobyz\JsonApiServer\Handler\Concerns\FindsResources;
+use Tobyz\JsonApiServer\Http\MediaTypes;
+
+final class JsonApi implements RequestHandlerInterface
+{
+    const CONTENT_TYPE = 'application/vnd.api+json';
+
+    use FindsResources;
+
+    private $resources = [];
+    private $baseUrl;
+
+    public function __construct(string $baseUrl)
+    {
+        $this->baseUrl = $baseUrl;
+    }
+
+    public function resource(string $type, $adapter, Closure $buildSchema = null): void
+    {
+        $this->resources[$type] = new ResourceType($type, $adapter, $buildSchema);
+    }
+
+    public function getResources(): array
+    {
+        return $this->resources;
+    }
+
+    public function getResource(string $type): ResourceType
+    {
+        if (! isset($this->resources[$type])) {
+            throw new ResourceNotFoundException($type);
+        }
+
+        return $this->resources[$type];
+    }
+
+    public function handle(Request $request): Response
+    {
+        $this->validateRequest($request);
+
+        $path = $this->stripBasePath(
+            $request->getUri()->getPath()
+        );
+
+        $segments = explode('/', trim($path, '/'));
+
+        switch (count($segments)) {
+            case 1:
+                return $this->handleWithHandler(
+                    $request,
+                    $this->getCollectionHandler($request, $segments)
+                );
+
+            case 2:
+                return $this->handleWithHandler(
+                    $request,
+                    $this->getMemberHandler($request, $segments)
+                );
+
+            case 3:
+                // return $this->handleRelated($request, $resource, $model, $segments[2]);
+                throw new NotImplementedException;
+
+            case 4:
+                if ($segments[2] === 'relationships') {
+                    // return $this->handleRelationship($request, $resource, $model, $segments[3]);
+                    throw new NotImplementedException;
+                }
+        }
+
+        throw new BadRequestException;
+    }
+
+    private function validateRequest(Request $request): void
+    {
+        $this->validateRequestContentType($request);
+        $this->validateRequestAccepts($request);
+    }
+
+    private function validateRequestContentType(Request $request): void
+    {
+        $header = $request->getHeaderLine('Content-Type');
+
+        if (empty($header)) {
+            return;
+        }
+
+        if ((new MediaTypes($header))->containsExactly(self::CONTENT_TYPE)) {
+            return;
+        }
+
+        throw new UnsupportedMediaTypeException;
+    }
+
+    private function validateRequestAccepts(Request $request): void
+    {
+        $header = $request->getHeaderLine('Accept');
+
+        if (empty($header)) {
+            return;
+        }
+
+        if ((new MediaTypes($header))->containsExactly(self::CONTENT_TYPE)) {
+            return;
+        }
+
+        throw new NotAcceptableException;
+    }
+
+    private function stripBasePath(string $path): string
+    {
+        $basePath = parse_url($this->baseUrl, PHP_URL_PATH);
+
+        $len = strlen($basePath);
+
+        if (substr($path, 0, $len) === $basePath) {
+            $path = substr($path, $len + 1);
+        }
+
+        return $path;
+    }
+
+    private function getCollectionHandler(Request $request, array $segments): RequestHandlerInterface
+    {
+        $resource = $this->getResource($segments[0]);
+
+        switch ($request->getMethod()) {
+            case 'GET':
+                return new Handler\Index($this, $resource);
+
+            case 'POST':
+                return new Handler\Create($this, $resource);
+
+            default:
+                throw new MethodNotAllowedException;
+        }
+    }
+
+    private function getMemberHandler(Request $request, array $segments): RequestHandlerInterface
+    {
+        $resource = $this->getResource($segments[0]);
+        $model = $this->findResource($request, $resource, $segments[1]);
+
+        switch ($request->getMethod()) {
+            case 'PATCH':
+                return new Handler\Update($this, $resource, $model);
+
+            case 'GET':
+                return new Handler\Show($this, $resource, $model);
+
+            case 'DELETE':
+                return new Handler\Delete($resource, $model);
+
+            default:
+                throw new MethodNotAllowedException;
+        }
+    }
+
+    private function handleWithHandler(Request $request, RequestHandlerInterface $handler)
+    {
+        $request = $request->withAttribute('jsonApiHandler', $handler);
+
+        return $handler->handle($request);
+    }
+
+    public function error($e)
+    {
+        if (! $e instanceof ErrorProviderInterface) {
+            $e = new InternalServerErrorException;
+        }
+
+        $errors = $e->getJsonApiErrors();
+        $status = $e->getJsonApiStatus();
+
+        $data = new ErrorDocument(
+            ...$errors
+        );
+
+        return new JsonApiResponse($data, $status);
+    }
+
+    public function getBaseUrl(): string
+    {
+        return $this->baseUrl;
+    }
+}
diff --git a/src/JsonApiResponse.php b/src/JsonApiResponse.php
index 35d1131..62e1814 100644
--- a/src/JsonApiResponse.php
+++ b/src/JsonApiResponse.php
@@ -12,7 +12,7 @@ class JsonApiResponse extends JsonResponse
         array $headers = [],
         $encodingOptions = self::DEFAULT_JSON_FLAGS
     ) {
-        $headers['content-type'] = 'application/vnd.api+json';
+        $headers['content-type'] = JsonApi::CONTENT_TYPE;
 
         parent::__construct($data, $status, $headers, $encodingOptions);
     }
diff --git a/src/ResourceType.php b/src/ResourceType.php
index b7b631b..09f403d 100644
--- a/src/ResourceType.php
+++ b/src/ResourceType.php
@@ -4,14 +4,14 @@ namespace Tobyz\JsonApiServer;
 
 use Closure;
 use Tobyz\JsonApiServer\Adapter\AdapterInterface;
-use Tobyz\JsonApiServer\Schema\Builder;
+use Tobyz\JsonApiServer\Schema\Type;
 
-class ResourceType
+final class ResourceType
 {
-    protected $type;
-    protected $adapter;
-    protected $buildSchema;
-    protected $schema;
+    private $type;
+    private $adapter;
+    private $buildSchema;
+    private $schema;
 
     public function __construct(string $type, AdapterInterface $adapter, Closure $buildSchema = null)
     {
@@ -30,10 +30,10 @@ class ResourceType
         return $this->adapter;
     }
 
-    public function getSchema(): Builder
+    public function getSchema(): Type
     {
         if (! $this->schema) {
-            $this->schema = new Builder;
+            $this->schema = new Type;
 
             if ($this->buildSchema) {
                 ($this->buildSchema)($this->schema);
diff --git a/src/Schema/Attribute.php b/src/Schema/Attribute.php
index a5bbab4..c1608d9 100644
--- a/src/Schema/Attribute.php
+++ b/src/Schema/Attribute.php
@@ -4,17 +4,31 @@ namespace Tobyz\JsonApiServer\Schema;
 
 use Closure;
 
-class Attribute extends Field
+final class Attribute extends Field
 {
-    public $location = 'attributes';
-    public $sortable = false;
-    public $sorter;
+    private $sortable = false;
 
     public function sortable(Closure $callback = null)
     {
-        $this->sortable = true;
-        $this->sorter = $callback;
+        $this->sortable = $callback ?: true;
 
         return $this;
     }
+
+    public function notSortable()
+    {
+        $this->sortable = false;
+
+        return $this;
+    }
+
+    public function getSortable()
+    {
+        return $this->sortable;
+    }
+
+    public function getLocation(): string
+    {
+        return 'attributes';
+    }
 }
diff --git a/src/Schema/Builder.php b/src/Schema/Builder.php
deleted file mode 100644
index e6273ea..0000000
--- a/src/Schema/Builder.php
+++ /dev/null
@@ -1,241 +0,0 @@
-<?php
-
-namespace Tobyz\JsonApiServer\Schema;
-
-use Closure;
-
-class Builder
-{
-    public $fields = [];
-    public $meta = [];
-    public $paginate = 20;
-    public $limit = 50;
-    public $countable = true;
-    public $scopes = [];
-    public $isCreatable;
-    public $creatingCallbacks = [];
-    public $createdCallbacks = [];
-    public $isUpdatable;
-    public $updatingCallbacks = [];
-    public $updatedCallbacks = [];
-    public $isDeletable;
-    public $deletingCallbacks = [];
-    public $deletedCallbacks = [];
-    public $defaultSort;
-    public $createModel;
-    public $saver;
-
-    public function __construct()
-    {
-        $this->visible();
-        $this->notCreatable();
-        $this->notUpdatable();
-        $this->notDeletable();
-    }
-
-    public function attribute(string $name, string $property = null): Attribute
-    {
-        return $this->field(Attribute::class, $name, $property);
-    }
-
-    public function hasOne(string $name, $resource = null, string $property = null): HasOne
-    {
-        $field = $this->field(HasOne::class, $name, $property);
-
-        if ($resource) {
-            $field->resource($resource);
-        }
-
-        return $field;
-    }
-
-    public function morphOne(string $name, string $property = null): HasOne
-    {
-        return $this->field(HasOne::class, $name, $property)->resource(null);
-    }
-
-    public function hasMany(string $name, $resource = null, string $property = null): HasMany
-    {
-        $field = $this->field(HasMany::class, $name, $property);
-
-        if ($resource) {
-            $field->resource($resource);
-        }
-
-        return $field;
-    }
-
-    public function meta(string $name, $value)
-    {
-        return $this->meta[$name] = new Meta($name, $value);
-    }
-
-    public function paginate(?int $perPage)
-    {
-        $this->paginate = $perPage;
-    }
-
-    public function limit(?int $limit)
-    {
-        $this->limit = $limit;
-    }
-
-    public function countable()
-    {
-        $this->countable = true;
-    }
-
-    public function uncountable()
-    {
-        $this->countable = false;
-    }
-
-    public function createModel(Closure $callback)
-    {
-        $this->createModel = $callback;
-    }
-
-    public function scope(Closure $callback)
-    {
-        $this->scopes[] = $callback;
-    }
-
-    public function creatableIf(Closure $condition)
-    {
-        $this->isCreatable = $condition;
-
-        return $this;
-    }
-
-    public function creatable()
-    {
-        return $this->creatableIf(function () {
-            return true;
-        });
-    }
-
-    public function notCreatableIf(Closure $condition)
-    {
-        return $this->creatableIf(function (...$args) use ($condition) {
-            return ! $condition(...$args);
-        });
-    }
-
-    public function notCreatable()
-    {
-        return $this->notCreatableIf(function () {
-            return true;
-        });
-    }
-
-    public function creating(Closure $callback)
-    {
-        $this->creatingCallbacks[] = $callback;
-    }
-
-    public function created(Closure $callback)
-    {
-        $this->createdCallbacks[] = $callback;
-    }
-
-    public function updatableIf(Closure $condition)
-    {
-        $this->isUpdatable = $condition;
-
-        return $this;
-    }
-
-    public function updatable()
-    {
-        return $this->updatableIf(function () {
-            return true;
-        });
-    }
-
-    public function notUpdatableIf(Closure $condition)
-    {
-        return $this->updatableIf(function (...$args) use ($condition) {
-            return ! $condition(...$args);
-        });
-    }
-
-    public function notUpdatable()
-    {
-        return $this->notUpdatableIf(function () {
-            return true;
-        });
-    }
-
-    public function updating(Closure $callback)
-    {
-        $this->updatingCallbacks[] = $callback;
-    }
-
-    public function updated(Closure $callback)
-    {
-        $this->updatedCallbacks[] = $callback;
-    }
-
-    public function save(Closure $callback)
-    {
-        $this->saver = $callback;
-
-        return $this;
-    }
-
-    public function deletableIf(Closure $condition)
-    {
-        $this->isDeletable = $condition;
-
-        return $this;
-    }
-
-    public function deletable()
-    {
-        return $this->deletableIf(function () {
-            return true;
-        });
-    }
-
-    public function notDeletableIf(Closure $condition)
-    {
-        return $this->deletableIf(function (...$args) use ($condition) {
-            return ! $condition(...$args);
-        });
-    }
-
-    public function notDeletable()
-    {
-        return $this->notDeletableIf(function () {
-            return true;
-        });
-    }
-
-    public function deleting(Closure $callback)
-    {
-        $this->deletingCallbacks[] = $callback;
-    }
-
-    public function deleted(Closure $callback)
-    {
-        $this->deletedCallbacks[] = $callback;
-    }
-
-    public function defaultSort(string $sort)
-    {
-        $this->defaultSort = $sort;
-    }
-
-    private function field(string $class, string $name, string $property = null)
-    {
-        if (! isset($this->fields[$name]) || ! $this->fields[$name] instanceof $class) {
-            $this->fields[$name] = new $class($name);
-        }
-
-        if ($property) {
-            $this->fields[$name]->property($property);
-        }
-
-        return $this->fields[$name];
-    }
-}
diff --git a/src/Schema/Concerns/HasListeners.php b/src/Schema/Concerns/HasListeners.php
new file mode 100644
index 0000000..82e25b8
--- /dev/null
+++ b/src/Schema/Concerns/HasListeners.php
@@ -0,0 +1,22 @@
+<?php
+
+/*
+ * This file is part of tobyz/json-api-server.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Tobyz\JsonApiServer\Schema\Concerns;
+
+trait HasListeners
+{
+    private $listeners = [];
+
+    public function getListeners(string $event)
+    {
+        return $this->listeners[$event] ?? [];
+    }
+}
diff --git a/src/Schema/Field.php b/src/Schema/Field.php
index 90b832d..aacb63c 100644
--- a/src/Schema/Field.php
+++ b/src/Schema/Field.php
@@ -3,30 +3,31 @@
 namespace Tobyz\JsonApiServer\Schema;
 
 use Closure;
+use function Tobyz\JsonApiServer\negate;
+use Tobyz\JsonApiServer\Schema\Concerns\HasListeners;
+use function Tobyz\JsonApiServer\wrap;
 
 abstract class Field
 {
-    public $name;
-    public $property;
-    public $isVisible;
-    public $isWritable;
-    public $getter;
-    public $setter;
-    public $saver;
-    public $savedCallbacks = [];
-    public $default;
-    public $validators = [];
-    public $filterable = false;
-    public $filter;
+    use HasListeners;
+
+    private $name;
+    private $property;
+    private $visible = true;
+    private $writable = false;
+    private $getter;
+    private $setter;
+    private $saver;
+    private $default;
+    private $filterable = false;
 
     public function __construct(string $name)
     {
         $this->name = $name;
-
-        $this->visible();
-        $this->readonly();
     }
 
+    abstract public function getLocation(): string;
+
     public function property(string $property)
     {
         $this->property = $property;
@@ -34,65 +35,37 @@ abstract class Field
         return $this;
     }
 
-    public function visibleIf(Closure $condition)
+    public function visible(Closure $condition = null)
     {
-        $this->isVisible = $condition;
+        $this->visible = $condition ?: true;
 
         return $this;
     }
 
-    public function visible()
+    public function hidden(Closure $condition = null)
     {
-        return $this->visibleIf(function () {
-            return true;
-        });
-    }
-
-    public function hiddenIf(Closure $condition)
-    {
-        return $this->visibleIf(function (...$args) use ($condition) {
-            return ! $condition(...$args);
-        });
-    }
-
-    public function hidden()
-    {
-        return $this->hiddenIf(function () {
-            return true;
-        });
-    }
-
-    public function writableIf(Closure $condition)
-    {
-        $this->isWritable = $condition;
+        $this->visible = $condition ? negate($condition) : false;
 
         return $this;
     }
 
-    public function writable()
+    public function writable(Closure $condition = null)
     {
-        return $this->writableIf(function () {
-            return true;
-        });
+        $this->writable = $condition ?: true;
+
+        return $this;
     }
 
-    public function readonlyIf(Closure $condition)
+    public function readonly(Closure $condition = null)
     {
-        return $this->writableIf(function (...$args) use ($condition) {
-            return ! $condition(...$args);
-        });
+        $this->writable = $condition ? negate($condition) : false;
+
+        return $this;
     }
 
-    public function readonly()
+    public function get($value)
     {
-        return $this->readonlyIf(function () {
-            return true;
-        });
-    }
-
-    public function get($callback)
-    {
-        $this->getter = $this->wrap($callback);
+        $this->getter = wrap($value);
 
         return $this;
     }
@@ -113,41 +86,86 @@ abstract class Field
 
     public function saved(Closure $callback)
     {
-        $this->savedCallbacks[] = $callback;
+        $this->listeners['saved'][] = $callback;
 
         return $this;
     }
 
     public function default($value)
     {
-        $this->default = $this->wrap($value);
+        $this->default = wrap($value);
 
         return $this;
     }
 
     public function validate(Closure $callback)
     {
-        $this->validators[] = $callback;
+        $this->listeners['validate'][] = $callback;
 
         return $this;
     }
 
     public function filterable(Closure $callback = null)
     {
-        $this->filterable = true;
-        $this->filter = $callback;
+        $this->filterable = $callback ?: true;
 
         return $this;
     }
 
-    protected function wrap($value)
+    public function notFilterable()
     {
-        if (! $value instanceof Closure) {
-            $value = function () use ($value) {
-                return $value;
-            };
-        }
+        $this->filterable = false;
 
-        return $value;
+        return $this;
     }
+
+    public function getName(): string
+    {
+        return $this->name;
+    }
+
+    public function getProperty()
+    {
+        return $this->property;
+    }
+
+    /**
+     * @return bool|Closure
+     */
+    public function getVisible()
+    {
+        return $this->visible;
+    }
+
+    public function getWritable()
+    {
+        return $this->writable;
+    }
+
+    public function getGetter()
+    {
+        return $this->getter;
+    }
+
+    public function getSetter()
+    {
+        return $this->setter;
+    }
+
+    public function getSaver()
+    {
+        return $this->saver;
+    }
+
+    public function getDefault()
+    {
+        return $this->default;
+    }
+
+    public function getFilterable()
+    {
+        return $this->filterable;
+    }
+
+
 }
diff --git a/src/Schema/HasMany.php b/src/Schema/HasMany.php
index c5d2956..32fb2ff 100644
--- a/src/Schema/HasMany.php
+++ b/src/Schema/HasMany.php
@@ -2,14 +2,12 @@
 
 namespace Tobyz\JsonApiServer\Schema;
 
-class HasMany extends Relationship
+final class HasMany extends Relationship
 {
-    public $includable = false;
-
     public function __construct(string $name)
     {
         parent::__construct($name);
 
-        $this->resource = $name;
+        $this->type($name);
     }
 }
diff --git a/src/Schema/HasOne.php b/src/Schema/HasOne.php
index 7624c05..b111c95 100644
--- a/src/Schema/HasOne.php
+++ b/src/Schema/HasOne.php
@@ -4,12 +4,12 @@ namespace Tobyz\JsonApiServer\Schema;
 
 use Doctrine\Common\Inflector\Inflector;
 
-class HasOne extends Relationship
+final class HasOne extends Relationship
 {
     public function __construct(string $name)
     {
         parent::__construct($name);
 
-        $this->resource = Inflector::pluralize($name);
+        $this->type(Inflector::pluralize($name));
     }
 }
diff --git a/src/Schema/Meta.php b/src/Schema/Meta.php
index 271944a..153fa3f 100644
--- a/src/Schema/Meta.php
+++ b/src/Schema/Meta.php
@@ -3,26 +3,26 @@
 namespace Tobyz\JsonApiServer\Schema;
 
 use Closure;
+use function Tobyz\JsonApiServer\wrap;
 
-class Meta
+final class Meta
 {
-    public $name;
-    public $value;
+    private $name;
+    private $value;
 
     public function __construct(string $name, $value)
     {
         $this->name = $name;
-        $this->value = $this->wrap($value);
+        $this->value = wrap($value);
     }
 
-    private function wrap($value)
+    public function getName(): string
     {
-        if (! $value instanceof Closure) {
-            $value = function () use ($value) {
-                return $value;
-            };
-        }
+        return $this->name;
+    }
 
-        return $value;
+    public function getValue(): Closure
+    {
+        return $this->value;
     }
 }
diff --git a/src/Schema/Relationship.php b/src/Schema/Relationship.php
index 2491c9b..0fc9625 100644
--- a/src/Schema/Relationship.php
+++ b/src/Schema/Relationship.php
@@ -3,57 +3,47 @@
 namespace Tobyz\JsonApiServer\Schema;
 
 use Closure;
-use Tobyz\JsonApiServer\Handler\Show;
+use function Tobyz\JsonApiServer\negate;
 
 abstract class Relationship extends Field
 {
-    public $location = 'relationships';
-    public $linkage;
-    public $hasLinks = true;
-    public $loadable = true;
-    public $loader;
-    public $included = false;
-    public $includable = true;
-    public $resource;
+    private $type;
+    private $linkage = false;
+    private $links = true;
+    private $loadable = true;
+    private $includable = false;
 
-    public function __construct(string $name)
+    public function type($type)
     {
-        parent::__construct($name);
-
-        $this->noLinkage();
-    }
-
-    public function resource($resource)
-    {
-        $this->resource = $resource;
+        $this->type = $type;
 
         return $this;
     }
 
-    public function linkageIf(Closure $condition)
+    public function polymorphic()
     {
-        $this->linkage = $condition;
+        $this->type = null;
 
         return $this;
     }
 
-    public function linkage()
+    public function linkage(Closure $condition = null)
     {
-        return $this->linkageIf(function () {
-            return true;
-        });
+        $this->linkage = $condition ?: true;
+
+        return $this;
     }
 
-    public function noLinkage()
+    public function noLinkage(Closure $condition = null)
     {
-        return $this->linkageIf(function () {
-            return false;
-        });
+        $this->linkage = $condition ? negate($condition) : false;
+
+        return $this;
     }
 
-    public function loadable()
+    public function loadable(Closure $callback = null)
     {
-        $this->loadable = true;
+        $this->loadable = $callback ?: true;
 
         return $this;
     }
@@ -65,13 +55,6 @@ abstract class Relationship extends Field
         return $this;
     }
 
-    public function load(Closure $callback)
-    {
-        $this->loader = $callback;
-
-        return $this;
-    }
-
     public function includable()
     {
         $this->includable = true;
@@ -86,10 +69,47 @@ abstract class Relationship extends Field
         return $this;
     }
 
-    public function noLinks()
+    public function getType()
     {
-        $this->hasLinks = false;
+        return $this->type;
+    }
+
+    public function links()
+    {
+        $this->links = true;
 
         return $this;
     }
+
+    public function noLinks()
+    {
+        $this->links = false;
+
+        return $this;
+    }
+
+    public function getLinkage()
+    {
+        return $this->linkage;
+    }
+
+    public function hasLinks(): bool
+    {
+        return $this->links;
+    }
+
+    public function getLoadable()
+    {
+        return $this->loadable;
+    }
+
+    public function isIncludable(): bool
+    {
+        return $this->includable;
+    }
+
+    public function getLocation(): string
+    {
+        return 'relationships';
+    }
 }
diff --git a/src/Schema/Type.php b/src/Schema/Type.php
new file mode 100644
index 0000000..e12eb0f
--- /dev/null
+++ b/src/Schema/Type.php
@@ -0,0 +1,282 @@
+<?php
+
+namespace Tobyz\JsonApiServer\Schema;
+
+use Closure;
+use function Tobyz\JsonApiServer\negate;
+use Tobyz\JsonApiServer\Schema\Concerns\HasListeners;
+
+final class Type
+{
+    use HasListeners;
+
+    private $fields = [];
+    private $meta = [];
+    private $paginate = 20;
+    private $limit = 50;
+    private $countable = true;
+    private $defaultSort;
+    private $scopes = [];
+    private $saver;
+    private $creatable = false;
+    private $create;
+    private $updatable = false;
+    private $deletable = false;
+    private $delete;
+
+    public function attribute(string $name): Attribute
+    {
+        return $this->field(Attribute::class, $name);
+    }
+
+    public function hasOne(string $name): HasOne
+    {
+        return $this->field(HasOne::class, $name);
+    }
+
+    public function hasMany(string $name): HasMany
+    {
+        return $this->field(HasMany::class, $name);
+    }
+
+    private function field(string $class, string $name)
+    {
+        if (! isset($this->fields[$name]) || ! $this->fields[$name] instanceof $class) {
+            $this->fields[$name] = new $class($name);
+        }
+
+        return $this->fields[$name];
+    }
+
+    public function removeField(string $name)
+    {
+        unset($this->fields[$name]);
+
+        return $this;
+    }
+
+    /**
+     * @return Field[]
+     */
+    public function getFields(): array
+    {
+        return $this->fields;
+    }
+
+    public function meta(string $name, $value)
+    {
+        return $this->meta[$name] = new Meta($name, $value);
+    }
+
+    public function removeMeta(string $name)
+    {
+        unset($this->meta[$name]);
+
+        return $this;
+    }
+
+    public function getMeta(): array
+    {
+        return $this->meta;
+    }
+
+    public function paginate(int $perPage)
+    {
+        $this->paginate = $perPage;
+    }
+
+    public function dontPaginate()
+    {
+        $this->paginate = null;
+    }
+
+    public function getPaginate(): int
+    {
+        return $this->paginate;
+    }
+
+    public function limit(int $limit)
+    {
+        $this->limit = $limit;
+    }
+
+    public function noLimit()
+    {
+        $this->limit = null;
+    }
+
+    public function getLimit(): int
+    {
+        return $this->limit;
+    }
+
+    public function countable()
+    {
+        $this->countable = true;
+    }
+
+    public function uncountable()
+    {
+        $this->countable = false;
+    }
+
+    public function isCountable(): bool
+    {
+        return $this->countable;
+    }
+
+    public function scope(Closure $callback)
+    {
+        $this->scopes[] = $callback;
+    }
+
+    public function getScopes(): array
+    {
+        return $this->scopes;
+    }
+
+    public function create(?Closure $callback)
+    {
+        $this->create = $callback;
+    }
+
+    public function getCreator()
+    {
+        return $this->create;
+    }
+
+    public function creatable(Closure $condition = null)
+    {
+        $this->creatable = $condition ?: true;
+
+        return $this;
+    }
+
+    public function notCreatable(Closure $condition = null)
+    {
+        $this->creatable = $condition ? negate($condition) : false;
+
+        return $this;
+    }
+
+    public function getCreatable()
+    {
+        return $this->creatable;
+    }
+
+    public function creating(Closure $callback)
+    {
+        $this->listeners['creating'][] = $callback;
+
+        return $this;
+    }
+
+    public function created(Closure $callback)
+    {
+        $this->listeners['created'][] = $callback;
+
+        return $this;
+    }
+
+    public function updatable(Closure $condition = null)
+    {
+        $this->updatable = $condition ?: true;
+
+        return $this;
+    }
+
+    public function notUpdatable(Closure $condition = null)
+    {
+        $this->updatable = $condition ? negate($condition) : false;
+
+        return $this;
+    }
+
+    public function getUpdatable()
+    {
+        return $this->updatable;
+    }
+
+    public function updating(Closure $callback)
+    {
+        $this->listeners['updating'][] = $callback;
+
+        return $this;
+    }
+
+    public function updated(Closure $callback)
+    {
+        $this->listeners['updated'][] = $callback;
+
+        return $this;
+    }
+
+    public function save(?Closure $callback)
+    {
+        $this->saver = $callback;
+
+        return $this;
+    }
+
+    public function getSaver()
+    {
+        return $this->saver;
+    }
+
+    public function deletable(Closure $condition = null)
+    {
+        $this->deletable = $condition ?: true;
+
+        return $this;
+    }
+
+    public function notDeletable(Closure $condition = null)
+    {
+        $this->deletable = $condition ? negate($condition) : false;
+
+        return $this;
+    }
+
+    public function getDeletable()
+    {
+        return $this->deletable;
+    }
+
+    public function delete(?Closure $callback)
+    {
+        $this->delete = $callback;
+
+        return $this;
+    }
+
+    public function getDelete()
+    {
+        return $this->delete;
+    }
+
+    public function deleting(Closure $callback)
+    {
+        $this->listeners['deleting'][] = $callback;
+
+        return $this;
+    }
+
+    public function deleted(Closure $callback)
+    {
+        $this->listeners['deleted'][] = $callback;
+
+        return $this;
+    }
+
+    public function defaultSort(?string $sort)
+    {
+        $this->defaultSort = $sort;
+
+        return $this;
+    }
+
+    public function getDefaultSort()
+    {
+        return $this->defaultSort;
+    }
+}
diff --git a/src/Serializer.php b/src/Serializer.php
index 5e69b18..dd2512d 100644
--- a/src/Serializer.php
+++ b/src/Serializer.php
@@ -4,9 +4,18 @@ namespace Tobyz\JsonApiServer;
 
 use DateTime;
 use DateTimeInterface;
-use JsonApiPhp\JsonApi;
+use JsonApiPhp\JsonApi as Structure;
+use JsonApiPhp\JsonApi\EmptyRelationship;
+use JsonApiPhp\JsonApi\Link\RelatedLink;
+use JsonApiPhp\JsonApi\Link\SelfLink;
+use JsonApiPhp\JsonApi\ResourceIdentifier;
+use JsonApiPhp\JsonApi\ResourceIdentifierCollection;
+use JsonApiPhp\JsonApi\ToMany;
+use JsonApiPhp\JsonApi\ToOne;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Tobyz\JsonApiServer\Adapter\AdapterInterface;
+use Tobyz\JsonApiServer\Schema\Attribute;
+use Tobyz\JsonApiServer\Schema\Relationship;
 
 class Serializer
 {
@@ -15,7 +24,7 @@ class Serializer
     protected $map = [];
     protected $primary = [];
 
-    public function __construct(Api $api, Request $request)
+    public function __construct(JsonApi $api, Request $request)
     {
         $this->api = $api;
         $this->request = $request;
@@ -43,7 +52,7 @@ class Serializer
 
         $resourceUrl = $this->api->getBaseUrl().'/'.$data['type'].'/'.$data['id'];
 
-        $fields = $schema->fields;
+        $fields = $schema->getFields();
 
         $queryParams = $this->request->getQueryParams();
 
@@ -60,7 +69,7 @@ class Serializer
                 continue;
             }
 
-            if (! ($field->isVisible)($this->request, $model)) {
+            if (! evaluate($field->getVisible(), [$model, $this->request])) {
                 continue;
             }
 
@@ -68,7 +77,7 @@ class Serializer
                 $value = $this->attribute($field, $model, $adapter);
             } elseif ($field instanceof Schema\Relationship) {
                 $isIncluded = isset($include[$name]);
-                $isLinkage = ($field->linkage)($this->request);
+                $isLinkage = evaluate($field->getLinkage(), [$this->request]);
 
                 if (! $isIncluded && ! $isLinkage) {
                     $value = $this->emptyRelationship($field, $resourceUrl);
@@ -82,12 +91,14 @@ class Serializer
             $data['fields'][$name] = $value;
         }
 
-        $data['links']['self'] = new JsonApi\Link\SelfLink($resourceUrl);
+        $data['links']['self'] = new SelfLink($resourceUrl);
 
-        ksort($schema->meta);
+        $metas = $schema->getMeta();
 
-        foreach ($schema->meta as $name => $meta) {
-            $data['meta'][$name] = new JsonApi\Meta($meta->name, ($meta->value)($this->request, $model));
+        ksort($metas);
+
+        foreach ($metas as $name => $meta) {
+            $data['meta'][$name] = new Structure\Meta($meta->name, ($meta->value)($this->request, $model));
         }
 
         $this->merge($data);
@@ -95,10 +106,10 @@ class Serializer
         return $data;
     }
 
-    private function attribute(Schema\Attribute $field, $model, AdapterInterface $adapter): JsonApi\Attribute
+    private function attribute(Attribute $field, $model, AdapterInterface $adapter): Structure\Attribute
     {
-        if ($field->getter) {
-            $value = ($field->getter)($this->request, $model);
+        if ($getter = $field->getGetter()) {
+            $value = $getter($model, $this->request);
         } else {
             $value = $adapter->getAttribute($model, $field);
         }
@@ -107,18 +118,18 @@ class Serializer
             $value = $value->format(DateTime::RFC3339);
         }
 
-        return new JsonApi\Attribute($field->name, $value);
+        return new Structure\Attribute($field->getName(), $value);
     }
 
     private function toOne(Schema\HasOne $field, $model, AdapterInterface $adapter, bool $isIncluded, bool $isLinkage, array $include, string $resourceUrl)
     {
         $links = $this->getRelationshipLinks($field, $resourceUrl);
 
-        $value = $isIncluded ? ($field->getter ? ($field->getter)($this->request, $model) : $adapter->getHasOne($model, $field)) : ($isLinkage && $field->loadable ? $adapter->getHasOneId($model, $field) : null);
+        $value = $isIncluded ? (($getter = $field->getGetter()) ? $getter($model, $this->request) : $adapter->getHasOne($model, $field)) : ($isLinkage && $field->getLoadable() ? $adapter->getHasOneId($model, $field) : null);
 
         if (! $value) {
-            return new JsonApi\ToNull(
-                $field->name,
+            return new Structure\ToNull(
+                $field->getName(),
                 ...$links
             );
         }
@@ -130,8 +141,8 @@ class Serializer
         }
 
 
-        return new JsonApi\ToOne(
-            $field->name,
+        return new ToOne(
+            $field->getName(),
             $identifier,
             ...$links
         );
@@ -139,8 +150,8 @@ class Serializer
 
     private function toMany(Schema\HasMany $field, $model, AdapterInterface $adapter, bool $isIncluded, bool $isLinkage, array $include, string $resourceUrl)
     {
-        if ($field->getter) {
-            $value = ($field->getter)($this->request, $model);
+        if ($getter = $field->getGetter()) {
+            $value = $getter($model, $this->request);
         } else {
             $value = ($isLinkage || $isIncluded) ? $adapter->getHasMany($model, $field) : null;
         }
@@ -157,36 +168,36 @@ class Serializer
             }
         }
 
-        return new JsonApi\ToMany(
-            $field->name,
-            new JsonApi\ResourceIdentifierCollection(...$identifiers),
+        return new ToMany(
+            $field->getName(),
+            new ResourceIdentifierCollection(...$identifiers),
             ...$this->getRelationshipLinks($field, $resourceUrl)
         );
     }
 
-    private function emptyRelationship(Schema\Relationship $field, string $resourceUrl): JsonApi\EmptyRelationship
+    private function emptyRelationship(Relationship $field, string $resourceUrl): EmptyRelationship
     {
-        return new JsonApi\EmptyRelationship(
-            $field->name,
+        return new EmptyRelationship(
+            $field->getName(),
             ...$this->getRelationshipLinks($field, $resourceUrl)
         );
     }
 
-    private function getRelationshipLinks(Schema\Relationship $field, string $resourceUrl): array
+    private function getRelationshipLinks(Relationship $field, string $resourceUrl): array
     {
-        if (! $field->hasLinks) {
+        if (! $field->hasLinks()) {
             return [];
         }
 
         return [
-            new JsonApi\Link\SelfLink($resourceUrl.'/relationships/'.$field->name),
-            new JsonApi\Link\RelatedLink($resourceUrl.'/'.$field->name)
+            new SelfLink($resourceUrl.'/relationships/'.$field->getName()),
+            new RelatedLink($resourceUrl.'/'.$field->getName())
         ];
     }
 
-    private function addRelated(Schema\Relationship $field, $model, array $include): JsonApi\ResourceIdentifier
+    private function addRelated(Relationship $field, $model, array $include): ResourceIdentifier
     {
-        $relatedResource = $field->resource ? $this->api->getResource($field->resource) : $this->resourceForModel($model);
+        $relatedResource = $field->getType() ? $this->api->getResource($field->getType()) : $this->resourceForModel($model);
 
         return $this->resourceIdentifier(
             $this->addToMap($relatedResource, $model, $include)
@@ -238,9 +249,9 @@ class Serializer
         }, $items);
     }
 
-    private function resourceObject(array $data): JsonApi\ResourceObject
+    private function resourceObject(array $data): Structure\ResourceObject
     {
-        return new JsonApi\ResourceObject(
+        return new Structure\ResourceObject(
             $data['type'],
             $data['id'],
             ...array_values($data['fields']),
@@ -249,9 +260,9 @@ class Serializer
         );
     }
 
-    private function resourceIdentifier(array $data): JsonApi\ResourceIdentifier
+    private function resourceIdentifier(array $data): Structure\ResourceIdentifier
     {
-        return new JsonApi\ResourceIdentifier(
+        return new Structure\ResourceIdentifier(
             $data['type'],
             $data['id']
         );
diff --git a/src/StatusProviderInterface.php b/src/StatusProviderInterface.php
deleted file mode 100644
index f38bbe6..0000000
--- a/src/StatusProviderInterface.php
+++ /dev/null
@@ -1,8 +0,0 @@
-<?php
-
-namespace Tobyz\JsonApiServer;
-
-interface StatusProviderInterface
-{
-    public function getJsonApiStatus(): array;
-}
diff --git a/src/functions.php b/src/functions.php
new file mode 100644
index 0000000..87446bf
--- /dev/null
+++ b/src/functions.php
@@ -0,0 +1,64 @@
+<?php
+
+namespace Tobyz\JsonApiServer;
+
+use Closure;
+use Tobyz\JsonApiServer\Schema\Field;
+
+function negate(Closure $condition)
+{
+    return function (...$args) use ($condition) {
+        return ! $condition(...$args);
+    };
+}
+
+function wrap($value)
+{
+    if (! $value instanceof Closure) {
+        $value = function () use ($value) {
+            return $value;
+        };
+    }
+
+    return $value;
+}
+
+function evaluate($condition, array $params)
+{
+    return $condition === true || ($condition instanceof Closure && $condition(...$params));
+}
+
+function run_callbacks(array $callbacks, array $params)
+{
+    foreach ($callbacks as $callback) {
+        $callback(...$params);
+    }
+}
+
+function has_value(array $data, Field $field)
+{
+    return isset($data[$field->getLocation()][$field->getName()]);
+}
+
+function &get_value(array $data, Field $field)
+{
+    return $data[$field->getLocation()][$field->getName()];
+}
+
+function set_value(array &$data, Field $field, $value)
+{
+    $data[$field->getLocation()][$field->getName()] = $value;
+}
+
+function array_set(array $array, $key, $value)
+{
+    $keys = explode('.', $key);
+
+    while (count($keys) > 1) {
+        $array = &$array[array_shift($keys)];
+    }
+
+    $array[array_shift($keys)] = $value;
+
+    return $array;
+}
diff --git a/tests/AbstractTestCase.php b/tests/AbstractTestCase.php
index ef13fcc..a4d4054 100644
--- a/tests/AbstractTestCase.php
+++ b/tests/AbstractTestCase.php
@@ -11,19 +11,19 @@
 
 namespace Tobyz\Tests\JsonApiServer;
 
+use DMS\PHPUnitExtensions\ArraySubset\ArraySubsetAsserts;
 use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\ResponseInterface;
 use Zend\Diactoros\ServerRequest;
 use Zend\Diactoros\Uri;
 
 abstract class AbstractTestCase extends TestCase
 {
-    public static function assertEncodesTo(string $expected, $obj, string $message = '')
+    use ArraySubsetAsserts;
+
+    protected function assertJsonApiDocumentSubset($subset, string $body, bool $checkForObjectIdentity = false, string $message = ''): void
     {
-        self::assertEquals(
-            json_decode($expected),
-            json_decode(json_encode($obj, JSON_UNESCAPED_SLASHES)),
-            $message
-        );
+        static::assertArraySubset($subset, json_decode($body, true), $checkForObjectIdentity, $message);
     }
 
     protected function buildRequest(string $method, string $uri): ServerRequest
diff --git a/tests/CreateTest.php b/tests/CreateTest.old.php
similarity index 88%
rename from tests/CreateTest.php
rename to tests/CreateTest.old.php
index 6fe6fd4..007bbeb 100644
--- a/tests/CreateTest.php
+++ b/tests/CreateTest.old.php
@@ -11,11 +11,11 @@
 
 namespace Tobyz\Tests\JsonApiServer;
 
-use Tobyz\JsonApiServer\Api;
+use Tobyz\JsonApiServer\JsonApi;
 use Tobyz\JsonApiServer\Exception\BadRequestException;
 use Tobyz\JsonApiServer\Exception\ForbiddenException;
 use Tobyz\JsonApiServer\Serializer;
-use Tobyz\JsonApiServer\Schema\Builder;
+use Tobyz\JsonApiServer\Schema\Type;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use JsonApiPhp\JsonApi;
 use Zend\Diactoros\ServerRequest;
@@ -25,9 +25,9 @@ class CreateTest extends AbstractTestCase
 {
     public function testResourceNotCreatableByDefault()
     {
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', new MockAdapter(), function (Builder $schema) {
+        $api->resource('users', new MockAdapter(), function (Type $schema) {
             //
         });
 
@@ -41,9 +41,9 @@ class CreateTest extends AbstractTestCase
 
     public function testCreateResourceValidatesBody()
     {
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', new MockAdapter(), function (Builder $schema) {
+        $api->resource('users', new MockAdapter(), function (Type $schema) {
             $schema->creatable();
         });
 
@@ -56,9 +56,9 @@ class CreateTest extends AbstractTestCase
 
     public function testCreateResource()
     {
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $adapter = new MockAdapter(), function (Builder $schema) {
+        $api->resource('users', $adapter = new MockAdapter(), function (Type $schema) {
             $schema->creatable();
 
             $schema->attribute('name')->writable();
@@ -110,9 +110,9 @@ class CreateTest extends AbstractTestCase
                 ]
             ]);
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $adapter = new MockAdapter(), function (Builder $schema) use ($adapter, $request) {
+        $api->resource('users', $adapter = new MockAdapter(), function (Type $schema) use ($adapter, $request) {
             $schema->creatable();
 
             $schema->attribute('writable1')->writable();
@@ -148,9 +148,9 @@ class CreateTest extends AbstractTestCase
                 ]
             ]);
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $adapter = new MockAdapter(), function (Builder $schema) use ($adapter, $request) {
+        $api->resource('users', $adapter = new MockAdapter(), function (Type $schema) use ($adapter, $request) {
             $schema->creatable();
 
             $schema->attribute('readonly')->readonly();
@@ -175,9 +175,9 @@ class CreateTest extends AbstractTestCase
                 ]
             ]);
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $adapter = new MockAdapter(), function (Builder $schema) use ($request) {
+        $api->resource('users', $adapter = new MockAdapter(), function (Type $schema) use ($request) {
             $schema->creatable();
 
             $schema->attribute('attribute1')->default('defaultValue');
diff --git a/tests/DeleteTest.php b/tests/DeleteTest.old.php
similarity index 80%
rename from tests/DeleteTest.php
rename to tests/DeleteTest.old.php
index 8ef4351..3f1574d 100644
--- a/tests/DeleteTest.php
+++ b/tests/DeleteTest.old.php
@@ -11,11 +11,11 @@
 
 namespace Tobyz\Tests\JsonApiServer;
 
-use Tobyz\JsonApiServer\Api;
+use Tobyz\JsonApiServer\JsonApi;
 use Tobyz\JsonApiServer\Exception\BadRequestException;
 use Tobyz\JsonApiServer\Exception\ForbiddenException;
 use Tobyz\JsonApiServer\Serializer;
-use Tobyz\JsonApiServer\Schema\Builder;
+use Tobyz\JsonApiServer\Schema\Type;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use JsonApiPhp\JsonApi;
 use Zend\Diactoros\ServerRequest;
@@ -25,9 +25,9 @@ class DeleteTest extends AbstractTestCase
 {
     public function testResourceNotDeletableByDefault()
     {
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', new MockAdapter(), function (Builder $schema) {
+        $api->resource('users', new MockAdapter(), function (Type $schema) {
             //
         });
 
@@ -45,9 +45,9 @@ class DeleteTest extends AbstractTestCase
             '1' => $user = (object)['id' => '1']
         ]);
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $usersAdapter, function (Builder $schema) {
+        $api->resource('users', $usersAdapter, function (Type $schema) {
             $schema->deletable();
         });
 
diff --git a/tests/MockAdapter.php b/tests/MockAdapter.php
index d687886..4500bfa 100644
--- a/tests/MockAdapter.php
+++ b/tests/MockAdapter.php
@@ -13,6 +13,7 @@ class MockAdapter implements AdapterInterface
 {
     public $models = [];
     public $createdModel;
+    public $query;
     private $type;
 
     public function __construct(array $models = [], string $type = null)
@@ -28,10 +29,10 @@ class MockAdapter implements AdapterInterface
 
     public function query()
     {
-        return (object) [];
+        return $this->query = (object) [];
     }
 
-    public function find($query, $id)
+    public function find($query, string $id)
     {
         return $this->models[$id] ?? (object) ['id' => $id];
     }
@@ -61,17 +62,17 @@ class MockAdapter implements AdapterInterface
         return $model->{$this->getProperty($relationship)} ?? [];
     }
 
-    public function applyAttribute($model, Attribute $attribute, $value)
+    public function setAttribute($model, Attribute $attribute, $value): void
     {
         $model->{$this->getProperty($attribute)} = $value;
     }
 
-    public function applyHasOne($model, HasOne $relationship, $related)
+    public function setHasOne($model, HasOne $relationship, $related): void
     {
         $model->{$this->getProperty($relationship)} = $related;
     }
 
-    public function save($model)
+    public function save($model): void
     {
         $model->saveWasCalled = true;
 
@@ -80,59 +81,54 @@ class MockAdapter implements AdapterInterface
         }
     }
 
-    public function saveHasMany($model, HasMany $relationship, array $related)
+    public function saveHasMany($model, HasMany $relationship, array $related): void
     {
         $model->saveHasManyWasCalled = true;
     }
 
-    public function delete($model)
+    public function delete($model): void
     {
         $model->deleteWasCalled = true;
     }
 
-    public function filterByIds($query, array $ids)
+    public function filterByIds($query, array $ids): void
     {
-        $query->filters[] = ['ids', $ids];
+        $query->filter[] = ['ids', $ids];
     }
 
-    public function filterByAttribute($query, Attribute $attribute, $value)
+    public function filterByAttribute($query, Attribute $attribute, $value): void
     {
-        $query->filters[] = [$attribute, $value];
+        $query->filter[] = [$attribute, $value];
     }
 
-    public function filterByHasOne($query, HasOne $relationship, array $ids)
+    public function filterByHasOne($query, HasOne $relationship, array $ids): void
     {
-        $query->filters[] = [$relationship, $ids];
+        $query->filter[] = [$relationship, $ids];
     }
 
-    public function filterByHasMany($query, HasMany $relationship, array $ids)
+    public function filterByHasMany($query, HasMany $relationship, array $ids): void
     {
-        $query->filters[] = [$relationship, $ids];
+        $query->filter[] = [$relationship, $ids];
     }
 
-    public function sortByAttribute($query, Attribute $attribute, string $direction)
+    public function sortByAttribute($query, Attribute $attribute, string $direction): void
     {
         $query->sort[] = [$attribute, $direction];
     }
 
-    public function paginate($query, int $limit, int $offset)
+    public function paginate($query, int $limit, int $offset): void
     {
         $query->paginate[] = [$limit, $offset];
     }
 
-    public function include($query, array $relationships)
-    {
-        $query->include[] = $relationships;
-    }
-
-    public function load(array $models, array $relationships)
+    public function load(array $models, array $relationships): void
     {
         foreach ($models as $model) {
             $model->load[] = $relationships;
         }
     }
 
-    public function loadIds(array $models, Relationship $relationship)
+    public function loadIds(array $models, Relationship $relationship): void
     {
         foreach ($models as $model) {
             $model->loadIds[] = $relationship;
@@ -141,11 +137,34 @@ class MockAdapter implements AdapterInterface
 
     private function getProperty(Field $field)
     {
-        return $field->property ?: $field->name;
+        return $field->getProperty() ?: $field->getName();
     }
 
-    public function handles($model)
+    public function represents($model): bool
     {
         return isset($model['type']) && $model['type'] === $this->type;
     }
+
+    /**
+     * Get the number of results from the query.
+     *
+     * @param $query
+     * @return int
+     */
+    public function count($query): int
+    {
+        return count($this->models);
+    }
+
+    /**
+     * Get the ID of the related resource for a has-one relationship.
+     *
+     * @param $model
+     * @param HasOne $relationship
+     * @return mixed|null
+     */
+    public function getHasOneId($model, HasOne $relationship): ?string
+    {
+        // TODO: Implement getHasOneId() method.
+    }
 }
diff --git a/tests/ShowTest.php b/tests/ShowTest.old.php
similarity index 88%
rename from tests/ShowTest.php
rename to tests/ShowTest.old.php
index 32e0b0d..46a4161 100644
--- a/tests/ShowTest.php
+++ b/tests/ShowTest.old.php
@@ -11,21 +11,17 @@
 
 namespace Tobyz\Tests\JsonApiServer;
 
-use Tobyz\JsonApiServer\Api;
+use Tobyz\JsonApiServer\JsonApi;
 use Tobyz\JsonApiServer\Exception\BadRequestException;
-use Tobyz\JsonApiServer\Serializer;
-use Tobyz\JsonApiServer\Schema\Builder;
+use Tobyz\JsonApiServer\Schema\Type;
 use Psr\Http\Message\ServerRequestInterface as Request;
-use JsonApiPhp\JsonApi;
-use Zend\Diactoros\ServerRequest;
-use Zend\Diactoros\Uri;
 
 class ShowTest extends AbstractTestCase
 {
-    public function testResourceWithNoFields()
+    public function test_resource_with_no_fields()
     {
-        $api = new Api('http://example.com');
-        $api->resource('users', new MockAdapter(), function (Builder $schema) {
+        $api = new JsonApi('http://example.com');
+        $api->resource('users', new MockAdapter(), function (Type $schema) {
             // no fields
         });
 
@@ -35,17 +31,19 @@ class ShowTest extends AbstractTestCase
         $this->assertEquals($response->getStatusCode(), 200);
         $this->assertEquals(
             [
-                'type' => 'users',
-                'id' => '1',
-                'links' => [
-                    'self' => 'http://example.com/users/1'
+                'data' => [
+                    'type' => 'users',
+                    'id' => '1',
+                    'links' => [
+                        'self' => 'http://example.com/users/1'
+                    ]
                 ]
             ],
-            json_decode($response->getBody(), true)['data']
+            json_decode($response->getBody(), true)
         );
     }
 
-    public function testAttributes()
+    public function test_attributes()
     {
         $adapter = new MockAdapter([
             '1' => (object) [
@@ -58,9 +56,9 @@ class ShowTest extends AbstractTestCase
 
         $request = $this->buildRequest('GET', '/users/1');
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $adapter, function (Builder $schema) {
+        $api->resource('users', $adapter, function (Type $schema) {
             $schema->attribute('attribute1');
             $schema->attribute('attribute2', 'property2');
             $schema->attribute('attribute3')->property('property3');
@@ -88,9 +86,9 @@ class ShowTest extends AbstractTestCase
 
         $request = $this->buildRequest('GET', '/users/1');
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $adapter, function (Builder $schema) use ($model, $request) {
+        $api->resource('users', $adapter, function (Type $schema) use ($model, $request) {
             $schema->attribute('attribute1')
                 ->get(function ($arg1, $arg2) use ($model, $request) {
                     $this->assertInstanceOf(Request::class, $arg1);
@@ -120,8 +118,8 @@ class ShowTest extends AbstractTestCase
 
         $request = $this->buildRequest('GET', '/users/1');
 
-        $api = new Api('http://example.com');
-        $api->resource('users', $adapter, function (Builder $schema) use ($model, $request) {
+        $api = new JsonApi('http://example.com');
+        $api->resource('users', $adapter, function (Type $schema) use ($model, $request) {
             $schema->attribute('visible1');
 
             $schema->attribute('visible2')->visible();
@@ -183,19 +181,19 @@ class ShowTest extends AbstractTestCase
         $request = $this->buildRequest('GET', '/users/1')
             ->withQueryParams(['include' => 'phone,phone2,phone3']);
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $usersAdapter, function (Builder $schema) {
+        $api->resource('users', $usersAdapter, function (Type $schema) {
             $schema->hasOne('phone');
 
             $schema->hasOne('phone2', 'phones', 'property2');
 
             $schema->hasOne('phone3')
-                ->resource('phones')
+                ->type('phones')
                 ->property('property3');
         });
 
-        $api->resource('phones', $phonesAdapter, function (Builder $schema) {
+        $api->resource('phones', $phonesAdapter, function (Type $schema) {
             $schema->attribute('number');
         });
 
@@ -267,15 +265,15 @@ class ShowTest extends AbstractTestCase
         $request = $this->buildRequest('GET', '/users/1')
             ->withQueryParams(['include' => 'phone2']);
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $usersAdapter, function (Builder $schema) {
+        $api->resource('users', $usersAdapter, function (Type $schema) {
             $schema->hasOne('phone');
 
             $schema->hasOne('phone2', 'phones', 'property2');
         });
 
-        $api->resource('phones', $phonesAdapter, function (Builder $schema) {
+        $api->resource('phones', $phonesAdapter, function (Type $schema) {
             $schema->attribute('number');
         });
 
@@ -338,9 +336,9 @@ class ShowTest extends AbstractTestCase
 
     public function testHasManyRelationshipNotIncludableByDefault()
     {
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', new MockAdapter(), function (Builder $schema) {
+        $api->resource('users', new MockAdapter(), function (Type $schema) {
             $schema->hasMany('groups');
         });
 
@@ -365,9 +363,9 @@ class ShowTest extends AbstractTestCase
             ]
         ]);
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
-        $api->resource('users', $usersAdapter, function (Builder $schema) {
+        $api->resource('users', $usersAdapter, function (Type $schema) {
             $schema->hasMany('groups');
         });
 
@@ -400,11 +398,11 @@ class ShowTest extends AbstractTestCase
             ]
         ]);
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
         $relationships = [];
 
-        $api->resource('users', $usersAdapter, function (Builder $schema) use (&$relationships) {
+        $api->resource('users', $usersAdapter, function (Type $schema) use (&$relationships) {
             $relationships[] = $schema->hasMany('groups1', 'groups', 'property1')
                 ->includable();
 
@@ -412,7 +410,7 @@ class ShowTest extends AbstractTestCase
                 ->includable();
         });
 
-        $api->resource('groups', $groupsAdapter, function (Builder $schema) {
+        $api->resource('groups', $groupsAdapter, function (Type $schema) {
             $schema->attribute('name');
         });
 
@@ -519,19 +517,19 @@ class ShowTest extends AbstractTestCase
             '1' => $post = (object) ['id' => '1', 'user' => $user]
         ]);
 
-        $api = new Api('http://example.com');
+        $api = new JsonApi('http://example.com');
 
         $relationships = [];
 
-        $api->resource('posts', $postsAdapter, function (Builder $schema) use (&$relationships) {
+        $api->resource('posts', $postsAdapter, function (Type $schema) use (&$relationships) {
             $relationships[] = $schema->hasOne('user');
         });
 
-        $api->resource('users', $usersAdapter, function (Builder $schema) use (&$relationships) {
+        $api->resource('users', $usersAdapter, function (Type $schema) use (&$relationships) {
             $relationships[] = $schema->hasMany('groups')->includable();
         });
 
-        $api->resource('groups', $groupsAdapter, function (Builder $schema) {
+        $api->resource('groups', $groupsAdapter, function (Type $schema) {
             $schema->attribute('name');
         });
 
diff --git a/tests/feature/AttributeFilterableTest.php b/tests/feature/AttributeFilterableTest.php
new file mode 100644
index 0000000..0daa2b7
--- /dev/null
+++ b/tests/feature/AttributeFilterableTest.php
@@ -0,0 +1,107 @@
+<?php
+
+/*
+ * This file is part of tobyz/json-api-server.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Tobyz\Tests\JsonApiServer\feature;
+
+use Psr\Http\Message\ServerRequestInterface;
+use Tobyz\JsonApiServer\Exception\BadRequestException;
+use Tobyz\JsonApiServer\JsonApi;
+use Tobyz\JsonApiServer\Schema\Type;
+use Tobyz\Tests\JsonApiServer\AbstractTestCase;
+use Tobyz\Tests\JsonApiServer\MockAdapter;
+
+class AttributeFilterableTest extends AbstractTestCase
+{
+    /**
+     * @var JsonApi
+     */
+    private $api;
+
+    /**
+     * @var MockAdapter
+     */
+    private $adapter;
+
+    public function setUp(): void
+    {
+        $this->api = new JsonApi('http://example.com');
+
+        $this->adapter = new MockAdapter();
+    }
+
+    public function test_attributes_are_not_filterable_by_default()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->attribute('field');
+        });
+
+        $this->expectException(BadRequestException::class);
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users')
+                ->withQueryParams(['filter' => ['field' => 'Toby']])
+        );
+    }
+
+    public function test_attributes_can_be_filterable()
+    {
+        $attribute = null;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$attribute) {
+            $attribute = $type->attribute('name')->filterable();
+        });
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users')
+                ->withQueryParams(['filter' => ['name' => 'Toby']])
+        );
+
+        $this->assertContains([$attribute, 'Toby'], $this->adapter->query->filter);
+    }
+
+    public function test_attributes_can_be_filterable_with_custom_logic()
+    {
+        $called = false;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->attribute('name')
+                ->filterable(function ($query, $value, $request) use (&$called) {
+                    $this->assertSame($this->adapter->query, $query);
+                    $this->assertEquals('Toby', $value);
+                    $this->assertInstanceOf(ServerRequestInterface::class, $request);
+
+                    $called = true;
+                });
+        });
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users')
+                ->withQueryParams(['filter' => ['name' => 'Toby']])
+        );
+
+        $this->assertTrue($called);
+        $this->assertTrue(empty($this->adapter->query->filter));
+    }
+
+    public function test_attributes_can_be_explicitly_not_filterable()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->attribute('name')->notFilterable();
+        });
+
+        $this->expectException(BadRequestException::class);
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users')
+                ->withQueryParams(['filter' => ['name' => 'Toby']])
+        );
+    }
+}
diff --git a/tests/feature/AttributeSortableTest.php b/tests/feature/AttributeSortableTest.php
new file mode 100644
index 0000000..3bd290a
--- /dev/null
+++ b/tests/feature/AttributeSortableTest.php
@@ -0,0 +1,107 @@
+<?php
+
+/*
+ * This file is part of tobyz/json-api-server.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Tobyz\Tests\JsonApiServer\feature;
+
+use Psr\Http\Message\ServerRequestInterface;
+use Tobyz\JsonApiServer\Exception\BadRequestException;
+use Tobyz\JsonApiServer\JsonApi;
+use Tobyz\JsonApiServer\Schema\Type;
+use Tobyz\Tests\JsonApiServer\AbstractTestCase;
+use Tobyz\Tests\JsonApiServer\MockAdapter;
+
+class AttributeSortableTest extends AbstractTestCase
+{
+    /**
+     * @var JsonApi
+     */
+    private $api;
+
+    /**
+     * @var MockAdapter
+     */
+    private $adapter;
+
+    public function setUp(): void
+    {
+        $this->api = new JsonApi('http://example.com');
+
+        $this->adapter = new MockAdapter();
+    }
+
+    public function test_attributes_can_be_sortable()
+    {
+        $attribute = null;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$attribute) {
+            $attribute = $type->attribute('name')->sortable();
+        });
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users')
+                ->withQueryParams(['sort' => 'name'])
+        );
+
+        $this->assertContains([$attribute, 'asc'], $this->adapter->query->sort);
+    }
+
+    public function test_attributes_can_be_sortable_with_custom_logic()
+    {
+        $called = false;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->attribute('name')
+                ->sortable(function ($query, $direction, $request) use (&$called) {
+                    $this->assertSame($this->adapter->query, $query);
+                    $this->assertEquals('asc', $direction);
+                    $this->assertInstanceOf(ServerRequestInterface::class, $request);
+
+                    $called = true;
+                });
+        });
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users')
+                ->withQueryParams(['sort' => 'name'])
+        );
+
+        $this->assertTrue($called);
+        $this->assertTrue(empty($this->adapter->query->sort));
+    }
+
+    public function test_attributes_are_not_sortable_by_default()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->attribute('name');
+        });
+
+        $this->expectException(BadRequestException::class);
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users')
+                ->withQueryParams(['sort' => 'name'])
+        );
+    }
+
+    public function test_attributes_can_be_explicitly_not_sortable()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->attribute('name')->notSortable();
+        });
+
+        $this->expectException(BadRequestException::class);
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users')
+                ->withQueryParams(['sort' => 'name'])
+        );
+    }
+}
diff --git a/tests/feature/AttributeTest.php b/tests/feature/AttributeTest.php
new file mode 100644
index 0000000..a3b21bc
--- /dev/null
+++ b/tests/feature/AttributeTest.php
@@ -0,0 +1,393 @@
+<?php
+
+/*
+ * This file is part of tobyz/json-api-server.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Tobyz\Tests\JsonApiServer\feature;
+
+use JsonApiPhp\JsonApi\ErrorDocument;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Tobyz\JsonApiServer\ErrorProviderInterface;
+use Tobyz\JsonApiServer\Exception\UnprocessableEntityException;
+use Tobyz\JsonApiServer\JsonApi;
+use Tobyz\JsonApiServer\Schema\Attribute;
+use Tobyz\JsonApiServer\Schema\Type;
+use Tobyz\Tests\JsonApiServer\AbstractTestCase;
+use Tobyz\Tests\JsonApiServer\MockAdapter;
+
+class AttributeTest extends AbstractTestCase
+{
+    /**
+     * @var JsonApi
+     */
+    private $api;
+
+    /**
+     * @var MockAdapter
+     */
+    private $adapter;
+
+    public function setUp(): void
+    {
+        $this->api = new JsonApi('http://example.com');
+
+        $this->adapter = new MockAdapter([
+            '1' => (object) ['id' => '1', 'name' => 'Toby', 'color' => 'yellow'],
+            '2' => (object) ['id' => '2', 'name' => 'Franz', 'color' => 'blue'],
+        ]);
+    }
+
+    public function test_multiple_attributes()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->attribute('name');
+            $type->attribute('color');
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $this->assertJsonApiDocumentSubset([
+            'data' => [
+                'attributes' => [
+                    'name' => 'Toby',
+                    'color' => 'yellow',
+                ],
+            ]
+        ], $response->getBody());
+    }
+
+    public function test_attributes_can_specify_a_property()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->attribute('name')
+                ->property('color');
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $this->assertJsonApiDocumentSubset([
+            'data' => [
+                'attributes' => [
+                    'name' => 'yellow',
+                ],
+            ]
+        ], $response->getBody());
+    }
+
+    public function test_attributes_can_have_getters()
+    {
+        $called = false;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->attribute('name')
+                ->get('Toby');
+
+            $type->attribute('color')
+                ->get(function ($model, $request) use (&$called) {
+                    $called = true;
+
+                    $this->assertSame($this->adapter->models['1'], $model);
+                    $this->assertInstanceOf(RequestInterface::class, $request);
+
+                    return 'yellow';
+                });
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $this->assertTrue($called);
+
+        $this->assertJsonApiDocumentSubset([
+            'data' => [
+                'attributes' => [
+                    'name' => 'Toby',
+                    'color' => 'yellow',
+                ],
+            ]
+        ], $response->getBody());
+    }
+
+    public function test_attribute_setter_receives_correct_parameters()
+    {
+        $called = false;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->updatable();
+            $type->attribute('writable')
+                ->writable()
+                ->set(function ($model, $value, $request) use (&$called) {
+                    $this->assertSame($this->adapter->models['1'], $model);
+                    $this->assertEquals('value', $value);
+                    $this->assertInstanceOf(RequestInterface::class, $request);
+
+                    $called = true;
+                });
+        });
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertTrue($called);
+    }
+
+    public function test_attribute_setter_precludes_adapter_action()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->updatable();
+            $type->attribute('writable')
+                ->writable()
+                ->set(function () {});
+        });
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertTrue(empty($this->adapter->models['1']->writable));
+    }
+
+    public function test_attribute_saver_receives_correct_parameters()
+    {
+        $called = false;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->updatable();
+            $type->attribute('writable')
+                ->writable()
+                ->save(function ($model, $value, $request) use (&$called) {
+                    $this->assertSame($this->adapter->models['1'], $model);
+                    $this->assertEquals('value', $value);
+                    $this->assertInstanceOf(RequestInterface::class, $request);
+
+                    $called = true;
+                });
+        });
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertTrue($called);
+    }
+
+    public function test_attribute_saver_precludes_adapter_action()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->updatable();
+            $type->attribute('writable')
+                ->writable()
+                ->save(function () {});
+        });
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertTrue(empty($this->adapter->models['1']->writable));
+    }
+
+    public function test_attributes_can_run_callback_after_being_saved()
+    {
+        $called = false;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->updatable();
+            $type->attribute('writable')
+                ->writable()
+                ->saved(function ($model, $value, $request) use (&$called) {
+                    $this->assertTrue($this->adapter->models['1']->saveWasCalled);
+                    $this->assertSame($this->adapter->models['1'], $model);
+                    $this->assertEquals('value', $value);
+                    $this->assertInstanceOf(RequestInterface::class, $request);
+
+                    $called = true;
+                });
+        });
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertTrue($called);
+    }
+
+    public function test_attributes_can_have_default_values()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->creatable();
+
+            $type->attribute('name')
+                ->default('Toby');
+
+            $type->attribute('color')
+                ->default(function () {
+                    return 'yellow';
+                });
+        });
+
+        $this->api->handle(
+            $this->buildRequest('POST', '/users')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                    ]
+                ])
+        );
+
+        $this->assertEquals('Toby', $this->adapter->createdModel->name);
+        $this->assertEquals('yellow', $this->adapter->createdModel->color);
+    }
+
+    public function test_attribute_default_callback_receives_correct_parameters()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->creatable();
+            $type->attribute('attribute')
+                ->default(function ($request) {
+                    $this->assertInstanceOf(RequestInterface::class, $request);
+                });
+        });
+
+        $this->api->handle(
+            $this->buildRequest('POST', '/users')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                    ]
+                ])
+        );
+    }
+
+    public function test_attribute_values_from_request_override_default_values()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->creatable();
+            $type->attribute('name')
+                ->writable()
+                ->default('Toby');
+        });
+
+        $this->api->handle(
+            $this->buildRequest('POST', '/users')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'attributes' => [
+                            'name' => 'Franz',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertEquals('Franz', $this->adapter->createdModel->name);
+    }
+
+    public function test_attributes_can_be_validated()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->creatable();
+
+            $type->attribute('name')
+                ->writable()
+                ->validate(function ($fail, $value, $model, $request, $field) {
+                    $this->assertEquals('Toby', $value);
+                    $this->assertSame($this->adapter->createdModel, $model);
+                    $this->assertInstanceOf(ServerRequestInterface::class, $request);
+                    $this->assertInstanceOf(Attribute::class, $field);
+
+                    $fail('detail');
+                });
+        });
+
+        $this->expectException(UnprocessableEntityException::class);
+
+        try {
+            $this->api->handle(
+                $this->buildRequest('POST', '/users')
+                    ->withParsedBody([
+                        'data' => [
+                            'type' => 'users',
+                            'attributes' => [
+                                'name' => 'Toby',
+                            ]
+                        ]
+                    ])
+            );
+        } catch (ErrorProviderInterface $e) {
+            $document = new ErrorDocument(...$e->getJsonApiErrors());
+
+            $this->assertArraySubset([
+                'errors' => [
+                    [
+                        'status' => '422',
+                        'source' => [
+                            'pointer' => '/data/attributes/name'
+                        ],
+                        'detail' => 'detail'
+                    ]
+                ]
+            ], json_decode(json_encode($document), true));
+
+            throw $e;
+        }
+    }
+}
diff --git a/tests/feature/AttributeWritableTest.php b/tests/feature/AttributeWritableTest.php
new file mode 100644
index 0000000..371ebf7
--- /dev/null
+++ b/tests/feature/AttributeWritableTest.php
@@ -0,0 +1,274 @@
+<?php
+
+/*
+ * This file is part of tobyz/json-api-server.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Tobyz\Tests\JsonApiServer\feature;
+
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Tobyz\JsonApiServer\Exception\BadRequestException;
+use Tobyz\JsonApiServer\JsonApi;
+use Tobyz\JsonApiServer\Schema\Type;
+use Tobyz\Tests\JsonApiServer\AbstractTestCase;
+use Tobyz\Tests\JsonApiServer\MockAdapter;
+
+class AttributeWritableTest extends AbstractTestCase
+{
+    /**
+     * @var JsonApi
+     */
+    private $api;
+
+    /**
+     * @var MockAdapter
+     */
+    private $adapter;
+
+    public function setUp(): void
+    {
+        $this->api = new JsonApi('http://example.com');
+
+        $this->adapter = new MockAdapter([
+            '1' => (object) ['id' => '1']
+        ]);
+    }
+
+    public function test_attributes_are_readonly_by_default()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->updatable();
+            $type->attribute('readonly');
+        });
+
+        $this->expectException(BadRequestException::class);
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'readonly' => 'value',
+                        ]
+                    ]
+                ])
+        );
+    }
+
+    public function test_attributes_can_be_explicitly_writable()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->updatable();
+            $type->attribute('writable')->writable();
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+        $this->assertEquals('value', $this->adapter->models['1']->writable);
+    }
+
+    public function test_attributes_can_be_conditionally_writable()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->updatable();
+            $type->attribute('writable')
+                ->writable(function () { return true; });
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+        $this->assertEquals('value', $this->adapter->models['1']->writable);
+    }
+
+    public function test_attributes_can_be_conditionally_not_writable()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->updatable();
+            $type->attribute('writable')
+                ->writable(function () { return false; });
+        });
+
+        $this->expectException(BadRequestException::class);
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+    }
+
+    public function test_attribute_writable_callback_receives_correct_parameters()
+    {
+        $called = false;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->updatable();
+            $type->attribute('writable')
+                ->writable(function ($model, $request) use (&$called) {
+                    $this->assertSame($this->adapter->models['1'], $model);
+                    $this->assertInstanceOf(ServerRequestInterface::class, $request);
+
+                    return $called = true;
+                });
+        });
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertTrue($called);
+    }
+
+    public function test_attributes_can_be_explicitly_readonly()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->updatable();
+            $type->attribute('readonly')->readonly();
+        });
+
+        $this->expectException(BadRequestException::class);
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'readonly' => 'value',
+                        ]
+                    ]
+                ])
+        );
+    }
+
+    public function test_attributes_can_be_conditionally_readonly()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->updatable();
+            $type->attribute('readonly')
+                ->readonly(function () { return true; });
+        });
+
+        $this->expectException(BadRequestException::class);
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'readonly' => 'value',
+                        ]
+                    ]
+                ])
+        );
+    }
+
+    public function test_attribute_readonly_callback_receives_correct_parameters()
+    {
+        $called = false;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $type->updatable();
+            $type->attribute('readonly')
+                ->readonly(function ($model, $request) use (&$called) {
+                    $called = true;
+
+                    $this->assertSame($this->adapter->models['1'], $model);
+                    $this->assertInstanceOf(RequestInterface::class, $request);
+
+                    return false;
+                });
+        });
+
+        $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'readonly' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertTrue($called);
+    }
+
+    public function test_attributes_can_be_conditionally_not_readonly()
+    {
+        $this->api->resource('users', $this->adapter, function (Type $type) {
+            $type->updatable();
+            $type->attribute('writable')
+                ->readonly(function () { return false; });
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'writable' => 'value',
+                        ]
+                    ]
+                ])
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+        $this->assertEquals('value', $this->adapter->models['1']->writable);
+    }
+}
diff --git a/tests/feature/BasicTest.php b/tests/feature/BasicTest.php
new file mode 100644
index 0000000..c0bebeb
--- /dev/null
+++ b/tests/feature/BasicTest.php
@@ -0,0 +1,174 @@
+<?php
+
+/*
+ * This file is part of tobyz/json-api-server.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Tobyz\Tests\JsonApiServer\feature;
+
+use Tobyz\JsonApiServer\JsonApi;
+use Tobyz\JsonApiServer\Schema\Type;
+use Tobyz\Tests\JsonApiServer\AbstractTestCase;
+use Tobyz\Tests\JsonApiServer\MockAdapter;
+
+class BasicTest extends AbstractTestCase
+{
+    /**
+     * @var JsonApi
+     */
+    private $api;
+
+    public function setUp(): void
+    {
+        $this->api = new JsonApi('http://example.com');
+
+        $adapter = new MockAdapter([
+            '1' => (object) [
+                'id' => '1',
+                'name' => 'Toby',
+            ],
+            '2' => (object) [
+                'id' => '2',
+                'name' => 'Franz',
+            ],
+        ]);
+
+        $this->api->resource('users', $adapter, function (Type $type) {
+            $type->attribute('name')->writable();
+            $type->creatable();
+            $type->updatable();
+            $type->deletable();
+        });
+    }
+
+    public function test_show_resource()
+    {
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+
+        $this->assertJsonApiDocumentSubset([
+            'data' => [
+                'type' => 'users',
+                'id' => '1',
+                'attributes' => [
+                    'name' => 'Toby'
+                ],
+                'links' => [
+                    'self' => 'http://example.com/users/1'
+                ]
+            ]
+        ], $response->getBody());
+    }
+
+    public function test_list_resources()
+    {
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users')
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+
+        $this->assertJsonApiDocumentSubset([
+            'data' => [
+                [
+                    'type' => 'users',
+                    'id' => '1',
+                    'attributes' => [
+                        'name' => 'Toby'
+                    ],
+                    'links' => [
+                        'self' => 'http://example.com/users/1'
+                    ]
+                ],
+                [
+                    'type' => 'users',
+                    'id' => '2',
+                    'attributes' => [
+                        'name' => 'Franz'
+                    ],
+                    'links' => [
+                        'self' => 'http://example.com/users/2'
+                    ]
+                ]
+            ]
+        ], $response->getBody());
+    }
+
+    public function test_create_resource()
+    {
+        $response = $this->api->handle(
+            $this->buildRequest('POST', '/users')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'attributes' => [
+                            'name' => 'Bob',
+                        ],
+                    ],
+                ])
+        );
+
+        $this->assertEquals(201, $response->getStatusCode());
+
+        $this->assertJsonApiDocumentSubset([
+            'data' => [
+                'type' => 'users',
+                'id' => '1',
+                'attributes' => [
+                    'name' => 'Bob',
+                ],
+                'links' => [
+                    'self' => 'http://example.com/users/1',
+                ],
+            ],
+        ], $response->getBody());
+    }
+
+    public function test_update_resource()
+    {
+        $response = $this->api->handle(
+            $this->buildRequest('PATCH', '/users/1')
+                ->withParsedBody([
+                    'data' => [
+                        'type' => 'users',
+                        'id' => '1',
+                        'attributes' => [
+                            'name' => 'Bob',
+                        ],
+                    ],
+                ])
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+
+        $this->assertJsonApiDocumentSubset([
+            'data' => [
+                'type' => 'users',
+                'id' => '1',
+                'attributes' => [
+                    'name' => 'Bob',
+                ],
+                'links' => [
+                    'self' => 'http://example.com/users/1',
+                ],
+            ],
+        ], $response->getBody());
+    }
+
+    public function test_delete_resource()
+    {
+        $response = $this->api->handle(
+            $this->buildRequest('DELETE', '/users/1')
+        );
+
+        $this->assertEquals(204, $response->getStatusCode());
+    }
+}
diff --git a/tests/feature/FieldVisibilityTest.php b/tests/feature/FieldVisibilityTest.php
new file mode 100644
index 0000000..2247b97
--- /dev/null
+++ b/tests/feature/FieldVisibilityTest.php
@@ -0,0 +1,237 @@
+<?php
+
+/*
+ * This file is part of tobyz/json-api-server.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Tobyz\Tests\JsonApiServer\feature;
+
+use Psr\Http\Message\RequestInterface;
+use Tobyz\JsonApiServer\JsonApi;
+use Tobyz\JsonApiServer\Schema\Type;
+use Tobyz\Tests\JsonApiServer\AbstractTestCase;
+use Tobyz\Tests\JsonApiServer\MockAdapter;
+
+class FieldVisibilityTest extends AbstractTestCase
+{
+    /**
+     * @var JsonApi
+     */
+    private $api;
+
+    /**
+     * @var MockAdapter
+     */
+    private $adapter;
+
+    public function setUp(): void
+    {
+        $this->api = new JsonApi('http://example.com');
+
+        $this->adapter = new MockAdapter([
+            '1' => (object) ['id' => '1']
+        ]);
+    }
+
+    public function test_fields_are_visible_by_default()
+    {
+        $this->api->resource('users', new MockAdapter, function (Type $type) {
+            $type->attribute('visibleAttribute');
+            $type->hasOne('visibleHasOne');
+            $type->hasMany('visibleHasMany');
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $document = json_decode($response->getBody(), true);
+        $attributes = $document['data']['attributes'] ?? [];
+        $relationships = $document['data']['relationships'] ?? [];
+
+        $this->assertArrayHasKey('visibleAttribute', $attributes);
+        $this->assertArrayHasKey('visibleHasOne', $relationships);
+        $this->assertArrayHasKey('visibleHasMany', $relationships);
+    }
+
+    public function test_fields_can_be_explicitly_visible()
+    {
+        $this->api->resource('users', new MockAdapter, function (Type $type) {
+            $type->attribute('visibleAttribute')->visible();
+            $type->hasOne('visibleHasOne')->visible();
+            $type->hasMany('visibleHasMany')->visible();
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $document = json_decode($response->getBody(), true);
+        $attributes = $document['data']['attributes'] ?? [];
+        $relationships = $document['data']['relationships'] ?? [];
+
+        $this->assertArrayHasKey('visibleAttribute', $attributes);
+        $this->assertArrayHasKey('visibleHasOne', $relationships);
+        $this->assertArrayHasKey('visibleHasMany', $relationships);
+    }
+
+    public function test_fields_can_be_conditionally_visible()
+    {
+        $this->api->resource('users', new MockAdapter, function (Type $type) {
+            $type->attribute('visibleAttribute')
+                ->visible(function () { return true; });
+
+            $type->attribute('hiddenAttribute')
+                ->visible(function () { return false; });
+
+            $type->hasOne('visibleHasOne')
+                ->visible(function () { return true; });
+
+            $type->hasOne('hiddenHasOne')
+                ->visible(function () { return false; });
+
+            $type->hasMany('visibleHasMany')
+                ->visible(function () { return true; });
+
+            $type->hasMany('hiddenHasMany')
+                ->visible(function () { return false; });
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $document = json_decode($response->getBody(), true);
+        $attributes = $document['data']['attributes'] ?? [];
+        $relationships = $document['data']['relationships'] ?? [];
+
+        $this->assertArrayHasKey('visibleAttribute', $attributes);
+        $this->assertArrayHasKey('visibleHasOne', $relationships);
+        $this->assertArrayHasKey('visibleHasMany', $relationships);
+
+        $this->assertArrayNotHasKey('hiddenAttribute', $attributes);
+        $this->assertArrayNotHasKey('hiddenHasOne', $relationships);
+        $this->assertArrayNotHasKey('hiddenHasMany', $relationships);
+    }
+
+    public function test_visible_callback_receives_correct_parameters()
+    {
+        $called = 0;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $callback = function ($model, $request) use (&$called) {
+                $this->assertSame($this->adapter->models['1'], $model);
+                $this->assertInstanceOf(RequestInterface::class, $request);
+                $called++;
+            };
+
+            $type->attribute('attribute')
+                ->visible($callback);
+
+            $type->hasOne('hasOne')
+                ->visible($callback);
+
+            $type->hasMany('hasMany')
+                ->visible($callback);
+        });
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $this->assertEquals(3, $called);
+    }
+
+    public function test_fields_can_be_explicitly_hidden()
+    {
+        $this->api->resource('users', new MockAdapter, function (Type $type) {
+            $type->attribute('hiddenAttribute')->hidden();
+            $type->hasOne('hiddenHasOne')->hidden();
+            $type->hasMany('hiddenHasMany')->hidden();
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $document = json_decode($response->getBody(), true);
+        $attributes = $document['data']['attributes'] ?? [];
+        $relationships = $document['data']['relationships'] ?? [];
+
+        $this->assertArrayNotHasKey('hiddenAttribute', $attributes);
+        $this->assertArrayNotHasKey('hiddenHasOne', $relationships);
+        $this->assertArrayNotHasKey('hiddenHasMany', $relationships);
+    }
+
+    public function test_fields_can_be_conditionally_hidden()
+    {
+        $this->api->resource('users', new MockAdapter, function (Type $type) {
+            $type->attribute('visibleAttribute')
+                ->hidden(function () { return false; });
+
+            $type->attribute('hiddenAttribute')
+                ->hidden(function () { return true; });
+
+            $type->hasOne('visibleHasOne')
+                ->hidden(function () { return false; });
+
+            $type->hasOne('hiddenHasOne')
+                ->hidden(function () { return true; });
+
+            $type->hasMany('visibleHasMany')
+                ->hidden(function () { return false; });
+
+            $type->hasMany('hiddenHasMany')
+                ->hidden(function () { return true; });
+        });
+
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $document = json_decode($response->getBody(), true);
+        $attributes = $document['data']['attributes'] ?? [];
+        $relationships = $document['data']['relationships'] ?? [];
+
+        $this->assertArrayHasKey('visibleAttribute', $attributes);
+        $this->assertArrayHasKey('visibleHasOne', $relationships);
+        $this->assertArrayHasKey('visibleHasMany', $relationships);
+
+        $this->assertArrayNotHasKey('hiddenAttribute', $attributes);
+        $this->assertArrayNotHasKey('hiddenHasOne', $relationships);
+        $this->assertArrayNotHasKey('hiddenHasMany', $relationships);
+    }
+
+    public function test_hidden_callback_receives_correct_parameters()
+    {
+        $called = 0;
+
+        $this->api->resource('users', $this->adapter, function (Type $type) use (&$called) {
+            $callback = function ($model, $request) use (&$called) {
+                $this->assertSame($this->adapter->models['1'], $model);
+                $this->assertInstanceOf(RequestInterface::class, $request);
+                $called++;
+            };
+
+            $type->attribute('attribute')
+                ->hidden($callback);
+
+            $type->hasOne('hasOne')
+                ->hidden($callback);
+
+            $type->hasMany('hasMany')
+                ->hidden($callback);
+        });
+
+        $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $this->assertEquals(3, $called);
+    }
+}
diff --git a/tests/specification/ContentNegotiationTest.php b/tests/specification/ContentNegotiationTest.php
new file mode 100644
index 0000000..b24d51e
--- /dev/null
+++ b/tests/specification/ContentNegotiationTest.php
@@ -0,0 +1,77 @@
+<?php
+
+/*
+ * This file is part of tobyz/json-api-server.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Tobyz\Tests\JsonApiServer\specification;
+
+use Tobyz\JsonApiServer\JsonApi;
+use Tobyz\JsonApiServer\Exception\NotAcceptableException;
+use Tobyz\JsonApiServer\Exception\UnsupportedMediaTypeException;
+use Tobyz\JsonApiServer\Schema\Type;
+use Tobyz\Tests\JsonApiServer\AbstractTestCase;
+use Tobyz\Tests\JsonApiServer\MockAdapter;
+
+class ContentNegotiationTest extends AbstractTestCase
+{
+    /**
+     * @var JsonApi
+     */
+    private $api;
+
+    public function setUp(): void
+    {
+        $this->api = new JsonApi('http://example.com');
+        $this->api->resource('users', new MockAdapter(), function (Type $type) {
+            // no fields
+        });
+    }
+
+    public function testJsonApiContentTypeIsReturned()
+    {
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+        );
+
+        $this->assertEquals(
+            'application/vnd.api+json',
+            $response->getHeaderLine('Content-Type')
+        );
+    }
+
+    public function testErrorWhenValidRequestContentTypeHasParameters()
+    {
+        $request = $this->buildRequest('PATCH', '/users/1')
+            ->withHeader('Content-Type', 'application/vnd.api+json;profile="http://example.com/last-modified"');
+
+        $this->expectException(UnsupportedMediaTypeException::class);
+
+        $this->api->handle($request);
+    }
+
+    public function testErrorWhenAllValidAcceptsHaveParameters()
+    {
+        $request = $this->buildRequest('GET', '/users/1')
+            ->withHeader('Accept', 'application/vnd.api+json;profile="http://example.com/last-modified", application/vnd.api+json;profile="http://example.com/versioning"');
+
+        $this->expectException(NotAcceptableException::class);
+
+        $this->api->handle($request);
+    }
+
+    public function testSuccessWhenOnlySomeAcceptsHaveParameters()
+    {
+        $response = $this->api->handle(
+            $this->buildRequest('GET', '/users/1')
+                ->withHeader('Accept', 'application/vnd.api+json;profile="http://example.com/last-modified", application/vnd.api+json')
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+    }
+}
diff --git a/tests/unit/MediaTypesTest.php b/tests/unit/MediaTypesTest.php
new file mode 100644
index 0000000..8200ba4
--- /dev/null
+++ b/tests/unit/MediaTypesTest.php
@@ -0,0 +1,72 @@
+<?php
+
+/*
+ * This file is part of JSON-API.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Tobyz\Tests\JsonApiServer\unit\Http;
+
+use PHPUnit\Framework\TestCase;
+use Tobyz\JsonApiServer\Http\MediaTypes;
+
+class MediaTypesTest extends TestCase
+{
+    public function testContainsOnExactMatch()
+    {
+        $header = new MediaTypes('application/json');
+
+        $this->assertTrue(
+            $header->containsExactly('application/json')
+        );
+    }
+
+    public function testContainsDoesNotMatchWithExtraParameters()
+    {
+        $header = new MediaTypes('application/json; profile=foo');
+
+        $this->assertFalse(
+            $header->containsExactly('application/json')
+        );
+    }
+
+    public function testContainsMatchesWhenOnlyWeightIsProvided()
+    {
+        $header = new MediaTypes('application/json; q=0.8');
+
+        $this->assertTrue(
+            $header->containsExactly('application/json')
+        );
+    }
+
+    public function testContainsDoesNotMatchWithExtraParametersBeforeWeight()
+    {
+        $header = new MediaTypes('application/json; profile=foo; q=0.8');
+
+        $this->assertFalse(
+            $header->containsExactly('application/json')
+        );
+    }
+
+    public function testContainsMatchesWithExtraParametersAfterWeight()
+    {
+        $header = new MediaTypes('application/json; q=0.8; profile=foo');
+
+        $this->assertTrue(
+            $header->containsExactly('application/json')
+        );
+    }
+
+    public function testContainsMatchesWhenOneOfMultipleMediaTypesIsValid()
+    {
+        $header = new MediaTypes('application/json; profile=foo, application/json; q=0.6');
+
+        $this->assertTrue(
+            $header->containsExactly('application/json')
+        );
+    }
+}