diff --git a/includes/entity.inc b/includes/entity.inc
index be24499..14be2e8 100644
--- a/includes/entity.inc
+++ b/includes/entity.inc
@@ -6,6 +6,167 @@
  */
 
 /**
+ * Interface EntityInterface
+ */
+interface EntityInterface {
+  /**
+   * Returns the internal, numeric identifier.
+   *
+   * Returns the numeric identifier, even if the entity type has specified a
+   * name key. In the latter case, the numeric identifier is supposed to be used
+   * when dealing generically with entities or internally to refer to an entity,
+   * i.e. in a relational database. If unsure, use Entity:identifier().
+   */
+  public function internalIdentifier();
+
+  /**
+   * Returns the entity identifier, i.e. the entities name or numeric id.
+   *
+   * @return
+   *   The identifier of the entity. If the entity type makes use of a name key,
+   *   the name is returned, else the numeric id.
+   *
+   * @see entity_id()
+   */
+  public function identifier();
+
+  /**
+   * Returns the info of the type of the entity.
+   *
+   * @see entity_get_info()
+   */
+  public function entityInfo();
+
+  /**
+   * Returns the type of the entity.
+   */
+  public function entityType();
+
+  /**
+   * Returns the bundle of the entity.
+   *
+   * @return
+   *   The bundle of the entity. Defaults to the entity type if the entity type
+   *   does not make use of different bundles.
+   */
+  public function bundle();
+
+  /**
+   * Returns the EntityMetadataWrapper of the entity.
+   *
+   * @return EntityDrupalWrapper
+   *   An EntityMetadataWrapper containing the entity.
+   */
+  public function wrapper();
+
+  /**
+   * Returns the label of the entity.
+   *
+   * Modules may alter the label by specifying another 'label callback' using
+   * hook_entity_info_alter().
+   *
+   * @see entity_label()
+   */
+  public function label();
+
+  /**
+   * Returns the uri of the entity just as entity_uri().
+   *
+   * Modules may alter the uri by specifying another 'uri callback' using
+   * hook_entity_info_alter().
+   *
+   * @see entity_uri()
+   */
+  public function uri();
+
+  /**
+   * Checks if the entity has a certain exportable status.
+   *
+   * @param $status
+   *   A status constant, i.e. one of ENTITY_CUSTOM, ENTITY_IN_CODE,
+   *   ENTITY_OVERRIDDEN or ENTITY_FIXED.
+   *
+   * @return bool
+   *   For exportable entities TRUE if the entity has the status, else FALSE.
+   *   In case the entity is not exportable, NULL is returned.
+   *
+   * @see entity_has_status()
+   */
+  public function hasStatus($status);
+
+  /**
+   * Permanently saves the entity.
+   *
+   * @see entity_save()
+   */
+  public function save();
+
+  /**
+   * Permanently deletes the entity.
+   *
+   * @see entity_delete()
+   */
+  public function delete();
+
+  /**
+   * Exports the entity.
+   *
+   * @see entity_export()
+   */
+  public function export($prefix = '');
+
+  /**
+   * Generate an array for rendering the entity.
+   *
+   * @see entity_view()
+   */
+  public function view($view_mode = 'full', $langcode = NULL, $page = NULL);
+
+  /**
+   * Builds a structured array representing the entity's content.
+   *
+   * @see entity_build_content()
+   */
+  public function buildContent($view_mode = 'full', $langcode = NULL);
+
+  /**
+   * Gets the raw, translated value of a property or field.
+   *
+   * Supports retrieving field translations as well as i18n string translations.
+   *
+   * Note that this returns raw data values, which might not reflect what
+   * has been declared for hook_entity_property_info() as no 'getter callbacks'
+   * are invoked or no referenced entities are loaded. For retrieving values
+   * reflecting the property info make use of entity metadata wrappers, see
+   * entity_metadata_wrapper().
+   *
+   * @param $property
+   *   The name of the property to return; e.g., 'title'.
+   * @param $langcode
+   *   (optional) The language code of the language to which the value should
+   *   be translated. If set to NULL, the default display language is being
+   *   used.
+   *
+   * @return
+   *   The raw, translated property value; or the raw, un-translated value if no
+   *   translation is available.
+   *
+   * @todo Implement an analogous setTranslation() method for updating.
+   */
+  public function getTranslation($property, $langcode = NULL);
+
+  /**
+   * Checks whether the entity is the default revision.
+   *
+   * @return Boolean
+   *
+   * @see entity_revision_is_default()
+   */
+  public function isDefaultRevision();
+
+}
+
+/**
  * A common class for entities.
  *
  * It's suggested, but not required, to extend this class and to override
@@ -25,7 +186,7 @@
  *   public $count = 0;
  * @endcode
  */
-class Entity {
+class Entity implements EntityInterface {
 
   protected $entityType;
   protected $entityInfo;
@@ -34,9 +195,7 @@ class Entity {
   protected $wrapper;
 
   /**
-   * Creates a new entity.
-   *
-   * @see entity_create()
+   * {@inheritdoc}
    */
   public function __construct(array $values = array(), $entityType = NULL) {
     if (empty($entityType)) {
@@ -61,62 +220,42 @@ class Entity {
   }
 
   /**
-   * Returns the internal, numeric identifier.
-   *
-   * Returns the numeric identifier, even if the entity type has specified a
-   * name key. In the latter case, the numeric identifier is supposed to be used
-   * when dealing generically with entities or internally to refer to an entity,
-   * i.e. in a relational database. If unsure, use Entity:identifier().
+   * {@inheritdoc}
    */
   public function internalIdentifier() {
     return isset($this->{$this->idKey}) ? $this->{$this->idKey} : NULL;
   }
 
   /**
-   * Returns the entity identifier, i.e. the entities name or numeric id.
-   *
-   * @return
-   *   The identifier of the entity. If the entity type makes use of a name key,
-   *   the name is returned, else the numeric id.
-   *
-   * @see entity_id()
+   * {@inheritdoc}
    */
   public function identifier() {
     return isset($this->{$this->nameKey}) ? $this->{$this->nameKey} : NULL;
   }
 
   /**
-   * Returns the info of the type of the entity.
-   *
-   * @see entity_get_info()
+   * {@inheritdoc}
    */
   public function entityInfo() {
     return $this->entityInfo;
   }
 
   /**
-   * Returns the type of the entity.
+   * {@inheritdoc}
    */
   public function entityType() {
     return $this->entityType;
   }
 
   /**
-   * Returns the bundle of the entity.
-   *
-   * @return
-   *   The bundle of the entity. Defaults to the entity type if the entity type
-   *   does not make use of different bundles.
+   * {@inheritdoc}
    */
   public function bundle() {
     return !empty($this->entityInfo['entity keys']['bundle']) ? $this->{$this->entityInfo['entity keys']['bundle']} : $this->entityType;
   }
 
   /**
-   * Returns the EntityMetadataWrapper of the entity.
-   *
-   * @return EntityDrupalWrapper
-   *   An EntityMetadataWrapper containing the entity.
+   * {@inheritdoc}
    */
   public function wrapper() {
     if (empty($this->wrapper)) {
@@ -130,12 +269,7 @@ class Entity {
   }
 
   /**
-   * Returns the label of the entity.
-   *
-   * Modules may alter the label by specifying another 'label callback' using
-   * hook_entity_info_alter().
-   *
-   * @see entity_label()
+   * {@inheritdoc}
    */
   public function label() {
     // If the default label flag is enabled, this is being invoked recursively.
@@ -165,12 +299,7 @@ class Entity {
   }
 
   /**
-   * Returns the uri of the entity just as entity_uri().
-   *
-   * Modules may alter the uri by specifying another 'uri callback' using
-   * hook_entity_info_alter().
-   *
-   * @see entity_uri()
+   * {@inheritdoc}
    */
   public function uri() {
     if (isset($this->entityInfo['uri callback']) && $this->entityInfo['uri callback'] == 'entity_class_uri') {
@@ -188,17 +317,7 @@ class Entity {
   }
 
   /**
-   * Checks if the entity has a certain exportable status.
-   *
-   * @param $status
-   *   A status constant, i.e. one of ENTITY_CUSTOM, ENTITY_IN_CODE,
-   *   ENTITY_OVERRIDDEN or ENTITY_FIXED.
-   *
-   * @return
-   *   For exportable entities TRUE if the entity has the status, else FALSE.
-   *   In case the entity is not exportable, NULL is returned.
-   *
-   * @see entity_has_status()
+   * {@inheritdoc}
    */
   public function hasStatus($status) {
     if (!empty($this->entityInfo['exportable'])) {
@@ -207,18 +326,14 @@ class Entity {
   }
 
   /**
-   * Permanently saves the entity.
-   *
-   * @see entity_save()
+   * {@inheritdoc}
    */
   public function save() {
     return entity_get_controller($this->entityType)->save($this);
   }
 
   /**
-   * Permanently deletes the entity.
-   *
-   * @see entity_delete()
+   * {@inheritdoc}
    */
   public function delete() {
     $id = $this->identifier();
@@ -228,55 +343,28 @@ class Entity {
   }
 
   /**
-   * Exports the entity.
-   *
-   * @see entity_export()
+   * {@inheritdoc}
    */
   public function export($prefix = '') {
     return entity_get_controller($this->entityType)->export($this, $prefix);
   }
 
   /**
-   * Generate an array for rendering the entity.
-   *
-   * @see entity_view()
+   * {@inheritdoc}
    */
   public function view($view_mode = 'full', $langcode = NULL, $page = NULL) {
     return entity_get_controller($this->entityType)->view(array($this), $view_mode, $langcode, $page);
   }
 
   /**
-   * Builds a structured array representing the entity's content.
-   *
-   * @see entity_build_content()
+   * {@inheritdoc}
    */
   public function buildContent($view_mode = 'full', $langcode = NULL) {
     return entity_get_controller($this->entityType)->buildContent($this, $view_mode, $langcode);
   }
 
   /**
-   * Gets the raw, translated value of a property or field.
-   *
-   * Supports retrieving field translations as well as i18n string translations.
-   *
-   * Note that this returns raw data values, which might not reflect what
-   * has been declared for hook_entity_property_info() as no 'getter callbacks'
-   * are invoked or no referenced entities are loaded. For retrieving values
-   * reflecting the property info make use of entity metadata wrappers, see
-   * entity_metadata_wrapper().
-   *
-   * @param $property_name
-   *   The name of the property to return; e.g., 'title'.
-   * @param $langcode
-   *   (optional) The language code of the language to which the value should
-   *   be translated. If set to NULL, the default display language is being
-   *   used.
-   *
-   * @return
-   *   The raw, translated property value; or the raw, un-translated value if no
-   *   translation is available.
-   *
-   * @todo Implement an analogous setTranslation() method for updating.
+   * {@inheritdoc}
    */
   public function getTranslation($property, $langcode = NULL) {
     $all_info = entity_get_all_property_info($this->entityType);
@@ -296,11 +384,7 @@ class Entity {
   }
 
   /**
-   * Checks whether the entity is the default revision.
-   *
-   * @return Boolean
-   *
-   * @see entity_revision_is_default()
+   * {@inheritdoc}
    */
   public function isDefaultRevision() {
     if (!empty($this->entityInfo['entity keys']['revision'])) {