diff --git a/core/lib/Drupal/Component/Plugin/DerivativeInspectionInterface.php b/core/lib/Drupal/Component/Plugin/DerivativeInspectionInterface.php
index 08e771a..4dbd9d5 100644
--- a/core/lib/Drupal/Component/Plugin/DerivativeInspectionInterface.php
+++ b/core/lib/Drupal/Component/Plugin/DerivativeInspectionInterface.php
@@ -8,8 +8,24 @@
 namespace Drupal\Component\Plugin;
 
 /**
- * @todo.
+ * Provides a plugin interface for providing derivative metadata inspection.
  */
-class DerivativeInspectionInterface {
+interface DerivativeInspectionInterface {
+
+  /**
+   * Returns the base_plugin_id of the plugin instance.
+   *
+   * @return string
+   *   The base_plugin_id of the plugin instance.
+   */
+  public function getBasePluginId();
+
+  /**
+   * Returns the derivative_id of the plugin instance.
+   *
+   * @return string|null
+   *   The derivative_id of the plugin instance NULL otherwise.
+   */
+  public function getDerivativeId();
 
 }
diff --git a/core/lib/Drupal/Component/Plugin/PluginBase.php b/core/lib/Drupal/Component/Plugin/PluginBase.php
index d4e00bb..8c3f274 100644
--- a/core/lib/Drupal/Component/Plugin/PluginBase.php
+++ b/core/lib/Drupal/Component/Plugin/PluginBase.php
@@ -9,7 +9,7 @@
 /**
  * Base class for plugins wishing to support metadata inspection.
  */
-abstract class PluginBase implements PluginInspectionInterface {
+abstract class PluginBase implements PluginInspectionInterface, DerivativeInspectionInterface {
 
   /**
    * The plugin_id.
diff --git a/core/lib/Drupal/Component/Plugin/PluginInspectionInterface.php b/core/lib/Drupal/Component/Plugin/PluginInspectionInterface.php
index eedd3ab..71fee3b 100644
--- a/core/lib/Drupal/Component/Plugin/PluginInspectionInterface.php
+++ b/core/lib/Drupal/Component/Plugin/PluginInspectionInterface.php
@@ -23,22 +23,6 @@
   public function getPluginId();
 
   /**
-   * Returns the base_plugin_id of the plugin instance.
-   *
-   * @return string
-   *   The base_plugin_id of the plugin instance.
-   */
-  public function getBasePluginId();
-
-  /**
-   * Returns the derivative_id of the plugin instance.
-   *
-   * @return string|null
-   *   The derivative_id of the plugin instance NULL otherwise.
-   */
-  public function getDerivativeId();
-
-  /**
    * Returns the definition of the plugin implementation.
    *
    * @return array