diff --git a/core/lib/Drupal/Component/Plugin/Context/ContextInterface.php b/core/lib/Drupal/Component/Plugin/Context/ContextInterface.php
index 512605a..c5cd743 100644
--- a/core/lib/Drupal/Component/Plugin/Context/ContextInterface.php
+++ b/core/lib/Drupal/Component/Plugin/Context/ContextInterface.php
@@ -7,8 +7,6 @@
 
 namespace Drupal\Component\Plugin\Context;
 
-use Drupal\Component\Plugin\Exception\ContextException;
-
 /**
  * A generic context interface for wrapping data a plugin needs to operate.
  */
@@ -18,8 +16,9 @@
    * Sets the context value.
    *
    * @param mixed $value
-   *   The value of this context, generally an object based upon the class
-   *   matching the definition passed to setContextDefinition().
+   *   The value of this context, matching the context definition.
+   *
+   * @see \Drupal\Component\Plugin\Context\ContextInterface::setContextDefinition().
    */
   public function setContextValue($value);
 
@@ -27,7 +26,7 @@ public function setContextValue($value);
    * Gets the context value.
    *
    * @return mixed
-   *   The currently set context value within this class.
+   *   The currently set context value, or NULL if it is not set.
    */
   public function getContextValue();
 
diff --git a/core/lib/Drupal/Component/Plugin/ContextAwarePluginBase.php b/core/lib/Drupal/Component/Plugin/ContextAwarePluginBase.php
index c6ffc3d..2b97103 100644
--- a/core/lib/Drupal/Component/Plugin/ContextAwarePluginBase.php
+++ b/core/lib/Drupal/Component/Plugin/ContextAwarePluginBase.php
@@ -28,18 +28,18 @@
    */
   public function getContextDefinitions() {
     $definition = $this->getDefinition();
-    return !empty($definition['context']) ? $definition['context'] : NULL;
+    return !empty($definition['context']) ? $definition['context'] : array();
   }
 
   /**
    * Implements \Drupal\Component\Plugin\ContextAwarePluginInterface::getContextDefinition().
    */
-  public function getContextDefinition($key) {
+  public function getContextDefinition($name) {
     $definition = $this->getDefinition();
-    if (empty($definition['context'][$key])) {
-      throw new PluginException("The $key context is not a valid context.");
+    if (empty($definition['context'][$name])) {
+      throw new PluginException("The $name context is not a valid context.");
     }
-    return $definition['context'][$key];
+    return $definition['context'][$name];
   }
 
   /**
@@ -47,19 +47,15 @@ public function getContextDefinition($key) {
    */
   public function getContexts() {
     $definitions = $this->getContextDefinitions();
-    // If there are no contexts defined by the plugin, return an empty array.
-    if (empty($definitions)) {
-      return array();
-    }
-    if (empty($this->context)) {
+    if ($definitions && empty($this->context)) {
       throw new PluginException("There are no set contexts.");
     }
     $contexts = array();
-    foreach (array_keys($definitions) as $key) {
-      if (empty($this->context[$key])) {
-        throw new PluginException("The $key context is not yet set.");
+    foreach (array_keys($definitions) as $name) {
+      if (empty($this->context[$name])) {
+        throw new PluginException("The $name context is not yet set.");
       }
-      $contexts[$key] = $this->context[$key];
+      $contexts[$name] = $this->context[$name];
     }
     return $contexts;
   }
@@ -67,25 +63,24 @@ public function getContexts() {
   /**
    * Implements \Drupal\Component\Plugin\ContextAwarePluginInterface::getContext().
    */
-  public function getContext($key) {
+  public function getContext($name) {
     // Check for a valid context definition.
-    $this->getContextDefinition($key);
+    $this->getContextDefinition($name);
     // Check for a valid context value.
-    if (empty($this->context[$key])) {
-      throw new PluginException("The $key context is not yet set.");
+    if (!isset($this->context[$name])) {
+      throw new PluginException("The $name context is not yet set.");
     }
 
-    return $this->context[$key];
+    return $this->context[$name];
   }
 
   /**
    * Implements \Drupal\Component\Plugin\ContextAwarePluginInterface::getContextValues().
    */
   public function getContextValues() {
-    $definitions = (array) $this->getContextDefinitions();
     $values = array();
-    foreach ($definitions as $key => $definition) {
-      $values[$key] = isset($this->context[$key]) ? $this->context[$key]->getContextValue() : NULL;
+    foreach ($this->getContextDefinitions() as $name => $definition) {
+      $values[$name] = isset($this->context[$name]) ? $this->context[$name]->getContextValue() : NULL;
     }
     return $values;
   }
@@ -93,20 +88,20 @@ public function getContextValues() {
   /**
    * Implements \Drupal\Component\Plugin\ContextAwarePluginInterface::getContextValue().
    */
-  public function getContextValue($key) {
-    return $this->getContext($key)->getContextValue();
+  public function getContextValue($name) {
+    return $this->getContext($name)->getContextValue();
   }
 
   /**
    * Implements \Drupal\Component\Plugin\ContextAwarePluginInterface::setContextValue().
    */
-  public function setContextValue($key, $value) {
-    $context_definition = $this->getContextDefinition($key);
-    $this->context[$key] = new Context($context_definition);
-    $this->context[$key]->setContextValue($value);
+  public function setContextValue($name, $value) {
+    $context_definition = $this->getContextDefinition($name);
+    $this->context[$name] = new Context($context_definition);
+    $this->context[$name]->setContextValue($value);
 
     // Verify the provided value validates.
-    $violations = $this->context[$key]->validate();
+    $violations = $this->context[$name]->validate();
     if (count($violations) > 0) {
       throw new PluginException("The provided context value does not pass validation.");
     }
@@ -121,14 +116,12 @@ public function validate() {
     // @todo: Implement symfony validator API to let the validator traverse
     // and set property paths accordingly.
 
-    if ($definitions = $this->getContextDefinitions()) {
-      foreach ($definitions as $key => $definition) {
-        // Validate any set values.
-        if (isset($this->context[$key])) {
-          $violations->addAll($this->context[$key]->validate());
-        }
-        // @todo: If no value is set, make sure any mapping is validated.
+    foreach ($this->getContextDefinitions() as $name => $definition) {
+      // Validate any set values.
+      if (isset($this->context[$name])) {
+        $violations->addAll($this->context[$name]->validate());
       }
+      // @todo: If no value is set, make sure any mapping is validated.
     }
     return $violations;
   }
diff --git a/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php b/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php
index 086a25f..a90f787 100644
--- a/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php
+++ b/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php
@@ -8,34 +8,36 @@
 namespace Drupal\Component\Plugin;
 
 use Drupal\Component\Plugin\Exception\PluginException;
-use Drupal\Component\Plugin\Context\Context;
 
 /**
  * Interface for defining context aware plugins.
+ *
+ * Context aware plugins can specify an array of context definitions keyed by
+ * context name at the plugin definition under the "context" key.
  */
 interface ContextAwarePluginInterface extends PluginInspectionInterface {
 
   /**
    * Gets the context definitions of the plugin.
    *
-   * @return array|null
-   *   The context definitions if set, otherwise NULL.
+   * @return array
+   *   The array of context definitions, keyed by context name.
    */
   public function getContextDefinitions();
 
   /**
-   * Gets the a specific context definition of the plugin.
+   * Gets a specific context definition of the plugin.
    *
-   * @param string $key
+   * @param string $name
    *   The name of the context in the plugin definition.
    *
    * @throws \Drupal\Component\Plugin\Exception\PluginException
-   *   If the requested definition is not set.
+   *   If the requested context is not defined.
    *
    * @return array
    *   The definition against which the context value must validate.
    */
-  public function getContextDefinition($key);
+  public function getContextDefinition($name);
 
   /**
    * Gets the defined contexts.
@@ -51,9 +53,8 @@ public function getContexts();
   /**
    * Gets a defined context.
    *
-   * @param string $key
-   *   The name of the context in the plugin configuration. This string is
-   *   usually identical to the representative string in the plugin definition.
+   * @param string $name
+   *   The name of the context in the plugin definition.
    *
    * @throws \Drupal\Component\Plugin\Exception\PluginException
    *   If the requested context is not set.
@@ -61,13 +62,13 @@ public function getContexts();
    * @return \Drupal\Component\Plugin\Context\ContextInterface
    *   The context object.
    */
-  public function getContext($key);
+  public function getContext($name);
 
   /**
    * Gets the values for all defined contexts.
    *
    * @return array
-   *   An array of set context values, keyed by context key. If a context is
+   *   An array of set context values, keyed by context name. If a context is
    *   unset its value is returned as NULL.
    */
   public function getContextValues();
@@ -75,9 +76,8 @@ public function getContextValues();
   /**
    * Gets the value for a defined context.
    *
-   * @param string $key
-   *   The name of the context in the plugin configuration. This string is
-   *   usually identical to the representative string in the plugin definition.
+   * @param string $name
+   *   The name of the context in the plugin configuration.
    *
    * @throws \Drupal\Component\Plugin\Exception\PluginException
    *   If the requested context is not set.
@@ -85,15 +85,15 @@ public function getContextValues();
    * @return mixed
    *   The currently set context value.
    */
-  public function getContextValue($key);
+  public function getContextValue($name);
 
   /**
    * Sets the value for a defined context.
    *
-   * @param string $key
+   * @param string $name
    *   The name of the context in the plugin definition.
    * @param mixed $value
-   *   The variable to set the context to. This should validate against the
+   *   The value to set the context to. The value has to validate against the
    *   provided context definition.
    *
    * @throws \Drupal\Component\Plugin\Exception\PluginException
@@ -102,7 +102,7 @@ public function getContextValue($key);
    * @return \Drupal\Component\Plugin\ContextAwarePluginInterface.
    *   A context aware plugin object for chaining.
    */
-  public function setContextValue($key, $value);
+  public function setContextValue($name, $value);
 
   /**
    * Validates the set values for the defined contexts.
diff --git a/core/lib/Drupal/Core/Condition/ConditionInterface.php b/core/lib/Drupal/Core/Condition/ConditionInterface.php
index 82c220a..00538ba 100644
--- a/core/lib/Drupal/Core/Condition/ConditionInterface.php
+++ b/core/lib/Drupal/Core/Condition/ConditionInterface.php
@@ -11,11 +11,13 @@
 
 /**
  * An interface for condition plugins.
+ *
+ * @see \Drupal\Core\Executable\ExecutableInterface
  */
 interface ConditionInterface extends ExecutableInterface {
 
   /**
-   * Determines whether condition result will be negaeted.
+   * Determines whether condition result will be negated.
    *
    * @return boolean
    *   Whether the condition result will be negated.
@@ -23,9 +25,10 @@
   public function isNegated();
 
   /**
-   * Evaluate the condition and return TRUE or FALSE accordingly
+   * Evaluates the condition and returns TRUE or FALSE accordingly.
    *
    * @return bool
+   *   TRUE if the condition has been met, FALSE otherwise.
    */
   public function evaluate();
 
diff --git a/core/lib/Drupal/Core/Condition/ConditionManager.php b/core/lib/Drupal/Core/Condition/ConditionManager.php
index 847a8e7..c7cdb60 100644
--- a/core/lib/Drupal/Core/Condition/ConditionManager.php
+++ b/core/lib/Drupal/Core/Condition/ConditionManager.php
@@ -15,7 +15,6 @@
 use Drupal\Core\Plugin\Discovery\AlterDecorator;
 use Drupal\Core\Plugin\Discovery\AnnotatedClassDiscovery;
 use Drupal\Core\Plugin\Discovery\CacheDecorator;
-use Drupal\Core\Processor\ProcessorManager;
 
 /**
  * A plugin manager for condition plugins.
diff --git a/core/lib/Drupal/Core/Executable/ExecutableInterface.php b/core/lib/Drupal/Core/Executable/ExecutableInterface.php
index efb9b86..f6f5fed 100644
--- a/core/lib/Drupal/Core/Executable/ExecutableInterface.php
+++ b/core/lib/Drupal/Core/Executable/ExecutableInterface.php
@@ -7,17 +7,27 @@
 
 namespace Drupal\Core\Executable;
 
-use Drupal\Component\Plugin\PluginInspectionInterface;
-use Drupal\Core\Processor\ProcessorManager;
+use Drupal\Component\Plugin\ContextAwarePluginInterface;
 use Drupal\Core\Form\FormInterface;
 
 /**
- * An interface for executable and processable plugins.
+ * An interface for executable plugins.
+ *
+ * Executable plugins are context-aware and configurable. They support the
+ * following keys in their plugin definitions:
+ * - context: An array of context definitions, keyed by context name. Each
+ *   context definition is a typed data definition describing the context. Check
+ *   the typed data definition docs for details.
+ * - configuration: An array of configuration option definitions, keyed by
+ *   option name. Each option definition is a typed data definition describing
+ *   the configuration option. Check the typed data definition docs for details.
+ *
+ * @see \Drupal\Core\TypedData\TypedDataManager::create()
  */
-interface ExecutableInterface extends PluginInspectionInterface, FormInterface {
+interface ExecutableInterface extends ContextAwarePluginInterface, FormInterface {
 
   /**
-   * Executes the action.
+   * Executes the plugin.
    */
   public function execute();
 
@@ -27,7 +37,7 @@ public function execute();
   public function summary();
 
   /**
-   * Sets the manager class for use in certain proxy methods.
+   * Sets the executable manager class.
    *
    * @param \Drupal\Core\Condition\ConditionManager $executableManager
    *   The executable manager.
diff --git a/core/lib/Drupal/Core/Executable/ExecutablePluginBase.php b/core/lib/Drupal/Core/Executable/ExecutablePluginBase.php
index 0920cb7..509b221 100644
--- a/core/lib/Drupal/Core/Executable/ExecutablePluginBase.php
+++ b/core/lib/Drupal/Core/Executable/ExecutablePluginBase.php
@@ -8,14 +8,13 @@
 namespace Drupal\Core\Executable;
 
 use Drupal\Core\Plugin\ContextAwarePluginBase;
-use Drupal\Core\Validation\DrupalTranslator;
 use Symfony\Component\Validator\Validation;
 use Drupal\Component\Plugin\Exception\PluginException;
 use Drupal\Component\Plugin\Discovery\DiscoveryInterface;
 use Drupal\Core\Plugin\Context\Context;
 
 /**
- * Provides the basic architecture for executable and processable plugins.
+ * Provides the basic architecture for executable plugins.
  */
 abstract class ExecutablePluginBase extends ContextAwarePluginBase implements ExecutableInterface {
 
@@ -31,6 +30,12 @@
    *
    * Overrides the construction of executable plugins to allow for unvalidated
    * constructor based injection of contexts.
+   *
+   * @param array $configuration
+   *   The plugin configuration, i.e. an array with configuration values keyed
+   *   by configuration option name. The special key 'context' may be used to
+   *   initialize the defined contexts by setting it to an array of context
+   *   values keyed by context names.
    */
   public function __construct(array $configuration, $plugin_id, DiscoveryInterface $discovery) {
     $context = array();
@@ -54,6 +59,15 @@ public function setExecutableManager(ExecutableManagerInterface $executableManag
     return $this;
   }
 
+  /**
+   * Gets an array of definitions of available configuration options.
+   *
+   * @todo: This needs to go into an interface.
+   *
+   * @return array
+   *   An array of typed data definitions describing available configuration
+   *   options, keyed by option name.
+   */
   public function getConfigDefinitions() {
     $definition = $this->getDefinition();
     if (!empty($definition['configuration'])) {
@@ -62,58 +76,63 @@ public function getConfigDefinitions() {
     return array();
   }
 
+  /**
+   * Gets the definition of a configuration option.
+   *
+   * @todo: This needs to go into an interface.
+   *
+   * @return array
+   *   The typed data definition describing the configuration option, or FALSE
+   *   if the option does not exist.
+   */
   public function getConfigDefinition($key) {
     $definition = $this->getDefinition();
     if (!empty($definition['configuration'][$key])) {
       return $definition['configuration'][$key];
     }
-    return NULL;
+    return FALSE;
   }
 
   /**
    * Gets all configuration values.
    *
+   * @todo: This needs to go into an interface.
+   *
    * @see \Drupal\Component\Plugin\PluginBase::$configuration
    *
    * @return array
+   *   The array of all configuration values, keyed by configuration option
+   *   name.
    */
   public function getConfig() {
     return $this->configuration;
   }
 
   /**
-   * Sets a particular value in the block settings.
+   * Sets the value of a particular configuration option.
    *
-   * @param string $key
-   *   The key of PluginBase::$configuration to set.
+   * @param string $name
+   *   The name of the configuration option to set.
    * @param mixed $value
-   *   The value to set for the provided key.
+   *   The value to set.
    *
    * @todo This doesn't belong here. Move this into a new base class in
    *   http://drupal.org/node/1764380.
    * @todo This does not set a value in config(), so the name is confusing.
    *
-   * @see \Drupal\Component\Plugin\PluginBase::$configuration
+   * @return \Drupal\Core\Executable\ExecutablePluginBase.
+   *   The executable object for chaining.
    */
   public function setConfig($key, $value) {
-    $definition = $this->getConfigDefinition($key);
-    if (!is_null($definition)) {
+    if ($definition = $this->getConfigDefinition($key)) {
       $typed_data = typed_data()->create($definition, $value);
-      $validator = Validation::createValidatorBuilder()
-        ->setTranslator(new DrupalTranslator())
-        ->getValidator();
-      if ($validator->validateValue($typed_data, $typed_data->getConstraints())->count() > 0) {
+
+      if ($typed_data->validate()->count() > 0) {
         throw new PluginException("The provided configuration value does not pass validation.");
       }
     }
     $this->configuration[$key] = $value;
     return $this;
   }
-
-  /**
-   * Implements \Drupal\Core\Executable\ExecutableInterface::execute().
-   */
-  abstract public function execute();
-
 }
 
diff --git a/core/lib/Drupal/Core/Plugin/ContextAwarePluginBase.php b/core/lib/Drupal/Core/Plugin/ContextAwarePluginBase.php
index e4daeb1..a67a3c8 100644
--- a/core/lib/Drupal/Core/Plugin/ContextAwarePluginBase.php
+++ b/core/lib/Drupal/Core/Plugin/ContextAwarePluginBase.php
@@ -23,13 +23,14 @@
   /**
    * Override of \Drupal\Component\Plugin\ContextAwarePluginBase::setContextValue().
    */
-  public function setContextValue($key, $value) {
-    $context_definition = $this->getContextDefinition($key);
-    $this->context[$key] = new Context($context_definition);
-    $this->context[$key]->setContextValue($value);
+  public function setContextValue($name, $value) {
+    $context_definition = $this->getContextDefinition($name);
+    // Use the Drupal specific context class.
+    $this->context[$name] = new Context($context_definition);
+    $this->context[$name]->setContextValue($value);
 
     // Verify the provided value validates.
-    if ($this->context[$key]->validate()->count() > 0) {
+    if ($this->context[$name]->validate()->count() > 0) {
       throw new PluginException("The provided context value does not pass validation.");
     }
     return $this;
diff --git a/core/modules/node/lib/Drupal/node/Plugin/Core/Condition/NodeType.php b/core/modules/node/lib/Drupal/node/Plugin/Core/Condition/NodeType.php
index e7deca2..f6d0b22 100644
--- a/core/modules/node/lib/Drupal/node/Plugin/Core/Condition/NodeType.php
+++ b/core/modules/node/lib/Drupal/node/Plugin/Core/Condition/NodeType.php
@@ -28,7 +28,6 @@
  *   }
  * )
  */
-
 class NodeType extends ConditionPluginBase {
 
   /**
@@ -50,7 +49,7 @@ public function buildForm(array $form, array &$form_state) {
   }
 
   /**
-   * Implements \Drupal\condition\ConditionInterface::validate().
+   * Implements \Drupal\Core\Form\FormInterface::validateForm().
    */
   public function validateForm(array &$form, array &$form_state) {
     foreach ($form_state['values']['bundles'] as $bundle) {
@@ -61,7 +60,7 @@ public function validateForm(array &$form, array &$form_state) {
   }
 
   /**
-   * Implements \Drupal\condition\ConditionInterface::submit().
+   * Implements \Drupal\Core\Form\FormInterface::submitForm().
    */
   public function submitForm(array &$form, array &$form_state) {
     $this->configuration['bundles'] = $form_state['values']['bundles'];
@@ -69,7 +68,7 @@ public function submitForm(array &$form, array &$form_state) {
   }
 
   /**
-   * Implements \Drupal\condition\ConditionInterface::summary().
+   * Implements \Drupal\Core\Executable\ExecutableInterface::summary().
    */
   public function summary() {
     if (count($this->configuration['bundles']) > 1) {
diff --git a/core/modules/system/lib/Drupal/system/Tests/Condition/ConditionFormTest.php b/core/modules/system/lib/Drupal/system/Tests/Condition/ConditionFormTest.php
index f28b3c4..b76aac1 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Condition/ConditionFormTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Condition/ConditionFormTest.php
@@ -9,6 +9,13 @@
 
 use Drupal\simpletest\WebTestBase;
 
+/**
+ * Tests condition forms, configuration and execution.
+ *
+ * Checks condition forms and submission and gives a very cursory check to make
+ * sure the configuration that was submitted actually causes the condition to
+ * validate correctly.
+ */
 class ConditionFormTest extends WebTestBase {
 
   public static $modules = array('node', 'condition_test');
@@ -22,7 +29,7 @@ public static function getInfo() {
   }
 
   /**
-   * Submit the system_config_form ensure the configuration has expected values.
+   * Submit the condition_node_type_test_form to test condition forms.
    */
   function testConfigForm() {
     $this->drupalGet('condition_test');
diff --git a/core/modules/system/tests/modules/condition_test/condition_test.module b/core/modules/system/tests/modules/condition_test/condition_test.module
index 76fccd8..1310b21 100644
--- a/core/modules/system/tests/modules/condition_test/condition_test.module
+++ b/core/modules/system/tests/modules/condition_test/condition_test.module
@@ -1,5 +1,8 @@
 <?php
 
+/**
+ * Implements hook_node_info().
+ */
 function condition_test_node_info() {
   return array(
     'article' => array(
diff --git a/core/modules/system/tests/modules/condition_test/lib/Drupal/condition_test/FormController.php b/core/modules/system/tests/modules/condition_test/lib/Drupal/condition_test/FormController.php
index 2d63e19..cd47c89 100644
--- a/core/modules/system/tests/modules/condition_test/lib/Drupal/condition_test/FormController.php
+++ b/core/modules/system/tests/modules/condition_test/lib/Drupal/condition_test/FormController.php
@@ -15,18 +15,32 @@
  */
 class FormController implements FormInterface {
 
+  /**
+   * The condition plugin we will be working with.
+   *
+   * @var \Drupal\Core\Condition\ConditionInterface
+   */
   protected $condition;
 
+  /**
+   * Implements \Drupal\Core\Form\FormInterface::getFormID().
+   */
   public function getFormID() {
     return 'condition_node_type_test_form';
   }
 
+  /**
+   * Provides a simple method the router can fire in order to invoke this form.
+   */
   public function getForm() {
     $manager = new ConditionManager();
     $this->condition = $manager->createInstance('node_type');
     return drupal_get_form($this);
   }
 
+  /**
+   * Implements \Drupal\Core\Form\FormInterface::buildForm().
+   */
   public function buildForm(array $form, array &$form_state) {
     $form = $this->condition->buildForm($form, $form_state);
     $form['actions']['submit'] = array(
@@ -36,15 +50,20 @@ public function buildForm(array $form, array &$form_state) {
     return $form;
   }
 
+  /**
+   * Implements \Drupal\Core\Form\FormInterface::validateForm().
+   */
   public function validateForm(array &$form, array &$form_state) {
     $this->condition->validateForm($form, $form_state);
   }
 
+  /**
+   * Implements \Drupal\Core\Form\FormInterface::submitForm().
+   */
   public function submitForm(array &$form, array &$form_state) {
     $this->condition->submitForm($form, $form_state);
     $config = $this->condition->getConfig();
     $bundles = implode(' and ', $config['bundles']);
-    //drupal_set_message('<pre>' . var_export($this->condition->getConfig(), TRUE) . '</pre>');
     drupal_set_message(t('The bundles are @bundles', array('@bundles' => $bundles)));
   }
 }