diff --git a/core/includes/config.inc b/core/includes/config.inc
index 99774ef..5e51f65 100644
--- a/core/includes/config.inc
+++ b/core/includes/config.inc
@@ -174,10 +174,18 @@ function config_sync_get_changes(StorageInterface $source_storage, StorageInterf
  * Retrieves metadata for a configuration object or key.
  *
  * The metadata has the same structure as the configuration object itself but
- * the configuration values are replaced by an array containing exactly one
- * element. The key is .definition and the value is a $definition array to
- * be passed to typed_data()->create() or
- * \Drupal\Core\TypedData\TypedDataManager::create().
+ * the configuration values are replaced by an array containing some special
+ * elements, whose keys are prefixed by a dot:
+ * - '.definition', array containing the data type definition of the element.
+ *   The value is a $definition array to be passed to typed_data()->create()
+ *   or \Drupal\Core\TypedData\TypedDataManager::create().
+ * - '.include', name of additional metadata file to be added. The current
+ *   metadata will then be merged on top of it using
+ *   NestedArray::mergeRecursive()
+ * - '.list', contains an array of metadata to be used for each of the children
+ *   elements when there's no other metadata for them. This will also imply
+ *   that the type definition's 'list' property for the parent element will be
+ *   set to TRUE.
  *
  * For example, for the config file core/modules/system/config/system.site.yml:
  * @code
@@ -239,26 +247,24 @@ function config_sync_get_changes(StorageInterface $source_storage, StorageInterf
  * @code
  *   .definition:
  *     label: 'User mails'
- *     list: '1'
- *     list settings:
- *       elements name: 'user.mail.%'
- * @endcode
- *
- * For every element, meta/user.mail.%.yml is read as specified by the
- * 'elements name' list settings:
- * @code
- *   .definition:
- *     label: 'Mail text'
- *   subject:
+ *   .list:
  *     .definition:
- *       label: 'Subject'
- *       type: 'text'
- *   body:
- *     .definition:
- *       label: 'Body'
- *       type: 'text'
+ *       label: 'Mail text'
+ *     subject:
+ *       .definition:
+ *         label: 'Subject'
+ *         type: 'text'
+ *     body:
+ *       .definition:
+ *         label: 'Body'
+ *         type: 'text'
+
  * @endcode
  *
+ * For every element in the list of user mails, the metadata is specified by
+ * the '.list' key which contains an array of metadata to be used for each of
+ * the nested configuration elements.
+ *
  * As said above, the type for list elements is config_element, so the
  * $definition array for the status_blocked array is:
  * @code
@@ -268,6 +274,14 @@ function config_sync_get_changes(StorageInterface $source_storage, StorageInterf
  *   );
  * @endcode
  *
+ * While the $definition array for the 'subject' nested property of it is:
+ * @code
+ *   array(
+ *     'label' => 'Subject',
+ *     'type' => 'text',
+ *   );
+ * @endcode
+ *
  * The % in meta/user.mail.%.yml is a placeholder and the array key can be
  * used for more specific metadata. So, meta/user.mail.status_canceled.yml
  * could be used to specify some metadata only for the status_canceled list
@@ -275,8 +289,8 @@ function config_sync_get_changes(StorageInterface $source_storage, StorageInterf
  * in meta/user.mail.%.yml as described in
  * \Drupal\Component\Utility\NestedArray::mergeDeep().
  *
- * Other lists use a property inside a list element for this key. For example,
- * core/modules/image/config/image.style.medium.yml:
+ * Other lists use a property inside a the '.include' element for this key.
+ * For example, core/modules/image/config/image.style.medium.yml:
  * @code
  *   name: medium
  *   label: Medium (220x220)
@@ -304,20 +318,62 @@ function config_sync_get_changes(StorageInterface $source_storage, StorageInterf
  *   effects:
  *     .definition:
  *       label: 'Style effects'
- *       list: '1'
- *       list settings:
- *         elements name: 'image.style.effects.%'
- *         elements key: 'name'
+ *     .list:
+ *       .include: 'image.effect.[name]'
+ *       .definition:
+ *         label: 'Image style effect'
+ *       weight:
+ *         .definition:
+ *           label: 'Weight'
+ *           type: integer
+ *       ieid:
+ *         .definition:
+ *           label: 'IEID'
  * @endcode
  *
+ * For this example, for each image effect, we have the metadata under the
+ * '.list' key. Each of the effects will have:
+ * - Some common properties that depend on the image style (weight, ieid) and
+ *   since they are specific of image styles (not image effects) they are
+ *   defined right in this element.
+ * - Some common properties for all image effects that are defined in
+ *   image.effect.%.yml
+ * - Some properties specific of a given image effect, like the ones in
+ *   image.effect.image_scale.yml
+ *
  * In this case we want to reuse the metadata for 'image_scale' every time
- * that effect is used. So the elements key is set to name, which in this
+ * that effect is used. So the '[name]' variable in the include is replaced
+ * by the element's 'name' value, which in this
  * example will indeed be 'image_scale' so to find the metadata for the
  * bddf0d06-42f9-4c75-a700-a33cafa25ea0 list element,
- * meta/image.style.effects.image_scale.yml is used if it exists and
- * meta/image.style.effects.%.yml if it does not.
+ * meta/image.effect.image_scale.yml is used if it exists and
+ * meta/image.effect.%.yml if it does not.
+ *
+ * For example here is meta/image.effect.image_scale.yml:
+ * @code
+ *   .include: 'image.effect.%'
+ *   .definition:
+ *     label: 'Image scale'
+ *   data:
+ *     width:
+ *       .definition:
+ *         label: 'Width'
+ *         type: 'integer'
+ *     height:
+ *       .definition:
+ *         label: 'Height'
+ *         type: 'integer'
+ *     upscale:
+ *       .definition:
+ *         label: 'Upscale'
+ *         type: 'boolean'
+ * @endcode
  *
- * For example here is meta/image.style.effects.%.yml:
+ * Note there is another '.include' at the top of the file which means that
+ * file is included first and then this one adds or overrides properties in
+ * image.effect.%.yml
+ *
+ * And here is meta/image.effect.%.yml:
  * @code
  *   .definition:
  *     label: 'Image style effect'
@@ -336,27 +392,11 @@ function config_sync_get_changes(StorageInterface $source_storage, StorageInterf
  *     .definition:
  *       label: 'IEID'
  * @endcode
- * And meta/image.style.effects.image_scale.yml:
- * @code
- *   .definition:
- *     label: 'Image scale'
- *   data:
- *     width:
- *       .definition:
- *         label: 'Width'
- *         type: 'integer'
- *     height:
- *       .definition:
- *         label: 'Height'
- *         type: 'integer'
- *     upscale:
- *       .definition:
- *         label: 'Upscale'
- *         type: 'boolean'
- * @endcode
+ *
+
  *
  * In this example, it's visible how the top-level label is overridden in
- * meta/image.style.effects.image_scale.yml.
+ * meta/image.effect.image_scale.yml.
  *
  * @see \Drupal\Core\TypedData\TypedDataManager::create()
  * @see \Drupal\Core\Config\Metadata\ElementBase
diff --git a/core/lib/Drupal/Core/Config/Metadata/ElementBase.php b/core/lib/Drupal/Core/Config/Metadata/ElementBase.php
index 81b75cd..3f8e68d 100644
--- a/core/lib/Drupal/Core/Config/Metadata/ElementBase.php
+++ b/core/lib/Drupal/Core/Config/Metadata/ElementBase.php
@@ -7,8 +7,10 @@
 
 namespace Drupal\Core\Config\Metadata;
 
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\TypedData\TypedDataInterface;
 use Drupal\Core\TypedData\Type\TypedData;
+
 use ArrayIterator;
 use IteratorAggregate;
 
@@ -78,25 +80,15 @@ protected function getElement($key) {
    */
   protected function getElementMetadata($key) {
     // Metadata for nested elements must be built before.
-    if (!isset($this->metadata[$key])) {
-      $this->metadata[$key] = $this->buildElementMetadata($key, $this->value[$key]);
+    if (isset($this->metadata[$key])) {
+      return $this->metadata[$key];
+    }
+    elseif (isset($this->metadata['.list'])) {
+      return $this->metadata['.list'];
+    }
+    else {
+      return array();
     }
-    return $this->metadata[$key];
-  }
-
-  /**
-   * Builds metadata for a child element.
-   *
-   * @param string $key
-   *   Element's key.
-   * @param mixed $data
-   *   Configuration data for the element.
-   *
-   * @return array
-   *   Configuration metadata for the element.
-   */
-  protected function buildElementMetadata($key, $data) {
-    return isset($this->metadata[$key]) ? $this->metadata[$key] : array();
   }
 
   /**
@@ -149,6 +141,22 @@ public function getMetadata() {
    * Implements Drupal\Core\Config\Metadata\ElementInterface::setMetadata().
    */
   public function setMetadata($metadata) {
+    // Process '.include' directive if present.
+    if (isset($metadata['.include'])) {
+      $replace = array();
+      // If this element has a key (is not the parent), add it to the variables
+      // for replacement under '[%key]'
+      if (isset($this->key)) {
+        $replace['[%key]'] = $this->key;
+      }
+       // Get other variable replacements from the data, only scalar values.
+      if (is_array($this->value)) {
+        foreach (array_filter($this->value, 'is_scalar') as $key => $value) {
+          $replace['[' . $key . ']'] = $value;
+        }
+      }
+      $metadata = $this->processInclude($metadata, $replace);
+    }
     $this->metadata = $metadata;
   }
 
@@ -277,10 +285,13 @@ public static function buildElement($value, $metadata, $key, $parent = NULL) {
    */
   public static function buildDefinition($data, $metadata) {
     $definition = isset($metadata['.definition']) ? $metadata['.definition'] : array();
-    unset($metadata['.definition']);
-    // The default type will depend on whether we've got children or not.
+    // If we have a '.list' directive we assume this is a list.
+    if (isset($metadata['.list'])) {
+      $definition += array('list' => TRUE);
+    }
+    // The default type will depend on whether data is an array.
     if (!isset($definition['type'])) {
-      if (!empty($metadata) || is_array($data) || !empty($definition['list']) || !empty($definition['list settings'])) {
+      if (is_array($data) || !empty($definition['list']) || !empty($definition['list settings'])) {
         $definition['type'] = 'config_element';
       }
       else {
@@ -290,4 +301,24 @@ public static function buildDefinition($data, $metadata) {
     return $definition;
   }
 
+  /**
+   * Processes '.include' keyword applying variable replacements.
+   *
+   * This method is called recursively in case the included metadata has also
+   * an '.include' keyword.
+   *
+   * @param array $metadata
+   *   Metadata array for the element.
+   * @param array $replace
+   *   Variable replacements for the include value.
+   */
+  protected function processInclude($metadata, $replace) {
+    if (isset($metadata['.include']) && $include = config_metadata(strtr($metadata['.include'], $replace))) {
+      // There may be nested '.include' directives, we need to process them too.
+      $include = $this->processInclude($include, $replace);
+      $metadata = NestedArray::mergeDeep($include, $metadata);
+    }
+    return $metadata;
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Config/Metadata/ListElement.php b/core/lib/Drupal/Core/Config/Metadata/ListElement.php
index 659628c..4cb494d 100644
--- a/core/lib/Drupal/Core/Config/Metadata/ListElement.php
+++ b/core/lib/Drupal/Core/Config/Metadata/ListElement.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\Core\Config\Metadata;
 
-use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\TypedData\ListInterface;
 
 /**
@@ -15,52 +14,8 @@
  *
  * This is a configuration element that wraps a list of nested elements in the
  * configuration data.
- *
- * Supported list settings (below the definition's 'list settings' key) are:
- * - 'elements name', Configuration name for each of the nested elements, may
- *   contain the placeholder '%' to replace by the element's key.
- * - 'elements key', Name of the configuration data property to be used as the
- *   key for name replacement.
  */
 class ListElement extends ElementBase implements ListInterface {
-
-  /**
-   * Overrides Drupal\Core\Config\Metadata\ElementBase::buildElementMetadata().
-   */
-  protected function buildElementMetadata($key, $data) {
-    $meta = parent::buildElementMetadata($key, $data);
-    // When the parent element is a list, elements may have special settings.
-    if (isset($this->definition['list settings'])) {
-      $settings = $this->definition['list settings'];
-      if (isset($settings['elements_base']) && $base = config_metadata($settings['elements_base'])) {
-        // Load common base metadata for all elements.
-        $meta = NestedArray::mergeDeep($base, $meta);
-      }
-      if (isset($settings['elements name'])) {
-        // Load specific metadata for each element.
-        $name = $settings['elements name'];
-        $element_key = $key;
-        if (isset($settings['elements key'])) {
-          // The search key for this one is in the data itself.
-          $element_key = isset($data[$settings['elements key']]) ? $data[$settings['elements key']] : NULL;
-        }
-        if ($element_key) {
-          $name = str_replace('%', $element_key, $name);
-        }
-        if ($merge = config_metadata($name)) {
-          $meta = NestedArray::mergeDeep($meta, $merge);
-        }
-      }
-      if (isset($settings['elements_label']) && !isset($meta['.label'])) {
-        // Extract element's label from configuration data.
-        if (!empty($data[$settings['elements_label']])) {
-          $meta['.label'] = $data[$settings['elements_label']];
-        }
-      }
-    }
-    return $meta;
-  }
-
   /**
    * Implements Drupal\Core\TypedData\ListInterface::isEmpty().
    */
diff --git a/core/lib/Drupal/Core/Config/Metadata/MetadataLookup.php b/core/lib/Drupal/Core/Config/Metadata/MetadataLookup.php
index 529ecb0..779005b 100644
--- a/core/lib/Drupal/Core/Config/Metadata/MetadataLookup.php
+++ b/core/lib/Drupal/Core/Config/Metadata/MetadataLookup.php
@@ -54,20 +54,17 @@ public function __construct(MetadataStorage $metadata_storage) {
    * Overrides DrupalCacheArray::resolveCacheMiss().
    */
   protected function resolveCacheMiss($offset) {
-    $metadata = array();
-    // First read the base data.
-    if (($base_name = $this->getBaseName($offset)) && ($base_data = $this->offsetGet($base_name))) {
-      $metadata = $base_data;
+    $metadata = $this->metadataStorage->read($offset);
+    // If no metadata with this exact name, try the fallback name.
+    if ($metadata === FALSE && ($basename = $this->getFallbackName($offset))) {
+      $metadata = $this->offsetGet($basename);
     }
-    if ($override = $this->metadataStorage->read($offset)) {
-      $metadata = NestedArray::mergeDeep($metadata, $override);
-    }
-    $this->storage[$offset] = $metadata;
+    $this->storage[$offset] = $metadata ? $metadata : array();
     return $this->storage[$offset];
   }
 
   /**
-   * Gets base metadata name.
+   * Gets fallback metadata name.
    *
    * @param string $name
    *   Configuration name or key.
@@ -75,7 +72,7 @@ protected function resolveCacheMiss($offset) {
    * @return string
    *   Same name with the last part replaced by the filesystem marker.
    */
-  protected static function getBaseName($name) {
+  protected static function getFallbackName($name) {
     $replaced = preg_replace('/\.[^.]+$/', '.' . self::BASE_MARK, $name);
     if ($replaced != $name) {
       return $replaced;
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigMetadataTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigMetadataTest.php
index 947603a..1807505 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigMetadataTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigMetadataTest.php
@@ -51,7 +51,6 @@ function testBasicMetadata() {
     $expected = array();
     $expected['name']['.definition'] = array(
       'label' => 'Machine name',
-      'type' => 'string',
     );
     $expected['label']['.definition'] = array(
       'label' => 'Label',
@@ -59,13 +58,42 @@ function testBasicMetadata() {
     );
     $expected['effects']['.definition'] = array(
       'label' =>  'Style effects',
-      'list' => '1',
-      'list settings' => array(
-        'elements name' => 'image.style.effects.%',
-        'elements key' => 'name'
-      ),
+    );
+    $expected['effects']['.list']['.include'] = 'image.effect.[name]';
+    $expected['effects']['.list']['weight']['.definition'] = array(
+      'label' => 'Weight',
+      'type' => 'integer'
+    );
+    $expected['effects']['.list']['ieid']['.definition'] = array(
+      'label' => 'IEID'
     );
     $this->assertEqual($metadata, $expected, 'Retrieved the right metadata for image.style.large');
+
+    // Most complex case, metadata from actual configuration element using includes.
+    $metadata = config_wrapper('image.style.medium')->get('effects.bddf0d06-42f9-4c75-a700-a33cafa25ea0')->getMetadata();
+    $expected = array();
+    $expected['.include'] = 'image.effect.[name]';
+    $expected['.definition']['label'] = 'Image scale';
+    $expected['data']['width']['.definition'] = array(
+      'label' => 'Width',
+      'type' => 'integer',
+    );
+    $expected['data']['height']['.definition'] = array(
+      'label' => 'Height',
+      'type' => 'integer',
+    );
+    $expected['data']['upscale']['.definition'] = array(
+      'label' => 'Upscale',
+      'type' => 'boolean',
+    );
+    $expected['weight']['.definition'] = array(
+      'label' => 'Weight',
+      'type' => 'integer'
+    );
+    $expected['ieid']['.definition'] = array(
+      'label' => 'IEID'
+    );
+    $this->assertEqual($metadata, $expected, 'Retrieved the right metadata for the first effect of image.style.medium');
   }
 
   /**
diff --git a/core/modules/contact/meta/contact.category.%.yml b/core/modules/contact/meta/contact.category.%.yml
index 6a772e3..3e6b077 100644
--- a/core/modules/contact/meta/contact.category.%.yml
+++ b/core/modules/contact/meta/contact.category.%.yml
@@ -1,9 +1,5 @@
-.definition:
-  settings:
-    label: label
 id:
   .definition:
-    type: string
     label: 'Id'
 label:
   .definition:
@@ -11,7 +7,6 @@ label:
     label: 'Label'
 recipients:
   .definition:
-    list: '1'
     label: 'Recipients'
 reply:
   .definition:
diff --git a/core/modules/image/meta/image.effect.%.yml b/core/modules/image/meta/image.effect.%.yml
new file mode 100644
index 0000000..cc6bddc
--- /dev/null
+++ b/core/modules/image/meta/image.effect.%.yml
@@ -0,0 +1,8 @@
+.definition:
+  label: 'Image effect'
+name:
+  .definition:
+    label: 'Machine name'
+data:
+  .definition:
+    label: 'Data'
diff --git a/core/modules/image/meta/image.effect.image_scale.yml b/core/modules/image/meta/image.effect.image_scale.yml
new file mode 100644
index 0000000..c17c55d
--- /dev/null
+++ b/core/modules/image/meta/image.effect.image_scale.yml
@@ -0,0 +1,16 @@
+.include: image.effect.%.yml
+.definition:
+  label: 'Image scale'
+data:
+  width:
+    .definition:
+      label: 'Width'
+      type: integer
+  height:
+    .definition:
+      label: 'Height'
+      type: integer
+  upscale:
+    .definition:
+      label: 'Upscale'
+      type: boolean
diff --git a/core/modules/image/meta/image.style.%.yml b/core/modules/image/meta/image.style.%.yml
index 6975590..31852b8 100644
--- a/core/modules/image/meta/image.style.%.yml
+++ b/core/modules/image/meta/image.style.%.yml
@@ -1,7 +1,6 @@
 name:
   .definition:
     label: 'Machine name'
-    type: string
 label:
   .definition:
     label: 'Label'
@@ -9,7 +8,12 @@ label:
 effects:
   .definition:
     label: 'Style effects'
-    list: '1'
-    list settings:
-      elements name: 'image.style.effects.%'
-      elements key: 'name'
+  .list:
+    .include: 'image.effect.[name]'
+    weight:
+      .definition:
+        label: 'Weight'
+        type: integer
+    ieid:
+      .definition:
+        label: 'IEID'
\ No newline at end of file
diff --git a/core/modules/image/meta/image.style.effects.%.yml b/core/modules/image/meta/image.style.effects.%.yml
deleted file mode 100644
index c0d4e95..0000000
--- a/core/modules/image/meta/image.style.effects.%.yml
+++ /dev/null
@@ -1,16 +0,0 @@
-.definition:
-  label: 'Image style effect'
-name:
-  .definition:
-    label: 'Machine name'
-    type: string
-data:
-  .definition:
-    label: 'Data'
-weight:
-  .definition:
-    label: 'Weight'
-    type: integer
-ieid:
-  .definition:
-    label: 'IEID'
diff --git a/core/modules/image/meta/image.style.effects.image_scale.yml b/core/modules/image/meta/image.style.effects.image_scale.yml
deleted file mode 100644
index 7f893bf..0000000
--- a/core/modules/image/meta/image.style.effects.image_scale.yml
+++ /dev/null
@@ -1,15 +0,0 @@
-.definition:
-  label: 'Image scale'
-data:
-  width:
-    .definition:
-      label: 'Width'
-      type: 'integer'
-  height:
-    .definition:
-      label: 'Height'
-      type: 'integer'
-  upscale:
-    .definition:
-      label: 'Upscale'
-      type: 'boolean'
diff --git a/core/modules/locale/lib/Drupal/locale/LocaleTypedConfig.php b/core/modules/locale/lib/Drupal/locale/LocaleTypedConfig.php
index 6108a74..1e72c64 100644
--- a/core/modules/locale/lib/Drupal/locale/LocaleTypedConfig.php
+++ b/core/modules/locale/lib/Drupal/locale/LocaleTypedConfig.php
@@ -179,8 +179,10 @@ protected function getTranslatedData($elements, $options) {
    * Translates element if it fits our translation criteria.
    *
    * For an element to be translatable by locale module it needs to be of type
-   * 'text'. Translatable elements may define the string context by using the
-   * 'locale context' key under the element definition's 'constraints'.
+   * 'text'. Translatable elements may use these additional keys in their data
+   * definition:
+   * - 'translatable', FALSE to opt out of translation.
+   * - 'locale context', to define the string context.
    *
    * @param \Drupal\Core\TypedData\TypedDataInterface $element
    *   Configuration element.
@@ -194,8 +196,8 @@ public function translateElement($element, $options) {
     if ($this->canTranslate($options['source'], $options['target'])) {
       $definition = $element->getDefinition();
       $value = $element->getValue();
-      if ($value && is_string($value) && $element->getType() == 'text') {
-        $context = isset($definition['constraints']['locale context']) ? $definition['constraints']['locale context'] : '';
+      if ($value && is_string($value) && $element->getType() == 'text' && (!isset($definition['translatable']) || $definition['translatable'])) {
+        $context = isset($definition['locale context']) ? $definition['locale context'] : '';
         if ($translation = $this->translateString($options['target'], $value, $context)) {
           $element->setValue($translation);
           return TRUE;
diff --git a/core/modules/user/meta/user.mail.%.yml b/core/modules/user/meta/user.mail.%.yml
deleted file mode 100644
index 36ee7f3..0000000
--- a/core/modules/user/meta/user.mail.%.yml
+++ /dev/null
@@ -1,10 +0,0 @@
-.definition:
-  label: 'Mail text'
-subject:
-  .definition:
-    label: 'Subject'
-    type: 'text'
-body:
-  .definition:
-    label: 'Body'
-    type: 'text'
diff --git a/core/modules/user/meta/user.mail.yml b/core/modules/user/meta/user.mail.yml
index 91e9030..cd710a9 100644
--- a/core/modules/user/meta/user.mail.yml
+++ b/core/modules/user/meta/user.mail.yml
@@ -1,5 +1,13 @@
 .definition:
   label: 'User mails'
-  list: '1'
-  list settings:
-    elements name: 'user.mail.%'
+.list:
+  .definition:
+    label: 'Mail text'
+  subject:
+    .definition:
+      label: 'Subject'
+      type: text
+  body:
+    .definition:
+      label: 'Body'
+      type: text
\ No newline at end of file