diff --git a/core/lib/Drupal/Core/Config/DefinitionLookup.php b/core/lib/Drupal/Core/Config/DefinitionLookup.php
new file mode 100644
index 0000000..901a50a
--- /dev/null
+++ b/core/lib/Drupal/Core/Config/DefinitionLookup.php
@@ -0,0 +1,64 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Config\DefinitionLookup.
+ */
+
+namespace Drupal\Core\Config;
+
+use Drupal\Core\Utility\CacheArray;
+use Drupal\Component\Utility\NestedArray;
+use Symfony\Component\Yaml\YAML;
+
+/**
+ * Extends CacheArray to lazy load configuration element definitions.
+ */
+class DefinitionLookup extends CacheArray {
+
+  /**
+   * Parsed MODULE.config-definition.yml files indexed by module.
+   *
+   * @var array
+   */
+  protected $configDefinitions;
+
+  /**
+   * Implements CacheArray::resolveCacheMiss().
+   */
+  protected function resolveCacheMiss($offset) {
+    list($config_name, $config_key) = explode(':', $offset);
+    list($module_name, $remainder) = explode('.', $config_name, 2);
+    if (!isset($this->configDefinitions[$module_name])) {
+      $definition_file = DRUPAL_ROOT . '/' . drupal_get_path('module', $module_name) . '/' . $module_name . '.config-definition.yml';
+      $this->configDefinitions[$module_name] = file_exists($definition_file) ? YAML::parse($definition_file) : array();
+    }
+    $definition = array();
+    foreach ($this->configDefinitions[$module_name] as $config_name_selector => $object_definitions) {
+      if ($this->selectorMatches($config_name_selector, $config_name)) {
+        foreach ($object_definitions as $config_key_selector => $element_definitions) {
+          if ($this->selectorMatches($config_key_selector, $config_key)) {
+            $definition = array_merge($definition, $element_definitions);
+          }
+        }
+      }
+    }
+    $this->storage[$offset] = $definition;
+    $this->persist($offset);
+    return $definition;
+  }
+
+  /**
+   * Returns TRUE if the subject matches the pattern.
+   */
+  protected function selectorMatches($pattern, $subject) {
+    $subject_parts = explode('.', $subject);
+    $pattern_parts = explode('.', $pattern);
+    if (count($subject_parts) == count($pattern_parts)) {
+      $diff = array_diff_assoc($pattern_parts, $subject_parts);
+      $matches = (empty($diff) || (array_unique($diff) === array('%')));
+      return $matches;
+    }
+  }
+
+}
diff --git a/core/lib/Drupal/Core/CoreBundle.php b/core/lib/Drupal/Core/CoreBundle.php
index e1147ac..4f17388 100644
--- a/core/lib/Drupal/Core/CoreBundle.php
+++ b/core/lib/Drupal/Core/CoreBundle.php
@@ -115,6 +115,12 @@ public function build(ContainerBuilder $container) {
       ->setFactoryMethod('getConnection')
       ->addArgument('slave');
     $container->register('typed_data', 'Drupal\Core\TypedData\TypedDataManager');
+
+    // Register the configuration element definition lookup service.
+    $container->register('config.definition_lookup', 'Drupal\Core\Config\DefinitionLookup')
+      ->addArgument('config:definitions')
+      ->addArgument('cache');
+
     // Add the user's storage for temporary, non-cache data.
     $container->register('lock', 'Drupal\Core\Lock\DatabaseLockBackend');
     $container->register('user.tempstore', 'Drupal\user\TempStoreFactory')
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigDefinitionTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigDefinitionTest.php
new file mode 100644
index 0000000..c661758
--- /dev/null
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigDefinitionTest.php
@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\config\Tests\ConfigDefinitionTest.
+ */
+
+namespace Drupal\config\Tests;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Tests getting definitions of configuration elements.
+ */
+class ConfigDefinitionTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array();
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Configuration definitions',
+      'description' => 'Tests getting definitions of configuration elements.',
+      'group' => 'Configuration',
+    );
+  }
+
+  /**
+   * Tests getting definitions of configuration elements.
+   */
+  function testLookup() {
+    $lookup = drupal_container()->get('config.definition_lookup');
+    $this->assertEqual($lookup['system.site:page.front'], array('label' => 'Default front page'));
+  }
+
+}
diff --git a/core/modules/contact/contact.config-definition.yml b/core/modules/contact/contact.config-definition.yml
new file mode 100644
index 0000000..fb82747
--- /dev/null
+++ b/core/modules/contact/contact.config-definition.yml
@@ -0,0 +1,15 @@
+contact.category.%:
+  id:
+    label: 'Id'
+  label:
+    label: 'Label'
+    translatable: true
+  recipients:
+    label: 'Recipients'
+    translatable: true
+  reply:
+    label: 'Reply'
+    translatable: true
+  weight:
+    type: integer
+    label: 'Weight'
diff --git a/core/modules/image/image.config-definition.yml b/core/modules/image/image.config-definition.yml
new file mode 100644
index 0000000..c13be1a
--- /dev/null
+++ b/core/modules/image/image.config-definition.yml
@@ -0,0 +1,66 @@
+image.style.%:
+  name:
+    label: 'Machine name'
+  label:
+    label: 'Label'
+    translatable: true
+  effects:
+    label: 'Style effects'
+  effects.%:
+    label: 'Image effect'
+  effects.%.weight:
+    type: integer
+    label: 'Weight'
+  effects.%.ieid:
+    label: 'IEID'
+  effects.%.name:
+    label: 'Machine name'
+  effects.%.data:
+    label: 'Data'
+    include: 'image.effect.[%parent.name]'
+
+image.effect.image_crop:
+  width:
+    type: integer
+    label: 'Width'
+  height:
+    type: integer
+    label: 'Height'
+  anchor:
+    label: 'Anchor'
+
+image.effect.image_resize:
+  width:
+    type: integer
+    label: 'Width'
+  height:
+    type: integer
+    label: 'Height'
+
+image.effect.image_rotate:
+  degrees:
+    label: 'Rotation angle'
+  bgcolor:
+    label: 'Background color'
+  random:
+    type: boolean
+    label: 'Randomize'
+
+image.effect.scale:
+  width:
+    type: integer
+    label: 'Width'
+  height:
+    type: integer
+    label: 'Height'
+  upscale:
+    type: boolean
+    label: 'Upscale'
+
+image.effect.scale_and_crop:
+  width:
+    type: integer
+    label: 'Width'
+  height:
+    type: integer
+    label: 'Height'
diff --git a/core/modules/system/system.config-definition.yml b/core/modules/system/system.config-definition.yml
new file mode 100644
index 0000000..3b3bf2f
--- /dev/null
+++ b/core/modules/system/system.config-definition.yml
@@ -0,0 +1,25 @@
+system.site:
+  name:
+    label: 'Site name'
+    translatable: true
+  mail:
+    label: 'Site mail'
+  slogan:
+    label: 'Site slogan'
+    translatable: true
+  page:
+    label: 'Default pages'
+  page.403:
+    label: 'Default 403 (access denied) page'
+  page.404:
+    label: 'Default 404 (not found) page'
+  page.front:
+    label: 'Default front page'
+
+system.maintenance:
+  enabled:
+    type: boolean
+    label: 'Put site into maintenance mode'
+  message:
+    label: 'Message to display when in maintenance mode'
+    translatable: true
diff --git a/core/modules/user/user.config-definition.yml b/core/modules/user/user.config-definition.yml
new file mode 100644
index 0000000..2c7a631
--- /dev/null
+++ b/core/modules/user/user.config-definition.yml
@@ -0,0 +1,11 @@
+user.mail:
+  "":
+    label: 'User mails'
+  %:
+    label: 'Mail text'
+  %.subject:
+    label: 'Subject'
+    translatable: true
+  %.body:
+    label: 'Body'
+    translatable: true