diff --git a/core/core.services.yml b/core/core.services.yml
index afccb31..4690799 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -308,9 +308,11 @@ services:
     arguments: ['@config.storage', 'config/schema']
   config.typed:
     class: Drupal\Core\Config\TypedConfigManager
-    arguments: ['@config.storage', '@config.storage.schema', '@cache.discovery', '@module_handler']
+    arguments: ['@config.storage', '@config.storage.schema', '@cache.discovery', '@module_handler', '@class_resolver']
     tags:
       - { name: plugin_manager_cache_clear }
+    calls:
+      - [setValidationConstraintManager, ['@validation.constraint']]
   context.handler:
     class: Drupal\Core\Plugin\Context\ContextHandler
     arguments: ['@typed_data_manager']
diff --git a/core/lib/Drupal/Core/Config/Schema/Mapping.php b/core/lib/Drupal/Core/Config/Schema/Mapping.php
index cf02dd4..8646c92 100644
--- a/core/lib/Drupal/Core/Config/Schema/Mapping.php
+++ b/core/lib/Drupal/Core/Config/Schema/Mapping.php
@@ -6,6 +6,7 @@
  */
 
 namespace Drupal\Core\Config\Schema;
+use Drupal\Core\TypedData\ComplexDataInterface;
 
 /**
  * Defines a mapping configuration element.
@@ -20,7 +21,7 @@
  * Read https://www.drupal.org/node/1905070 for more details about configuration
  * schema, types and type resolution.
  */
-class Mapping extends ArrayElement {
+class Mapping extends ArrayElement implements ComplexDataInterface {
 
   /**
    * {@inheritdoc}
@@ -31,4 +32,24 @@ protected function getElementDefinition($key) {
     return $this->buildDataDefinition($definition, $value, $key);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function set($property_name, $value, $notify = TRUE) {
+    $this->value[$property_name] = $value;
+    // @todo notify?
+    return $this;
+  }
+
+  public function getProperties($include_computed = FALSE) {
+    $properties = array();
+    foreach (array_keys($this->value) as $name) {
+      $definition = $this->getElementDefinition($name);
+      if ($include_computed || !$definition->isComputed()) {
+        $properties[$name] = $this->get($name);
+      }
+    }
+    return $properties;
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Config/Schema/Sequence.php b/core/lib/Drupal/Core/Config/Schema/Sequence.php
index 0c0900a..9cf5186 100644
--- a/core/lib/Drupal/Core/Config/Schema/Sequence.php
+++ b/core/lib/Drupal/Core/Config/Schema/Sequence.php
@@ -6,6 +6,7 @@
  */
 
 namespace Drupal\Core\Config\Schema;
+use Drupal\Core\TypedData\ListInterface;
 
 /**
  * Defines a configuration element of type Sequence.
@@ -16,7 +17,7 @@
  * Read https://www.drupal.org/node/1905070 for more details about configuration
  * schema, types and type resolution.
  */
-class Sequence extends ArrayElement {
+class Sequence extends ArrayElement implements ListInterface {
 
   /**
    * {@inheritdoc}
@@ -34,4 +35,79 @@ protected function getElementDefinition($key) {
     return $this->buildDataDefinition($definition, $value, $key);
   }
 
+  public function getItemDefinition() {
+    // @todo.
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function set($index, $value) {
+    $this->value[$index] = $value;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function first() {
+    reset($this->value);
+    return current($this->value);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function appendItem($value = NULL) {
+    $this->value[] = $value;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function removeItem($index) {
+    unset($this->value[$index]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function filter($callback) {
+    return array_filter($this->value, $callback);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function count() {
+    return count($this->value);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function offsetExists($offset) {
+    return isset($this->value[$offset]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function offsetGet($offset) {
+    return $this->get($offset);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function offsetSet($offset, $value) {
+    return $this->set($offset, $value);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function offsetUnset($offset) {
+    unset($this->elements[$offset]);
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Config/TypedConfigManager.php b/core/lib/Drupal/Core/Config/TypedConfigManager.php
index ca0eb50..d5b9f4b 100644
--- a/core/lib/Drupal/Core/Config/TypedConfigManager.php
+++ b/core/lib/Drupal/Core/Config/TypedConfigManager.php
@@ -11,6 +11,7 @@
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\Config\Schema\ConfigSchemaAlterException;
 use Drupal\Core\Config\Schema\ConfigSchemaDiscovery;
+use Drupal\Core\DependencyInjection\ClassResolverInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\TypedData\TypedDataManager;
 
@@ -49,13 +50,18 @@ class TypedConfigManager extends TypedDataManager implements TypedConfigManagerI
    *   The storage object to use for reading schema data
    * @param \Drupal\Core\Cache\CacheBackendInterface $cache
    *   The cache backend to use for caching the definitions.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler.
+   * @param \Drupal\Core\DependencyInjection\ClassResolverInterface $class_resolver
+   *   The class resolver.
    */
-  public function __construct(StorageInterface $configStorage, StorageInterface $schemaStorage, CacheBackendInterface $cache, ModuleHandlerInterface $module_handler) {
+  public function __construct(StorageInterface $configStorage, StorageInterface $schemaStorage, CacheBackendInterface $cache, ModuleHandlerInterface $module_handler, ClassResolverInterface $class_resolver) {
     $this->configStorage = $configStorage;
     $this->schemaStorage = $schemaStorage;
     $this->setCacheBackend($cache, 'typed_config_definitions');
     $this->alterInfo('config_schema_info');
     $this->moduleHandler = $module_handler;
+    $this->classResolver = $class_resolver;
   }
 
   /**
diff --git a/core/lib/Drupal/Core/TypedData/DataDefinition.php b/core/lib/Drupal/Core/TypedData/DataDefinition.php
index 1ef7c49..6e6f461 100644
--- a/core/lib/Drupal/Core/TypedData/DataDefinition.php
+++ b/core/lib/Drupal/Core/TypedData/DataDefinition.php
@@ -6,12 +6,16 @@
  */
 
 namespace Drupal\Core\TypedData;
+use Drupal\Core\DependencyInjection\DependencySerializationTrait;
 
 /**
  * A typed data definition class for defining data based on defined data types.
  */
 class DataDefinition implements DataDefinitionInterface, \ArrayAccess {
 
+  use DependencySerializationTrait;
+  use TypedDataTrait;
+
   /**
    * The array holding values for all definition keys.
    *
@@ -263,7 +267,7 @@ public function setSetting($setting_name, $value) {
    */
   public function getConstraints() {
     $constraints = isset($this->definition['constraints']) ? $this->definition['constraints'] : array();
-    $constraints += \Drupal::typedDataManager()->getDefaultConstraints($this);
+    $constraints += $this->getTypedDataManager()->getDefaultConstraints($this);
     return $constraints;
   }
 
diff --git a/core/lib/Drupal/Core/TypedData/TypedDataManager.php b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
index be5bcd4..d25f7c4 100644
--- a/core/lib/Drupal/Core/TypedData/TypedDataManager.php
+++ b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
@@ -122,7 +122,10 @@ public function createDataDefinition($data_type) {
       throw new \InvalidArgumentException("Invalid data type '$data_type' has been given");
     }
     $class = $type_definition['definition_class'];
-    return $class::createFromDataType($data_type);
+    $data_definition = $class::createFromDataType($data_type);
+    $data_definition->setTypedDataManager($this);
+
+    return $data_definition;
   }
 
   /**
diff --git a/core/modules/system/config/schema/system.schema.yml b/core/modules/system/config/schema/system.schema.yml
index e34d375..15b3a08 100644
--- a/core/modules/system/config/schema/system.schema.yml
+++ b/core/modules/system/config/schema/system.schema.yml
@@ -7,6 +7,8 @@ system.site:
     uuid:
       type: string
       label: 'Site UUID'
+      constraints:
+        NotNull: []
     name:
       type: label
       label: 'Site name'