diff --git a/core/lib/Drupal/Core/CoreBundle.php b/core/lib/Drupal/Core/CoreBundle.php
index 71ef37b..538290e 100644
--- a/core/lib/Drupal/Core/CoreBundle.php
+++ b/core/lib/Drupal/Core/CoreBundle.php
@@ -103,7 +103,10 @@ public function build(ContainerBuilder $container) {
       ->setFactoryClass('Drupal\Core\Database\Database')
       ->setFactoryMethod('getConnection')
       ->addArgument('slave');
-    $container->register('typed_data', 'Drupal\Core\TypedData\TypedDataManager');
+    $container->register('typed_data', 'Drupal\Core\TypedData\TypedDataManager')
+      ->addMethodCall('setValidationConstraintManager', array(new Reference('validation.constraint', ContainerInterface::IGNORE_ON_INVALID_REFERENCE)));
+    $container->register('validation.constraint', 'Drupal\Core\Validation\ConstraintManager');
+
     // 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/lib/Drupal/Core/Entity/Field/FieldItemBase.php b/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
index 5c71aa3..9b51629 100644
--- a/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
+++ b/core/lib/Drupal/Core/Entity/Field/FieldItemBase.php
@@ -121,13 +121,6 @@ public function getString() {
   }
 
   /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // @todo implement
-  }
-
-  /**
    * Implements ComplexDataInterface::get().
    */
   public function get($property_name) {
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/EntityReferenceItem.php b/core/lib/Drupal/Core/Entity/Field/Type/EntityReferenceItem.php
index a60e65e..261bd92 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/EntityReferenceItem.php
@@ -39,6 +39,9 @@ public function getPropertyDefinitions() {
         // @todo: Lookup the entity type's ID data type and use it here.
         'type' => 'integer',
         'label' => t('Entity ID'),
+        'constraints' => array(
+          'Min' => array('limit' => 0),
+        ),
       );
       self::$propertyDefinitions[$entity_type]['entity'] = array(
         'type' => 'entity',
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/EntityTranslation.php b/core/lib/Drupal/Core/Entity/Field/Type/EntityTranslation.php
index 280fca9..4a08987 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/EntityTranslation.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/EntityTranslation.php
@@ -237,11 +237,4 @@ public function access($operation = 'view', \Drupal\user\Plugin\Core\Entity\User
     $method = $operation . 'Access';
     return entity_access_controller($this->parent->entityType())->$method($this->parent, $this->langcode, $account);
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate($value = NULL) {
-    // @todo implement
-  }
 }
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/EntityWrapper.php b/core/lib/Drupal/Core/Entity/Field/Type/EntityWrapper.php
index 97449e7..5607ec4 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/EntityWrapper.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/EntityWrapper.php
@@ -125,13 +125,6 @@ public function getString() {
   }
 
   /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate($value = NULL) {
-    // TODO: Implement validate() method.
-  }
-
-  /**
    * Implements IteratorAggregate::getIterator().
    */
   public function getIterator() {
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/Field.php b/core/lib/Drupal/Core/Entity/Field/Type/Field.php
index cc5951c..9d2448a 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/Field.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/Field.php
@@ -114,10 +114,11 @@ public function getString() {
   }
 
   /**
-   * Implements TypedDataInterface::validate().
+   * Implements TypedDataInterface::getConstraints().
    */
-  public function validate() {
-    // @todo implement
+  public function getConstraints() {
+    // Apply the constraints to the list items only.
+    return array();
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/IntegerItem.php b/core/lib/Drupal/Core/Entity/Field/Type/IntegerItem.php
index 1f4b4e6..728a65f 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/IntegerItem.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/IntegerItem.php
@@ -32,6 +32,11 @@ public function getPropertyDefinitions() {
       self::$propertyDefinitions['value'] = array(
         'type' => 'integer',
         'label' => t('Integer value'),
+        // @todo: Remove this in favor of a 'Type' constraint and move it to the
+        // integer type definition.
+        'constraints' => array(
+          'Min' => array('limit' => 5),
+        ),
       );
     }
     return self::$propertyDefinitions;
diff --git a/core/lib/Drupal/Core/Plugin/Validation/Constraint/EntityTypeConstraint.php b/core/lib/Drupal/Core/Plugin/Validation/Constraint/EntityTypeConstraint.php
new file mode 100644
index 0000000..ca46ee8
--- /dev/null
+++ b/core/lib/Drupal/Core/Plugin/Validation/Constraint/EntityTypeConstraint.php
@@ -0,0 +1,38 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Validation\Constraint\EntityTypeConstraint.
+ */
+
+namespace Drupal\Core\Plugin\Validation\Constraint;
+
+use Symfony\Component\Validator\Constraint;
+use Drupal\Core\Annotation\Plugin;
+use Drupal\Core\Annotation\Translation;
+
+
+/**
+ * Checks if a value is a valid entity type.
+ *
+ * @todo: Implement symfony constraint and constraint validator.
+ *
+ * @Plugin(
+ *   id = "entity type",
+ *   label = @Translation("Entity type constraint", context = "Validation"),
+ *   message = @Translation("The value of %label is not a valid entity type.", context = "Validation"),
+ *   type = "field"
+ * )
+ */
+class EntityTypeConstraint extends Constraint {
+
+  /**
+   * Checks if a value is a valid entity type.
+   *
+   * @return boolean
+   *   TRUE if value is a known entity type, FALSE if the value is empty.
+   */
+  public function validate($value) {
+     return array_key_exists($value, entity_get_info());
+  }
+}
diff --git a/core/lib/Drupal/Core/TypedData/Type/Binary.php b/core/lib/Drupal/Core/TypedData/Type/Binary.php
index 7ec5e6b..609bac8 100644
--- a/core/lib/Drupal/Core/TypedData/Type/Binary.php
+++ b/core/lib/Drupal/Core/TypedData/Type/Binary.php
@@ -74,11 +74,4 @@ public function getString() {
     }
     return $contents;
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // TODO: Implement validate() method.
-  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Type/Boolean.php b/core/lib/Drupal/Core/TypedData/Type/Boolean.php
index 5714599..c31cbcd 100644
--- a/core/lib/Drupal/Core/TypedData/Type/Boolean.php
+++ b/core/lib/Drupal/Core/TypedData/Type/Boolean.php
@@ -30,11 +30,4 @@ class Boolean extends TypedData implements TypedDataInterface {
   public function setValue($value) {
     $this->value = isset($value) ? (bool) $value : $value;
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // TODO: Implement validate() method.
-  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Type/Date.php b/core/lib/Drupal/Core/TypedData/Type/Date.php
index 3c0f3a9..9822b37 100644
--- a/core/lib/Drupal/Core/TypedData/Type/Date.php
+++ b/core/lib/Drupal/Core/TypedData/Type/Date.php
@@ -52,11 +52,4 @@ public function setValue($value) {
   public function getString() {
     return (string) $this->getValue();
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // TODO: Implement validate() method.
-  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Type/Duration.php b/core/lib/Drupal/Core/TypedData/Type/Duration.php
index 9fd8ceb..68093fd 100644
--- a/core/lib/Drupal/Core/TypedData/Type/Duration.php
+++ b/core/lib/Drupal/Core/TypedData/Type/Duration.php
@@ -58,11 +58,4 @@ public function getString() {
     // DateInterval::__construct() and setValue().
     return (string) $this->getValue()->format('%rP%yY%mM%dDT%hH%mM%sS');
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // TODO: Implement validate() method.
-  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Type/Float.php b/core/lib/Drupal/Core/TypedData/Type/Float.php
index 798499c..ec77fa8 100644
--- a/core/lib/Drupal/Core/TypedData/Type/Float.php
+++ b/core/lib/Drupal/Core/TypedData/Type/Float.php
@@ -30,11 +30,4 @@ class Float extends TypedData implements TypedDataInterface {
   public function setValue($value) {
     $this->value = isset($value) ? (float) $value : $value;
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // TODO: Implement validate() method.
-  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Type/Integer.php b/core/lib/Drupal/Core/TypedData/Type/Integer.php
index 4e9b59a..ec21349 100644
--- a/core/lib/Drupal/Core/TypedData/Type/Integer.php
+++ b/core/lib/Drupal/Core/TypedData/Type/Integer.php
@@ -30,11 +30,4 @@ class Integer extends TypedData implements TypedDataInterface {
   public function setValue($value) {
     $this->value = isset($value) ? (int) $value : $value;
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // TODO: Implement validate() method.
-  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Type/Language.php b/core/lib/Drupal/Core/TypedData/Type/Language.php
index 67f4df8..483bbc9 100644
--- a/core/lib/Drupal/Core/TypedData/Type/Language.php
+++ b/core/lib/Drupal/Core/TypedData/Type/Language.php
@@ -124,11 +124,4 @@ public function getString() {
     $language = $this->getValue();
     return $language ? $language->name : '';
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // TODO: Implement validate() method.
-  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Type/String.php b/core/lib/Drupal/Core/TypedData/Type/String.php
index fef3248..b15042b 100644
--- a/core/lib/Drupal/Core/TypedData/Type/String.php
+++ b/core/lib/Drupal/Core/TypedData/Type/String.php
@@ -30,11 +30,4 @@ class String extends TypedData implements TypedDataInterface {
   public function setValue($value) {
     $this->value = isset($value) ? (string) $value : $value;
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // TODO: Implement validate() method.
-  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Type/TypedData.php b/core/lib/Drupal/Core/TypedData/Type/TypedData.php
index 1e70c53..c3ab452 100644
--- a/core/lib/Drupal/Core/TypedData/Type/TypedData.php
+++ b/core/lib/Drupal/Core/TypedData/Type/TypedData.php
@@ -70,4 +70,28 @@ public function setValue($value) {
   public function getString() {
     return (string) $this->getValue();
   }
+
+  /**
+   * Implements TypedDataInterface::getConstraints().
+   */
+  public function getConstraints() {
+    $constraints = array();
+    if (isset($this->definition['constraints'])) {
+      foreach ($this->definition['constraints'] as $name => $options) {
+        // @todo: Add the typed data manager as proper dependency.
+        // @todo: Figure out how to handle nested constraint structures as
+        // collections.
+        $constraints[] = typed_data()->getValidationConstraintManager()->createInstance($name, $options);
+      }
+    }
+    return $constraints;
+  }
+
+  /**
+   * Implements TypedDataInterface::validate().
+   */
+  public function validate() {
+    // @todo: Add the typed data manager as proper dependency.
+    return typed_data()->getValidator()->validate($this);
+  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Type/Uri.php b/core/lib/Drupal/Core/TypedData/Type/Uri.php
index 010fa03..354eed5 100644
--- a/core/lib/Drupal/Core/TypedData/Type/Uri.php
+++ b/core/lib/Drupal/Core/TypedData/Type/Uri.php
@@ -29,11 +29,4 @@ class Uri extends TypedData implements TypedDataInterface {
   public function setValue($value) {
     $this->value = isset($value) ? (string) $value : $value;
   }
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    // TODO: Implement validate() method.
-  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/TypedDataInterface.php b/core/lib/Drupal/Core/TypedData/TypedDataInterface.php
index 1a8ffe7..37ad97f 100644
--- a/core/lib/Drupal/Core/TypedData/TypedDataInterface.php
+++ b/core/lib/Drupal/Core/TypedData/TypedDataInterface.php
@@ -57,7 +57,21 @@ public function setValue($value);
   public function getString();
 
   /**
+   * Gets a list of validation constraints.
+   *
+   * @return array
+   *   Array of constraints, each being an instance of
+   *   \Symfony\Component\Validator\Constraint.
+   *
+   */
+  public function getConstraints();
+
+  /**
    * Validates the currently set data value.
+   *
+   * @return \Symfony\Component\Validator\ConstraintViolationListInterface
+   *   A list of constraint violations. If the list is empty, validation
+   *   succeeded.
    */
   public function validate();
 }
diff --git a/core/lib/Drupal/Core/TypedData/TypedDataManager.php b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
index a1522d8..39f3d1e 100644
--- a/core/lib/Drupal/Core/TypedData/TypedDataManager.php
+++ b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
@@ -10,12 +10,32 @@
 use Drupal\Component\Plugin\PluginManagerBase;
 use Drupal\Core\Plugin\Discovery\CacheDecorator;
 use Drupal\Core\Plugin\Discovery\HookDiscovery;
+use Drupal\Core\TypedData\Validation\MetadataFactory;
+use Drupal\Core\Validation\ConstraintManager;
+use Symfony\Component\Validator\ConstraintValidatorFactory;
+use Symfony\Component\Validator\Validator;
+use Symfony\Component\Validator\ValidatorInterface;
 
 /**
  * Manages data type plugins.
  */
 class TypedDataManager extends PluginManagerBase {
 
+  /**
+   * The validator used for validating typed data.
+   *
+   * @var \Symfony\Component\Validator\ValidatorInterface
+   */
+  protected $validator;
+
+  /**
+   * The validation constraint manager to use for instantiating constraints.
+   *
+   * @var \Drupal\Core\Validation\ConstraintManager
+   */
+  protected $constraintManager;
+
+
   public function __construct() {
     $this->discovery = new CacheDecorator(new HookDiscovery('data_type_info'), 'typed_data:types');
     $this->factory = new TypedDataFactory($this->discovery);
@@ -108,4 +128,53 @@ function create(array $definition, $value = NULL, array $context = array()) {
     }
     return $wrapper;
   }
+
+  /**
+   * Sets the validator for validating typed data.
+   *
+   * @param \Symfony\Component\Validator\ValidatorInterface $validator
+   *   The validator object to set.
+   */
+  public function setValidator(ValidatorInterface $validator) {
+    $this->validator = $validator;
+  }
+
+  /**
+   * Gets the validator for validating typed data.
+   *
+   * @return \Symfony\Component\Validator\ValidatorInterface
+   *   The validator object.
+   */
+  public function getValidator() {
+    if (!isset($this->validator)) {
+      $this->validator = new Validator(new MetadataFactory(), new ConstraintValidatorFactory());
+    }
+    return $this->validator;
+  }
+
+  /**
+   * Sets the validation constraint manager.
+   *
+   * The validation constraint manager is used to instantiate validation
+   * constraint plugins.
+   *
+   * @param \Drupal\Core\Validation\ConstraintManager
+   *   The constraint manager to set.
+   */
+  public function setValidationConstraintManager(ConstraintManager $constraintManager) {
+    $this->constraintManager = $constraintManager;
+  }
+
+  /**
+   * Gets the validation constraint manager.
+   *
+   * @return \Drupal\Core\Validation\ConstraintManager
+   *   The constraint manager.
+   */
+  public function getValidationConstraintManager() {
+    if (!isset($this->constraintManager)) {
+      $this->constraintManager = drupal_container()->get('validation.constraint');
+    }
+    return $this->constraintManager;
+  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/Validation/Metadata.php b/core/lib/Drupal/Core/TypedData/Validation/Metadata.php
new file mode 100644
index 0000000..e520253
--- /dev/null
+++ b/core/lib/Drupal/Core/TypedData/Validation/Metadata.php
@@ -0,0 +1,93 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\Core\TypedData\Validation\Metadata.
+ */
+
+namespace Drupal\Core\TypedData\Validation;
+
+use Drupal\Core\TypedData\TypedDataInterface;
+use Symfony\Component\Validator\ValidationVisitorInterface;
+use Symfony\Component\Validator\PropertyMetadataInterface;
+
+/**
+ * Typed data implementation of the validator MetadataInterface.
+ */
+class Metadata implements PropertyMetadataInterface {
+
+  /**
+   * The name of the property, or empty if this is the root.
+   *
+   * @var string
+   */
+  protected $name;
+
+  /**
+   * The typed data object the metadata is about.
+   *
+   * @var \Drupal\Core\TypedData\TypedDataInterface
+   */
+  protected $typedData;
+
+  /**
+   * The metadata factory used.
+   *
+   * @var \Drupal\Core\TypedData\Validation\MetadataFactory
+   */
+  protected $factory;
+
+  /**
+   * Constructs the object.
+   *
+   * @param \Drupal\Core\TypedData\TypedDataInterface $typed_data
+   *   The typed data object the metadata is about.
+   * @param $name
+   *   The name of the property to get metadata for. Leave empty, if
+   *   the data is the root of the typed data tree.
+   * @param \Drupal\Core\TypedData\Validation\MetadataFactory $factory
+   *   The factory to use for instantiating property metadata.
+   */
+  public function __construct(TypedDataInterface $typed_data, $name = '', MetadataFactory $factory) {
+    $this->typedData = $typed_data;
+    $this->name = $name;
+    $this->factory = $factory;
+  }
+
+  /**
+   * Implements MetadataInterface::accept().
+   */
+  public function accept(ValidationVisitorInterface $visitor, $typed_data, $group, $propertyPath) {
+
+    // @todo: Do we have to care about groups? Symfony class metadata has
+    // $propagatedGroup.
+
+    $visitor->visit($this, $typed_data->getValue(), $group, $propertyPath);
+  }
+
+  /**
+   * Implements MetadataInterface::findConstraints().
+   */
+  public function findConstraints($group) {
+    return $this->typedData->getConstraints();
+  }
+
+  /**
+   * Returns the name of the property.
+   *
+   * @return string The property name.
+   */
+  public function getPropertyName() {
+    return $this->name;
+  }
+
+  /**
+   * Extracts the value of the property from the given container.
+   *
+   * @param mixed $container The container to extract the property value from.
+   *
+   * @return mixed The value of the property.
+   */
+  public function getPropertyValue($container) {
+    return $this->typedData->getValue();
+  }
+}
\ No newline at end of file
diff --git a/core/lib/Drupal/Core/TypedData/Validation/MetadataFactory.php b/core/lib/Drupal/Core/TypedData/Validation/MetadataFactory.php
new file mode 100644
index 0000000..989119d
--- /dev/null
+++ b/core/lib/Drupal/Core/TypedData/Validation/MetadataFactory.php
@@ -0,0 +1,43 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\Core\TypedData\Validation\MetadataFactory.
+ */
+
+namespace Drupal\Core\TypedData\Validation;
+
+use Drupal\Core\TypedData\ComplexDataInterface;
+use Drupal\Core\TypedData\ListInterface;
+use Drupal\Core\TypedData\TypedDataInterface;
+use Symfony\Component\Validator\MetadataFactoryInterface;
+
+/**
+ * Typed data implementation of the validator MetadataFactoryInterface.
+ */
+class MetadataFactory implements MetadataFactoryInterface {
+
+  /**
+   * Implements MetadataFactoryInterface::getMetadataFor().
+   *
+   * @param \Drupal\Core\TypedData\TypedDataInterface $typed_data
+   *   Some typed data object containing the value to validate.
+   * @param $name
+   *   (optional) The name of the property to get metadata for. Leave empty, if
+   *   the data is the root of the typed data tree.
+   */
+  public function getMetadataFor($typed_data, $name = '') {
+    if (!$typed_data instanceof TypedDataInterface) {
+      throw new \InvalidArgumentException('The passed value must be a typed data object.');
+    }
+    $is_container = $typed_data instanceof ComplexDataInterface || $typed_data instanceof ListInterface;
+    $class = '\Drupal\Core\TypedData\Validation\\' . ($is_container ? 'PropertyContainerMetadata' : 'Metadata');
+    return new $class($typed_data, $name, $this);
+  }
+
+  /**
+   * Implements MetadataFactoryInterface::hasMetadataFor().
+   */
+  public function hasMetadataFor($value) {
+    return $value instanceof TypedDataInterface;
+  }
+}
diff --git a/core/lib/Drupal/Core/TypedData/Validation/PropertyContainerMetadata.php b/core/lib/Drupal/Core/TypedData/Validation/PropertyContainerMetadata.php
new file mode 100644
index 0000000..f33a729
--- /dev/null
+++ b/core/lib/Drupal/Core/TypedData/Validation/PropertyContainerMetadata.php
@@ -0,0 +1,47 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\Core\TypedData\Validation\PropertyContainerMetadata.
+ */
+
+namespace Drupal\Core\TypedData\Validation;
+
+use Drupal\Core\TypedData\ComplexDataInterface;
+use Drupal\Core\TypedData\ListInterface;
+use Symfony\Component\Validator\PropertyMetadataContainerInterface;
+use Symfony\Component\Validator\ValidationVisitorInterface;
+
+/**
+ * Typed data implementation of the validator MetadataInterface.
+ */
+class PropertyContainerMetadata extends Metadata implements PropertyMetadataContainerInterface {
+
+  /**
+   * Overrides Metadata::accept().
+   */
+  public function accept(ValidationVisitorInterface $visitor, $typed_data, $group, $propertyPath) {
+
+    $visitor->visit($this, $typed_data, $group, $propertyPath);
+    $pathPrefix = empty($propertyPath) ? '' : $propertyPath . '.';
+
+    foreach ($this->typedData as $name => $data) {
+      $metadata = $this->factory->getMetadataFor($typed_data, $name);
+      $metadata->accept($visitor, $data, $group, $pathPrefix . $name);
+    }
+  }
+
+  /**
+   * Implements PropertyMetadataContainerInterface::getPropertyMetadata().
+   */
+  public function getPropertyMetadata($property_name) {
+    if ($this->typedData instanceof ListInterface) {
+      return array(new PropertyMetadata($this->typedData[$property_name], $property_name));
+    }
+    elseif ($this->typedData instanceof ComplexDataInterface) {
+      return array(new PropertyMetadata($this->typedData->get($property_name), $property_name));
+    }
+    else {
+      throw new \LogicException("There are no known properties.");
+    }
+  }
+}
\ No newline at end of file
diff --git a/core/lib/Drupal/Core/Validation/ConstraintManager.php b/core/lib/Drupal/Core/Validation/ConstraintManager.php
new file mode 100644
index 0000000..c9da430
--- /dev/null
+++ b/core/lib/Drupal/Core/Validation/ConstraintManager.php
@@ -0,0 +1,55 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\Core\Validation\ConstraintManager.
+ */
+
+namespace Drupal\Core\Validation;
+
+use Drupal\Component\Plugin\Factory\DefaultFactory;
+use Drupal\Component\Plugin\PluginManagerBase;
+use Drupal\Component\Plugin\Discovery\DerivativeDiscoveryDecorator;
+use Drupal\Core\Plugin\Discovery\AlterDecorator;
+use Drupal\Core\Plugin\Discovery\AnnotatedClassDiscovery;
+
+/**
+ * Constraint plugin manager.
+ *
+ * Manages validation constraints based upon
+ * \Symfony\Component\Validator\Constraint, whereas Symfony constraints are
+ * added in via the SymfonyDiscoveryDecorator class. Constraint options are
+ * passed on as plugin configuration during plugin instantiation.
+ */
+class ConstraintManager extends PluginManagerBase {
+
+  /**
+   * Overrides \Drupal\Component\Plugin\PluginManagerBase::__construct().
+   */
+  public function __construct() {
+    $discovery = new SymfonyDiscoveryDecorator(new AnnotatedClassDiscovery('Validation', 'Constraint'));
+    $this->discovery = new AlterDecorator(new DerivativeDiscoveryDecorator($discovery), 'validation_constraint');
+    $this->factory = new DefaultFactory($this->discovery);
+  }
+
+  /**
+   * Returns a list of Constraints that apply to a certain type.
+   *
+   * @param string $type
+   *   The type to filter on.
+   * @param boolean $include_general
+   *   Whether or not to include the ones with an empty type.
+   */
+  public function getList($type = NULL, $include_general = TRUE) {
+    $constraints = array();
+    $definitions = $this->getDefinitions();
+    foreach ($definitions as $plugin_id => $definition) {
+      if ($type === NULL || $definition['type'] == $type) {
+        $constraints[$plugin_id] = $definition;
+      }
+      elseif ($type === '' && $include_general) {
+        $constraints[$plugin_id] = $definition;
+      }
+    }
+    return $constraints;
+  }
+}
diff --git a/core/lib/Drupal/Core/Validation/SymfonyDiscoveryDecorator.php b/core/lib/Drupal/Core/Validation/SymfonyDiscoveryDecorator.php
new file mode 100644
index 0000000..fc2224f
--- /dev/null
+++ b/core/lib/Drupal/Core/Validation/SymfonyDiscoveryDecorator.php
@@ -0,0 +1,95 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Plugin\Discovery\SymfonyDiscoveryDecorator.
+*/
+
+namespace Drupal\Core\Validation;
+
+use Drupal\Component\Plugin\Discovery\DiscoveryInterface;
+
+/**
+ * Adds definitions for constraints shipped with Symfony.
+ */
+class SymfonyDiscoveryDecorator implements DiscoveryInterface {
+
+  /**
+   * The Discovery object being decorated.
+   *
+   * @var \Drupal\Component\Plugin\Discovery\DiscoveryInterface
+   */
+  protected $decorated;
+
+  /**
+   * Constructs the decorator object.
+   *
+   * It uses the DiscoveryInterface object it should decorate.
+   *
+   * @param \Drupal\Component\Plugin\Discovery\DiscoveryInterface $decorated
+   *   The object implementing DiscoveryInterface that is being decorated.
+   */
+  public function __construct(DiscoveryInterface $decorated) {
+    $this->decorated = $decorated;
+  }
+
+  /**
+   * Implements \Drupal\Component\Plugin\Discovery\DiscoveryInterface::getDefinition().
+   */
+  public function getDefinition($plugin_id) {
+    $definitions = $this->getDefinitions();
+    if (isset($definitions[$plugin_id])) {
+      return $definitions[$plugin_id];
+    }
+  }
+
+  /**
+   * Implements \Drupal\Component\Plugin\Discovery\DiscoveryInterface::getDefinitions().
+   */
+  public function getDefinitions() {
+    $definitions = $this->decorated->getDefinitions();
+    // @todo: Care about types.
+
+    $definitions['Min'] = array(
+      'label' => t('Minimum value'),
+      'class' => '\Symfony\Component\Validator\Constraints\Min'
+    );
+    $definitions['MinLength'] = array(
+      'label' => t('Minimum length'),
+      'class' => '\Symfony\Component\Validator\Constraints\MinLength'
+    );
+    $definitions['Max'] = array(
+      'label' => t('Maximum value'),
+      'class' => '\Symfony\Component\Validator\Constraints\Max'
+    );
+    $definitions['MaxLength'] = array(
+      'label' => t('Maximum length'),
+      'class' => '\Symfony\Component\Validator\Constraints\MaxLength'
+    );
+    $definitions['Null'] = array(
+      'label' => t('Null'),
+      'class' => '\Symfony\Component\Validator\Constraints\Null'
+    );
+    $definitions['NotNull'] = array(
+      'label' => t('Not null'),
+      'class' => '\Symfony\Component\Validator\Constraints\NotNull'
+    );
+    $definitions['Blank'] = array(
+      'label' => t('Blank'),
+      'class' => '\Symfony\Component\Validator\Constraints\Blank'
+    );
+    $definitions['NotBlank'] = array(
+      'label' => t('Not blank'),
+      'class' => '\Symfony\Component\Validator\Constraints\NotBlank'
+    );
+
+    return $definitions;
+  }
+
+  /**
+   * Passes through all unknown calls onto the decorated object
+   */
+  public function __call($method, $args) {
+    return call_user_func_array(array($this->decorated, $method), $args);
+  }
+}
diff --git a/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php b/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
index 00e4c95..c54f3f1 100644
--- a/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
@@ -16,6 +16,13 @@
  */
 class TypedDataTest extends WebTestBase {
 
+  /**
+   * The typed data manager to use.
+   *
+   * @var \Drupal\Core\TypedData\TypedDataManager
+   */
+  protected $typedData;
+
   public static function getInfo() {
     return array(
       'name' => 'Test typed data objects',
@@ -24,6 +31,11 @@ public static function getInfo() {
     );
   }
 
+  public function setUp() {
+    parent::setup();
+    $this->typedData = typed_data();
+  }
+
   /**
    * Tests the basics around constructing and working with data wrappers.
    */
@@ -127,4 +139,65 @@ public function testGetAndSet() {
     $wrapper->setValue(NULL);
     $this->assertNull($wrapper->getValue(), 'Binary wrapper is null-able.');
   }
+
+  /**
+   * Tests typed data validation.
+   */
+  public function testTypedDataValidation() {
+    $definition = array(
+      'type' => 'integer',
+      'constraints' => array(
+        'Min' => array('limit' => 5),
+      ),
+    );
+    $violations = $this->typedData->create($definition, 10)->validate();
+    $this->assertEqual($violations->count(), 0);
+
+    $integer = $this->typedData->create($definition, 1);
+    $violations = $integer->validate();
+    $this->assertEqual($violations->count(), 1);
+    // @todo: Translation.
+    $this->assertEqual($violations[0]->getMessage(), 'This value should be 5 or more.');
+    $this->assertEqual($violations[0]->getPropertyPath(), '');
+    $this->assertEqual($violations[0]->getPropertyPath(), '');
+    $this->assertIdentical($violations[0]->getRoot(), $integer, 'Root object returned.');
+
+    // Test having multiple violations.
+    $definition = array(
+      'type' => 'integer',
+      'constraints' => array(
+        'Min' => array('limit' => 5),
+        'Null' => array(),
+      ),
+    );
+    $violations = $this->typedData->create($definition, 10)->validate();
+    $this->assertEqual($violations->count(), 1);
+    $violations = $this->typedData->create($definition, 1)->validate();
+    $this->assertEqual($violations->count(), 2);
+
+    // Test validating property containers.
+    $definition = array(
+      'type' => 'integer_field',
+      'constraints' => array(
+        'NotNull' => array(),
+      ),
+    );
+    // Tests the Min constraint on the integer item.
+    // @see IntegerItem::getPropertyDefinitions()
+    // @todo: Replace it with a proper test.
+    $field_item = $this->typedData->create($definition, array('value' => 10));
+    $violations = $field_item->validate();
+    $this->assertEqual($violations->count(), 0);
+
+    $field_item = $this->typedData->create($definition, array('value' => 1));
+    $violations = $field_item->validate();
+    $this->assertEqual($violations->count(), 1);
+
+    // Test that the field item may not be empty.
+    $field_item = $this->typedData->create($definition);
+    $violations = $field_item->validate();
+    // @todo: This does not work as an empty typed data object is passed to
+    // the constraint. Fix that.
+    $this->assertEqual($violations->count(), 1);
+  }
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Validation/ValidationConstraintTest.php b/core/modules/system/lib/Drupal/system/Tests/Validation/ValidationConstraintTest.php
new file mode 100644
index 0000000..6b38926
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/Validation/ValidationConstraintTest.php
@@ -0,0 +1,35 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Validation\ValidationConstraintTest.
+*/
+
+namespace Drupal\system\Tests\Validation;
+
+use Drupal\simpletest\UnitTestBase;
+use Drupal\Core\Plugin\Validation\Constraint;
+
+/**
+ * Tests the Drupal\Core\Validation\Constraint class.
+ */
+class ValidationConstraintTest extends UnitTestBase {
+
+  public static function getInfo() {
+    return array(
+      'name' => 'ValidationConstraintTest',
+      'description' => "Test constraint.",
+      'group' => 'Validation',
+    );
+  }
+
+  /**
+   * Tests NotNullConstraint.
+   */
+  public function testNotNullConstraint() {
+    $constraint = new Constraint\NotNullConstraint(array(), array());
+    $this->assertTrue($constraint->validate(1));
+    $this->assertTrue($constraint->validate(0));
+    $this->assertFalse($constraint->validate(NULL));
+  }
+}