diff --git a/core/lib/Drupal/Core/Entity/ContentEntityBase.php b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
index 7c68f0a..709ba90 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
@@ -601,7 +601,7 @@ public function onChange($name) {
   /**
    * {@inheritdoc}
    *
-   * @return \Drupal\Core\Entity\EntityInterface
+   * @return \Drupal\Core\Entity\ContentEntityInterface
    */
   public function getTranslation($langcode) {
     // Ensure we always use the default language code when dealing with the
diff --git a/core/lib/Drupal/Core/Entity/Entity.php b/core/lib/Drupal/Core/Entity/Entity.php
index 178fe51..2dffe2a 100644
--- a/core/lib/Drupal/Core/Entity/Entity.php
+++ b/core/lib/Drupal/Core/Entity/Entity.php
@@ -45,6 +45,14 @@
   protected $routeProvider;
 
   /**
+   * {@inheritdoc}
+   */
+  public static function createDataDefinition($data_type) {
+    // @todo: Implement a proper data definition class for entities.
+    return DataDefinition::create($data_type);
+  }
+
+  /**
    * Constructs an Entity object.
    *
    * @param array $values
diff --git a/core/lib/Drupal/Core/Field/FieldDefinition.php b/core/lib/Drupal/Core/Field/FieldDefinition.php
index 882d086..51b6338 100644
--- a/core/lib/Drupal/Core/Field/FieldDefinition.php
+++ b/core/lib/Drupal/Core/Field/FieldDefinition.php
@@ -8,7 +8,6 @@
 namespace Drupal\Core\Field;
 
 use Drupal\Core\Entity\EntityInterface;
-use Drupal\Core\TypedData\DataDefinition;
 use Drupal\Core\TypedData\ListDefinition;
 
 /**
@@ -17,6 +16,22 @@
 class FieldDefinition extends ListDefinition implements FieldDefinitionInterface {
 
   /**
+   * The field type.
+   *
+   * @var string
+   */
+  protected $type;
+
+  /**
+   * An array of field property definitions.
+   *
+   * @var \Drupal\Core\TypedData\DataDefinitionInterface[]
+   *
+   * @see \Drupal\Core\TypedData\ComplexDataDefinitionInterface::getPropertyDefinitions()
+   */
+  protected $propertyDefinitions;
+
+  /**
    * Creates a new field definition.
    *
    * @param string $type
@@ -26,7 +41,10 @@ class FieldDefinition extends ListDefinition implements FieldDefinitionInterface
    *   A new field definition object.
    */
   public static function create($type) {
-    return new static(array(), DataDefinition::create('field_item:' . $type));
+    $field_definition = new static(array());
+    $field_definition->type = $type;
+    $field_definition->itemDefinition = FieldItemDefinition::create($field_definition);
+    return $field_definition;
   }
 
   /**
@@ -54,10 +72,7 @@ public function setName($name) {
    * {@inheritdoc}
    */
   public function getType() {
-    $data_type = $this->getItemDefinition()->getDataType();
-    // Cut of the leading field_item: prefix from 'field_item:FIELD_TYPE'.
-    $parts = explode(':', $data_type);
-    return $parts[1];
+    return $this->type;
   }
 
   /**
@@ -107,13 +122,6 @@ public function setSetting($setting_name, $value) {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyNames() {
-    return array_keys(\Drupal::typedDataManager()->create($this->getItemDefinition())->getPropertyDefinitions());
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function isTranslatable() {
     return !empty($this->definition['translatable']);
   }
@@ -201,4 +209,69 @@ public function getDefaultValue(EntityInterface $entity) {
     return $this->getSetting('default_value');
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinition($name) {
+    if (!isset($this->propertyDefinitions)) {
+      $this->getPropertyDefinitions();
+    }
+    if (isset($this->propertyDefinitions[$name])) {
+      return $this->propertyDefinitions[$name];
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinitions() {
+    if (!isset($this->propertyDefinitions)) {
+      $class = $this->getFieldItemClass();
+      $this->propertyDefinitions = $class::propertyDefinitions($this);
+    }
+    return $this->propertyDefinitions;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyNames() {
+    return array_keys($this->getPropertyDefinitions());
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMainPropertyName() {
+    $class = $this->getFieldItemClass();
+    return $class::getMainPropertyName();
+  }
+
+  /**
+   * Helper to retrieve the field item class.
+   *
+   * @todo: Remove once getClass() adds in defaults. See
+   * https://drupal.org/node/2116341.
+   */
+  protected function getFieldItemClass() {
+    if ($class = $this->itemDefinition->getClass()) {
+      return $class;
+    }
+    else {
+      $type_definition = \Drupal::typedDataManager()
+        ->getDefinition($this->itemDefinition->getDataType());
+      return $type_definition['class'];
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __sleep() {
+    // Do not serialize the statically cached property definitions.
+    $vars = get_object_vars($this);
+    unset($vars['propertyDefinitions']);
+    return array_keys($vars);
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Field/FieldDefinitionInterface.php b/core/lib/Drupal/Core/Field/FieldDefinitionInterface.php
index 76f0ef9..4e95165 100644
--- a/core/lib/Drupal/Core/Field/FieldDefinitionInterface.php
+++ b/core/lib/Drupal/Core/Field/FieldDefinitionInterface.php
@@ -209,4 +209,36 @@ public function isMultiple();
    */
   public function getDefaultValue(EntityInterface $entity);
 
+  /**
+   * Gets the definition of a contained property.
+   *
+   * @param string $name
+   *   The name of property.
+   *
+   * @return \Drupal\Core\TypedData\DataDefinitionInterface|null
+   *   The definition of the property or NULL if the property does not exist.
+   */
+  public function getPropertyDefinition($name);
+
+  /**
+   * Gets an array of property definitions of contained properties.
+   *
+   * @return \Drupal\Core\TypedData\DataDefinitionInterface[]
+   *   An array of property definitions of contained properties, keyed by
+   *   property name.
+   */
+  public function getPropertyDefinitions();
+
+  /**
+   * Returns the name of the main property, if any.
+   *
+   * Some field items consist mainly of one main property, e.g. the value of a
+   * text field or the @code target_id @endcode of an entity reference. If the
+   * field item has no main property, the method returns NULL.
+   *
+   * @return string|null
+   *   The name of the value property, or NULL if there is none.
+   */
+  public function getMainPropertyName();
+
 }
diff --git a/core/lib/Drupal/Core/Field/FieldItemBase.php b/core/lib/Drupal/Core/Field/FieldItemBase.php
index b5b0f3f..cec6d6e 100644
--- a/core/lib/Drupal/Core/Field/FieldItemBase.php
+++ b/core/lib/Drupal/Core/Field/FieldItemBase.php
@@ -26,6 +26,23 @@
   /**
    * {@inheritdoc}
    */
+  public static function createDataDefinition($data_type) {
+    // The data type of a field item is in the form of "field_item:$field_type".
+    $parts = explode(':', $data_type, 2);
+    $field_definition = FieldDefinition::create($parts[1]);
+    return $field_definition->getItemDefinition();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getMainPropertyName() {
+    return 'value';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function __construct(DataDefinitionInterface $definition, $name = NULL, TypedDataInterface $parent = NULL) {
     parent::__construct($definition, $name, $parent);
     // Initialize computed properties by default, such that they get cloned
@@ -211,11 +228,4 @@ public function delete() { }
    */
   public function deleteRevision() { }
 
-  /**
-   * {@inheritdoc}
-   */
-  public function getMainPropertyName() {
-    return 'value';
-  }
-
 }
diff --git a/core/lib/Drupal/Core/Field/FieldItemDefinition.php b/core/lib/Drupal/Core/Field/FieldItemDefinition.php
new file mode 100644
index 0000000..28a2337
--- /dev/null
+++ b/core/lib/Drupal/Core/Field/FieldItemDefinition.php
@@ -0,0 +1,62 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Field\FieldItemDefinition.
+ */
+
+namespace Drupal\Core\Field;
+
+use Drupal\Core\TypedData\ComplexDataDefinitionInterface;
+use Drupal\Core\TypedData\DataDefinition;
+
+/**
+ * A class for defining field items.
+ */
+class FieldItemDefinition extends DataDefinition implements ComplexDataDefinitionInterface {
+
+  /**
+   * The field definition the item definition belongs to.
+   *
+   * @var \Drupal\Core\Field\FieldDefinitionInterface
+   */
+  protected $fieldDefinition;
+
+  /**
+   * Creates a new field item definition.
+   *
+   * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
+   *   The field definition the item definition belongs to.
+   *
+   * @return static
+   *   A new FieldItemDefinition object.
+   */
+  public static function create($field_definition) {
+    $definition['type'] = 'field_item:' . $field_definition->getType();
+    $item_definition = new static($definition);
+    $item_definition->fieldDefinition = $field_definition;
+    return $item_definition;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinition($name) {
+    return $this->fieldDefinition->getPropertyDefinition($name);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinitions() {
+    return $this->fieldDefinition->getPropertyDefinitions();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMainPropertyName() {
+    return $this->fieldDefinition->getMainPropertyName();
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Field/FieldItemInterface.php b/core/lib/Drupal/Core/Field/FieldItemInterface.php
index 2cdd0c3..ee5c06a 100644
--- a/core/lib/Drupal/Core/Field/FieldItemInterface.php
+++ b/core/lib/Drupal/Core/Field/FieldItemInterface.php
@@ -24,6 +24,31 @@
 interface FieldItemInterface extends ComplexDataInterface {
 
   /**
+   * Defines field item properties.
+   *
+   * @return \Drupal\Core\TypedData\DataDefinitionInterface[]
+   *   An array of property definitions of contained properties, keyed by
+   *   property name.
+   *
+   * @see \Drupal\Core\Field\FieldDefinition
+   */
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition);
+
+  /**
+   * Returns the name of the main property, if any.
+   *
+   * Some field items consist mainly of one main property, e.g. the value of a
+   * text field or the @code target_id @endcode of an entity reference. If the
+   * field item has no main property, the method returns NULL.
+   *
+   * @return string|null
+   *   The name of the value property, or NULL if there is none.
+   *
+   * @see \Drupal\Core\Field\FieldDefinition
+   */
+  public static function getMainPropertyName();
+
+  /**
    * Gets the entity that field belongs to.
    *
    * @return \Drupal\Core\Entity\EntityInterface
@@ -136,20 +161,4 @@ public function delete();
    */
   public function deleteRevision();
 
-  /**
-   * Returns the name of the main property, if any.
-   *
-   * Some field items consist mainly of one main property, e.g. the value of a
-   * text field or the @code target_id @endcode of an entity reference. If the
-   * field item has no main property, the method returns NULL.
-   *
-   * @return string|null
-   *   The name of the value property, or NULL if there is none.
-   *
-   * @todo: Move this to ComplexDataInterface once we improved Typed data to do
-   *   not enforce having all methods on the data objects.
-   *   https://drupal.org/node/2002134
-   */
-  public function getMainPropertyName();
-
 }
diff --git a/core/lib/Drupal/Core/Field/FieldItemList.php b/core/lib/Drupal/Core/Field/FieldItemList.php
index 1af3254..17c1664 100644
--- a/core/lib/Drupal/Core/Field/FieldItemList.php
+++ b/core/lib/Drupal/Core/Field/FieldItemList.php
@@ -41,6 +41,15 @@ class FieldItemList extends ItemList implements FieldItemListInterface {
   /**
    * {@inheritdoc}
    */
+  public static function createDataDefinition($data_type) {
+    // The data type of a field item is in the form of "field_item:$field_type".
+    $parts = explode(':', $data_type, 2);
+    return FieldDefinition::create($parts[1]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function __construct(DataDefinitionInterface $definition, $name = NULL, TypedDataInterface $parent = NULL) {
     parent::__construct($definition, $name, $parent);
     // Always initialize one empty item as most times a value for at least one
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/BooleanItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/BooleanItem.php
index 994957c..5a83b98 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/BooleanItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/BooleanItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -23,23 +24,13 @@
 class BooleanItem extends FieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see BooleanItem::getPropertyDefinitions()
-   *
-   * @var array
+   * {@inheritdoc}
    */
-  static $propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('boolean')
+      ->setLabel(t('Boolean value'));
 
-  /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
-   */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('boolean')
-        ->setLabel(t('Boolean value'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 
 }
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/DateItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/DateItem.php
index 59984c8..0652582 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/DateItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/DateItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 
 /**
@@ -22,25 +23,14 @@
 class DateItem extends FieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see DateItem::getPropertyDefinitions()
-   *
-   * @var array
+   * {@inheritdoc}
    */
-  static $propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = array(
+      'type' => 'date',
+      'label' => t('Date value'),
+    );
 
-  /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
-   */
-  public function getPropertyDefinitions() {
-
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = array(
-        'type' => 'date',
-        'label' => t('Date value'),
-      );
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 }
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EmailItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EmailItem.php
index 5a2c107..09aea19 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EmailItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EmailItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -23,24 +24,13 @@
 class EmailItem extends FieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see EmailItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
-   * Implements ComplexDataInterface::getPropertyDefinitions().
+   * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('email')
+      ->setLabel(t('E-mail value'));
 
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('email')
-        ->setLabel(t('E-mail value'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 
 
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
index 40f7a3a..f3b1cd6 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -30,56 +31,49 @@
 class EntityReferenceItem extends FieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see EntityReferenceItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
+   * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    $settings = $this->definition->getSettings();
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $settings = $field_definition->getSettings();
     $target_type = $settings['target_type'];
 
-    // Definitions vary by entity type and bundle, so key them accordingly.
-    $key = $target_type . ':';
-    $key .= isset($settings['target_bundle']) ? $settings['target_bundle'] : '';
-
-    if (!isset(static::$propertyDefinitions[$key])) {
-      $target_type_info = \Drupal::entityManager()->getDefinition($target_type);
-      if ($target_type_info->isSubclassOf('\Drupal\Core\Entity\ContentEntityInterface')) {
-        // @todo: Lookup the entity type's ID data type and use it here.
-        // https://drupal.org/node/2107249
-        static::$propertyDefinitions[$key]['target_id'] = DataDefinition::create('integer')
-          ->setLabel(t('Entity ID'))
-          ->setConstraints(array(
-            'Range' => array('min' => 0),
-          ));
-      }
-      else {
-        static::$propertyDefinitions[$key]['target_id'] = DataDefinition::create('string')
-          ->setLabel(t('Entity ID'));
-      }
-
-      static::$propertyDefinitions[$key]['entity'] = DataDefinition::create('entity_reference')
-        ->setLabel(t('Entity'))
-        ->setDescription(t('The referenced entity'))
-        // The entity object is computed out of the entity ID.
-        ->setComputed(TRUE)
-        ->setReadOnly(FALSE)
+    $target_type_info = \Drupal::entityManager()->getDefinition($target_type);
+    if ($target_type_info->isSubclassOf('\Drupal\Core\Entity\ContentEntityInterface')) {
+      // @todo: Lookup the entity type's ID data type and use it here.
+      // https://drupal.org/node/2107249
+      $properties['target_id'] = DataDefinition::create('integer')
+        ->setLabel(t('Entity ID'))
         ->setConstraints(array(
-          'EntityType' => $settings['target_type'],
+          'Range' => array('min' => 0),
         ));
+    }
+    else {
+      $properties['target_id'] = DataDefinition::create('string')
+        ->setLabel(t('Entity ID'));
+    }
 
-      if (isset($settings['target_bundle'])) {
-        static::$propertyDefinitions[$key]['entity']->addConstraint('Bundle', $settings['target_bundle']);
-      }
+    $properties['entity'] = DataDefinition::create('entity_reference')
+      ->setLabel(t('Entity'))
+      ->setDescription(t('The referenced entity'))
+      // The entity object is computed out of the entity ID.
+      ->setComputed(TRUE)
+      ->setReadOnly(FALSE)
+      ->setConstraints(array(
+        'EntityType' => $settings['target_type'],
+      ));
+
+    if (isset($settings['target_bundle'])) {
+      $properties['entity']->addConstraint('Bundle', $settings['target_bundle']);
     }
-    return static::$propertyDefinitions[$key];
+
+    return $properties;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getMainPropertyName() {
+    return 'target_id';
   }
 
   /**
@@ -142,11 +136,4 @@ public function onChange($property_name) {
     parent::onChange($property_name);
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  public function getMainPropertyName() {
-    return 'target_id';
-  }
-
 }
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php
index e489a2f..421acc5 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -23,23 +24,12 @@
 class FloatItem extends FieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see IntegerItem::getPropertyDefinitions()
-   *
-   * @var array
+   * {@inheritdoc}
    */
-  static $propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('float')
+      ->setLabel(t('Float value'));
 
-  /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
-   */
-  public function getPropertyDefinitions() {
-
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('float')
-        ->setLabel(t('Float value'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 }
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/IntegerItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/IntegerItem.php
index 82f088a..68b5d45 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/IntegerItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/IntegerItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -23,23 +24,12 @@
 class IntegerItem extends FieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see IntegerItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('integer')
+      ->setLabel(t('Integer value'));
 
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('integer')
-        ->setLabel(t('Integer value'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 }
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php
index bd4d877..fee72c2 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/LanguageItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\Language\Language;
 use Drupal\Core\TypedData\DataDefinition;
@@ -29,30 +30,20 @@
 class LanguageItem extends FieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see LanguageItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
+   * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('string')
-        ->setLabel(t('Language code'));
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('string')
+      ->setLabel(t('Language code'));
 
-      static::$propertyDefinitions['language'] = DataDefinition::create('language_reference')
-        ->setLabel(t('Language object'))
-        ->setDescription(t('The referenced language'))
+    $properties['language'] = DataDefinition::create('language_reference')
+      ->setLabel(t('Language object'))
+      ->setDescription(t('The referenced language'))
       // The language object is retrieved via the language code.
-        ->setComputed(TRUE)
-        ->setReadOnly(FALSE);
-    }
-    return static::$propertyDefinitions;
+      ->setComputed(TRUE)
+      ->setReadOnly(FALSE);
+
+    return $properties;
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/MapItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/MapItem.php
index 957b0e8..23f62bd 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/MapItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/MapItem.php
@@ -8,6 +8,8 @@
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
 use Drupal\Core\Field\FieldItemBase;
+use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Core\TypedData\DataDefinition;
 
 /**
  * Defines the 'map' entity field type.
@@ -15,7 +17,7 @@
  * @FieldType(
  *   id = "map",
  *   label = @Translation("Map"),
- *   description = @Translation("An entity field containing a map value."),
+ *   description = @Translation("An entity field for storing a serialized array of values."),
  *   configurable = FALSE
  * )
  */
@@ -24,6 +26,34 @@ class MapItem extends FieldItemBase {
   /**
    * {@inheritdoc}
    */
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    // There aren't any properties we can define statically.
+    return array();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinitions() {
+    // Come up with some run-time property definitions, such that property
+    // objects can be used for all map values.
+    $definitions = parent::getPropertyDefinitions();
+    foreach ($this->values as $name => $value) {
+      $definitions[$name] = DataDefinition::create('any');
+    }
+    return $definitions;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinition($name) {
+    return array_key_exists($name, $this->values) ? DataDefinition::create('any') : FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function setValue($values, $notify = TRUE) {
     $this->values = array();
     if (!isset($values)) {
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
index 9c63b33..7c653f7 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -23,23 +24,12 @@
 class StringItem extends FieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see StringItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('string')
+      ->setLabel(t('Text value'));
 
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('string')
-        ->setLabel(t('Text value'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 }
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
index c1be221..ebb8e2f 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -23,23 +24,13 @@
 class UriItem extends FieldItemBase {
 
   /**
-   * Field definitions of the contained properties.
-   *
-   * @see self::getPropertyDefinitions()
-   *
-   * @var array
+   * {@inheritdoc}
    */
-  static $propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('uri')
+      ->setLabel(t('URI value'));
 
-  /**
-   * Implements ComplexDataInterface::getPropertyDefinitions().
-   */
-  public function getPropertyDefinitions() {
-    if (!isset(self::$propertyDefinitions)) {
-      self::$propertyDefinitions['value'] = DataDefinition::create('uri')
-        ->setLabel(t('URI value'));
-    }
-    return self::$propertyDefinitions;
+    return $properties;
   }
 
 }
diff --git a/core/lib/Drupal/Core/TypedData/ComplexDataDefinitionBase.php b/core/lib/Drupal/Core/TypedData/ComplexDataDefinitionBase.php
new file mode 100644
index 0000000..9be93e2
--- /dev/null
+++ b/core/lib/Drupal/Core/TypedData/ComplexDataDefinitionBase.php
@@ -0,0 +1,48 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\TypedData\ComplexDataDefinitionBase.
+ */
+
+namespace Drupal\Core\TypedData;
+
+/**
+ * Base class for complex data definitions.
+ */
+abstract class ComplexDataDefinitionBase extends DataDefinition implements ComplexDataDefinitionInterface {
+
+  /**
+   * An array of data definitions.
+   *
+   * @var \Drupal\Core\TypedData\DataDefinitionInterface[]
+   *
+   * @see ComplexDataDefinitionBase::getPropertyDefinitions()
+   */
+  protected $propertyDefinitions;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinition($name) {
+    if (!isset($this->propertyDefinitions)) {
+      $this->getPropertyDefinitions();
+    }
+    if (isset($this->propertyDefinitions[$name])) {
+      return $this->propertyDefinitions[$name];
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMainPropertyName() {
+    return NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  abstract public function getPropertyDefinitions();
+
+}
diff --git a/core/lib/Drupal/Core/TypedData/ComplexDataDefinitionInterface.php b/core/lib/Drupal/Core/TypedData/ComplexDataDefinitionInterface.php
new file mode 100644
index 0000000..dbdad24
--- /dev/null
+++ b/core/lib/Drupal/Core/TypedData/ComplexDataDefinitionInterface.php
@@ -0,0 +1,47 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\TypedData\ComplexDataDefinitionInterface.
+ */
+
+namespace Drupal\Core\TypedData;
+
+/**
+ * Interface for complex data definitions.
+ */
+interface ComplexDataDefinitionInterface extends DataDefinitionInterface  {
+
+  /**
+   * Gets the definition of a contained property.
+   *
+   * @param string $name
+   *   The name of property.
+   *
+   * @return \Drupal\Core\TypedData\DataDefinitionInterface|null
+   *   The definition of the property or NULL if the property does not exist.
+   */
+  public function getPropertyDefinition($name);
+
+  /**
+   * Gets an array of property definitions of contained properties.
+   *
+   * @return \Drupal\Core\TypedData\DataDefinitionInterface[]
+   *   An array of property definitions of contained properties, keyed by
+   *   property name.
+   */
+  public function getPropertyDefinitions();
+
+  /**
+   * Returns the name of the main property, if any.
+   *
+   * Some field items consist mainly of one main property, e.g. the value of a
+   * text field or the @code target_id @endcode of an entity reference. If the
+   * field item has no main property, the method returns NULL.
+   *
+   * @return string|null
+   *   The name of the value property, or NULL if there is none.
+   */
+  public function getMainPropertyName();
+
+}
diff --git a/core/lib/Drupal/Core/TypedData/ComplexDataInterface.php b/core/lib/Drupal/Core/TypedData/ComplexDataInterface.php
index 438ea6e..13dfa19 100644
--- a/core/lib/Drupal/Core/TypedData/ComplexDataInterface.php
+++ b/core/lib/Drupal/Core/TypedData/ComplexDataInterface.php
@@ -99,6 +99,10 @@ public function setPropertyValues($values);
    *
    * @return array|FALSE
    *   The definition of the property or FALSE if the property does not exist.
+   *
+   * @deprecated
+   *   Use $this->getDefinition()->getPropertyDefinition() instead).
+   *   See \Drupal\Core\TypedData\ComplexDataDefinitionInterface.
    */
   public function getPropertyDefinition($name);
 
@@ -108,6 +112,10 @@ public function getPropertyDefinition($name);
    * @return \Drupal\Core\TypedData\DataDefinitionInterface[]
    *   An array of property definitions of contained properties, keyed by
    *   property name.
+   *
+   * @deprecated
+   *   Use $this->getDefinition()->getPropertyDefinitions() instead).
+   *   See \Drupal\Core\TypedData\ComplexDataDefinitionInterface.
    */
   public function getPropertyDefinitions();
 
diff --git a/core/lib/Drupal/Core/TypedData/DataDefinitionInterface.php b/core/lib/Drupal/Core/TypedData/DataDefinitionInterface.php
index e026fe8..d5eaf14 100644
--- a/core/lib/Drupal/Core/TypedData/DataDefinitionInterface.php
+++ b/core/lib/Drupal/Core/TypedData/DataDefinitionInterface.php
@@ -14,7 +14,13 @@
  * For example, a plugin could describe its parameters using data definitions
  * in order to specify what kind of data is required for it.
  *
+ * Definitions that describe lists or complex data have to implement the
+ * respective interfaces, such that the metadata about contained list items or
+ * properties can be retrieved from the definition.
+ *
  * @see \Drupal\Core\TypedData\DataDefinition
+ * @see \Drupal\Core\TypedData\ListDefinitionInterface
+ * @see \Drupal\Core\TypedData\ComplexDataDefinitionInterface
  */
 interface DataDefinitionInterface {
 
diff --git a/core/lib/Drupal/Core/TypedData/ListDefinition.php b/core/lib/Drupal/Core/TypedData/ListDefinition.php
index 4963107..820603c 100644
--- a/core/lib/Drupal/Core/TypedData/ListDefinition.php
+++ b/core/lib/Drupal/Core/TypedData/ListDefinition.php
@@ -34,12 +34,10 @@ public static function create($item_type) {
 
   /**
    * {@inheritdoc}
-   *
-   * @param
    */
   public function __construct(array $definition = array(), DataDefinitionInterface $item_definition = NULL) {
-    parent::__construct($definition);
-    $this->itemDefinition = isset($item_definition) ? $item_definition : DataDefinition::create('any');
+    $this->definition = $definition;
+    $this->itemDefinition = $item_definition;
   }
 
   /**
diff --git a/core/lib/Drupal/Core/TypedData/ListDefinitionInterface.php b/core/lib/Drupal/Core/TypedData/ListDefinitionInterface.php
index c07d60e..613c1f8 100644
--- a/core/lib/Drupal/Core/TypedData/ListDefinitionInterface.php
+++ b/core/lib/Drupal/Core/TypedData/ListDefinitionInterface.php
@@ -12,6 +12,8 @@
  *
  * This interface is present on a data definition if it describes a list. The
  * actual lists implement the \Drupal\Core\TypedData\ListInterface.
+ *
+ * @see \Drupal\Core\TypedData\ListDefinition
  */
 interface ListDefinitionInterface extends DataDefinitionInterface {
 
diff --git a/core/lib/Drupal/Core/TypedData/ListInterface.php b/core/lib/Drupal/Core/TypedData/ListInterface.php
index 53f5eac..d60eb64 100644
--- a/core/lib/Drupal/Core/TypedData/ListInterface.php
+++ b/core/lib/Drupal/Core/TypedData/ListInterface.php
@@ -19,6 +19,17 @@
 interface ListInterface extends TypedDataInterface, \ArrayAccess, \Countable, \Traversable {
 
   /**
+   * Creates a new list definition.
+   *
+   * @param string $data_type
+   *   The data type of the list items.
+   *
+   * @return \Drupal\Core\TypedData\ListDefinitionInterface
+   *   A list definition for the given data type.
+   */
+  public static function createDataDefinition($data_type);
+
+  /**
    * Determines whether the list contains any non-empty items.
    *
    * @return boolean
diff --git a/core/lib/Drupal/Core/TypedData/MapDefinition.php b/core/lib/Drupal/Core/TypedData/MapDefinition.php
new file mode 100644
index 0000000..d848211
--- /dev/null
+++ b/core/lib/Drupal/Core/TypedData/MapDefinition.php
@@ -0,0 +1,88 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\TypedData\MapDefinition.
+ */
+
+namespace Drupal\Core\TypedData;
+
+/**
+ * Data definition class for maps.
+ */
+class MapDefinition extends ComplexDataDefinitionBase {
+
+  /**
+   * The name of the main property, or NULL if there is none.
+   *
+   * @var string
+   */
+  protected $mainPropertyName = NULL;
+
+  /**
+   * Creates a new map definition.
+   *
+   * @param string $type
+   *   (optional) The data type of the map. Defaults to 'map'.
+   *
+   * @return static
+   *   A new MapDefinition object.
+   */
+  public static function create($type = 'map') {
+    $definition['type'] = $type;
+    return new static($definition);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinitions() {
+    if (!isset($this->propertyDefinitions)) {
+      $this->propertyDefinitions = array();
+    }
+    return $this->propertyDefinitions;
+  }
+
+  /**
+   * Sets the definition of a map property.
+   *
+   * @param string $name
+   *   The name of the property to define.
+   * @param \Drupal\Core\TypedData\DataDefinitionInterface|null $definition
+   *   (optional) The property definition to set, or NULL to unset it.
+   *
+   * @return static
+   *   The object itself for chaining.
+   */
+  public function setPropertyDefinition($name, DataDefinitionInterface $definition = NULL) {
+    if (isset($definition)) {
+      $this->propertyDefinitions[$name] = $definition;
+    }
+    else {
+      unset($this->propertyDefinitions[$name]);
+    }
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMainPropertyName() {
+    return $this->mainPropertyName;
+  }
+
+  /**
+   * Sets the main property name.
+   *
+   * @param string|null $name
+   *   The name of the main property, or NULL if there is none.
+   *
+   * @return static
+   *   The object itself for chaining.
+   */
+  public function setMainPropertyName($name) {
+    $this->mainPropertyName = $name;
+    return $this;
+  }
+
+}
diff --git a/core/lib/Drupal/Core/TypedData/Plugin/DataType/ItemList.php b/core/lib/Drupal/Core/TypedData/Plugin/DataType/ItemList.php
index 2e906d0..91865dd 100644
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/ItemList.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/ItemList.php
@@ -8,6 +8,7 @@
 namespace Drupal\Core\TypedData\Plugin\DataType;
 
 use Drupal\Core\TypedData\ComplexDataInterface;
+use Drupal\Core\TypedData\ListDefinition;
 use Drupal\Core\TypedData\ListInterface;
 use Drupal\Core\TypedData\TypedData;
 use Drupal\Core\TypedData\TypedDataInterface;
@@ -35,6 +36,13 @@ class ItemList extends TypedData implements \IteratorAggregate, ListInterface {
   protected $list = array();
 
   /**
+   * {@inheritdoc}
+   */
+  public static function createDataDefinition($data_type) {
+    return ListDefinition::create($data_type);
+  }
+
+  /**
    * Overrides \Drupal\Core\TypedData\TypedData::getValue().
    */
   public function getValue() {
diff --git a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
index ab66442..d08f237 100644
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\TypedData\Plugin\DataType;
 
-use Drupal\Core\TypedData\DataDefinition;
+use Drupal\Core\TypedData\MapDefinition;
 use Drupal\Core\TypedData\TypedData;
 use Drupal\Core\TypedData\ComplexDataInterface;
 
@@ -29,6 +29,13 @@
 class Map extends TypedData implements \IteratorAggregate, ComplexDataInterface {
 
   /**
+   * The data definition.
+   *
+   * @var \Drupal\Core\TypedData\ComplexDataDefinitionInterface
+   */
+  protected $definition;
+
+  /**
    * An array of values for the contained properties.
    *
    * @var array
@@ -36,21 +43,31 @@ class Map extends TypedData implements \IteratorAggregate, ComplexDataInterface
   protected $values = array();
 
   /**
-   * The array of properties, each implementing the TypedDataInterface.
+   * The array of properties.
    *
-   * @var array
+   * @var \Drupal\Core\TypedData\TypedDataInterface[]
    */
   protected $properties = array();
 
   /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
+   * {@inheritdoc}
+   */
+  public static function createDataDefinition($data_type) {
+    return MapDefinition::create($data_type);
+  }
+
+  /**
+   * {@inheritdoc}
    */
   public function getPropertyDefinitions() {
-    $definitions = array();
-    foreach ($this->values as $name => $value) {
-      $definitions[$name] = DataDefinition::create('any');
-    }
-    return $definitions;
+    return $this->definition->getPropertyDefinitions();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinition($name) {
+    return $this->definition->getPropertyDefinition($name);
   }
 
   /**
@@ -128,7 +145,7 @@ public function get($property_name) {
    * Implements \Drupal\Core\TypedData\ComplexDataInterface::set().
    */
   public function set($property_name, $value, $notify = TRUE) {
-    if ($this->getPropertyDefinition($property_name)) {
+    if ($this->definition->getPropertyDefinition($property_name)) {
       $this->get($property_name)->setValue($value, $notify);
     }
     else {
@@ -182,19 +199,6 @@ public function getIterator() {
   }
 
   /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinition().
-   */
-  public function getPropertyDefinition($name) {
-    $definitions = $this->getPropertyDefinitions();
-    if (isset($definitions[$name])) {
-      return $definitions[$name];
-    }
-    else {
-      return FALSE;
-    }
-  }
-
-  /**
    * Implements \Drupal\Core\TypedData\ComplexDataInterface::isEmpty().
    */
   public function isEmpty() {
diff --git a/core/lib/Drupal/Core/TypedData/TypedData.php b/core/lib/Drupal/Core/TypedData/TypedData.php
index 1597c93..2dda8d2 100644
--- a/core/lib/Drupal/Core/TypedData/TypedData.php
+++ b/core/lib/Drupal/Core/TypedData/TypedData.php
@@ -39,6 +39,13 @@
   protected $parent;
 
   /**
+   * {@inheritdoc}
+   */
+  public static function createDataDefinition($data_type) {
+    return DataDefinition::create($data_type);
+  }
+
+  /**
    * Constructs a TypedData object given its definition and context.
    *
    * @param \Drupal\Core\TypedData\DataDefinitionInterface $definition
diff --git a/core/lib/Drupal/Core/TypedData/TypedDataInterface.php b/core/lib/Drupal/Core/TypedData/TypedDataInterface.php
index 4d7b066..bcd7be9 100644
--- a/core/lib/Drupal/Core/TypedData/TypedDataInterface.php
+++ b/core/lib/Drupal/Core/TypedData/TypedDataInterface.php
@@ -15,6 +15,17 @@
 interface TypedDataInterface {
 
   /**
+   * Creates a new data definition object.
+   *
+   * @param string $data_type
+   *   The data type, for which a data definition should be created.
+   *
+   * @return \Drupal\Core\TypedData\DataDefinitionInterface
+   *   A data definition for the given data type.
+   */
+  public static function createDataDefinition($data_type);
+
+  /**
    * Gets the data definition.
    *
    * @return \Drupal\Core\TypedData\DataDefinitionInterface
diff --git a/core/lib/Drupal/Core/TypedData/TypedDataManager.php b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
index e060cd3..3bd17c7 100644
--- a/core/lib/Drupal/Core/TypedData/TypedDataManager.php
+++ b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
@@ -133,6 +133,33 @@ public function create(DataDefinitionInterface $definition, $value = NULL, $name
   }
 
   /**
+   * Creates a new data definition object.
+   *
+   * @param string $data_type
+   *   The data type, for which a data definition should be created.
+   * @param bool $list
+   *   (optional) Whether to define a single item of the given type (FALSE), or
+   *   a list of items (TRUE). Defaults to FALSE.
+   *
+   * @return \Drupal\Core\TypedData\DataDefinitionInterface|\Drupal\Core\TypedData\ListDefinitionInterface
+   *   A data or list definition for the given data type.
+   */
+  public function createDataDefinition($data_type, $list = FALSE) {
+    $type_definition = $this->getDefinition($data_type);
+    if (!isset($type_definition)) {
+      throw new \InvalidArgumentException(format_string('Invalid data type %plugin_id has been given.', array('%plugin_id' => $data_type)));
+    }
+    // A single 'list' item is the same as a list of 'any' items. Always handle
+    // it as the latter, such that the "list" class can always act as a list.
+    if ($data_type == 'list' && !$list) {
+      $data_type = 'any';
+      $list = TRUE;
+    }
+    $class = $list ? $type_definition['list_class'] : $type_definition['class'];
+    return $class::createDataDefinition($data_type);
+  }
+
+  /**
    * Implements \Drupal\Component\Plugin\PluginManagerInterface::getInstance().
    *
    * @param array $options
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index ec6a2cc..1434fea 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -883,7 +883,7 @@ function comment_translation_configuration_element_submit($form, &$form_state) {
 /**
  * Implements hook_entity_load().
  *
- * @see \Drupal\comment\Plugin\Field\FieldType\CommentItem::getPropertyDefinitions()
+ * @see \Drupal\comment\Plugin\Field\FieldType\CommentItem::propertyDefinitions()
  */
 function comment_entity_load($entities, $entity_type) {
   if (!\Drupal::service('comment.manager')->getFields($entity_type)) {
diff --git a/core/modules/comment/lib/Drupal/comment/CommentFieldName.php b/core/modules/comment/lib/Drupal/comment/CommentFieldName.php
index 7912fcc..75d4498 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentFieldName.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentFieldName.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\comment;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\Plugin\Field\FieldType\StringItem;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -16,26 +17,15 @@
 class CommentFieldName extends StringItem {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see self::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('string')
+      ->setLabel(t('String value'))
+      ->setClass('\Drupal\comment\CommentFieldNameValue')
+      ->setComputed(TRUE);
 
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('string')
-        ->setLabel(t('String value'))
-        ->setClass('\Drupal\comment\CommentFieldNameValue')
-        ->setComputed(TRUE);
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 
 }
diff --git a/core/modules/comment/lib/Drupal/comment/Plugin/Field/FieldType/CommentItem.php b/core/modules/comment/lib/Drupal/comment/Plugin/Field/FieldType/CommentItem.php
index a68f8db..df787ad 100644
--- a/core/modules/comment/lib/Drupal/comment/Plugin/Field/FieldType/CommentItem.php
+++ b/core/modules/comment/lib/Drupal/comment/Plugin/Field/FieldType/CommentItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\comment\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 use Drupal\Core\Field\ConfigFieldItemBase;
@@ -33,39 +34,31 @@
 class CommentItem extends ConfigFieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @var array
-   */
-  public static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['status'] = DataDefinition::create('integer')
-        ->setLabel(t('Comment status value'));
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['status'] = DataDefinition::create('integer')
+      ->setLabel(t('Comment status value'));
 
-      static::$propertyDefinitions['cid'] = DataDefinition::create('integer')
-        ->setLabel(t('Last comment ID'));
+    $properties['cid'] = DataDefinition::create('integer')
+      ->setLabel(t('Last comment ID'));
 
-      static::$propertyDefinitions['last_comment_timestamp'] = DataDefinition::create('integer')
-        ->setLabel(t('Last comment timestamp'))
-        ->setDescription(t('The time that the last comment was created.'));
+    $properties['last_comment_timestamp'] = DataDefinition::create('integer')
+      ->setLabel(t('Last comment timestamp'))
+      ->setDescription(t('The time that the last comment was created.'));
 
-      static::$propertyDefinitions['last_comment_name'] = DataDefinition::create('string')
-        ->setLabel(t('Last comment name'))
-        ->setDescription(t('The name of the user posting the last comment.'));
+    $properties['last_comment_name'] = DataDefinition::create('string')
+      ->setLabel(t('Last comment name'))
+      ->setDescription(t('The name of the user posting the last comment.'));
 
-      static::$propertyDefinitions['last_comment_uid'] = DataDefinition::create('integer')
-        ->setLabel(t('Last comment user ID'));
+    $properties['last_comment_uid'] = DataDefinition::create('integer')
+      ->setLabel(t('Last comment user ID'));
 
-      static::$propertyDefinitions['comment_count'] = DataDefinition::create('integer')
-        ->setLabel(t('Number of comments'))
-        ->setDescription(t('The number of comments.'));
-    }
-    return static::$propertyDefinitions;
+    $properties['comment_count'] = DataDefinition::create('integer')
+      ->setLabel(t('Number of comments'))
+      ->setDescription(t('The number of comments.'));
+
+    return $properties;
   }
 
   /**
diff --git a/core/modules/datetime/lib/Drupal/datetime/Plugin/Field/FieldType/DateTimeItem.php b/core/modules/datetime/lib/Drupal/datetime/Plugin/Field/FieldType/DateTimeItem.php
index dc2c201..2d0a501 100644
--- a/core/modules/datetime/lib/Drupal/datetime/Plugin/Field/FieldType/DateTimeItem.php
+++ b/core/modules/datetime/lib/Drupal/datetime/Plugin/Field/FieldType/DateTimeItem.php
@@ -8,6 +8,7 @@
 namespace Drupal\datetime\Plugin\Field\FieldType;
 
 use Drupal\Core\Datetime\DrupalDateTime;
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\PrepareCacheInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
@@ -41,29 +42,20 @@ class DateTimeItem extends ConfigFieldItemBase implements PrepareCacheInterface
   const DATETIME_TYPE_DATETIME = 'datetime';
 
   /**
-   * Field definitions of the contained properties.
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('datetime_iso8601')
-        ->setLabel(t('Date value'));
-
-      static::$propertyDefinitions['date'] = DataDefinition::create('datetime_computed')
-        ->setLabel(t('Computed date'))
-        ->setDescription(t('The computed DateTime object.'))
-        ->setComputed(TRUE)
-        ->setClass('\Drupal\datetime\DateTimeComputed')
-        ->setSetting('date source', 'value');
-    }
-
-    return static::$propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('datetime_iso8601')
+      ->setLabel(t('Date value'));
+
+    $properties['date'] = DataDefinition::create('datetime_computed')
+      ->setLabel(t('Computed date'))
+      ->setDescription(t('The computed DateTime object.'))
+      ->setComputed(TRUE)
+      ->setClass('\Drupal\datetime\DateTimeComputed')
+      ->setSetting('date source', 'value');
+
+    return $properties;
   }
 
   /**
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/ConfigurableEntityReferenceItem.php b/core/modules/entity_reference/lib/Drupal/entity_reference/ConfigurableEntityReferenceItem.php
index 0f708c3..5af3028 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/ConfigurableEntityReferenceItem.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/ConfigurableEntityReferenceItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\entity_reference;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 use Drupal\Core\Field\ConfigEntityReferenceItemBase;
@@ -27,40 +28,25 @@
 class ConfigurableEntityReferenceItem extends ConfigEntityReferenceItemBase implements ConfigFieldItemInterface {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see ConfigurableEntityReferenceItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    $settings = $this->definition->getSettings();
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $settings = $field_definition->getSettings();
     $target_type = $settings['target_type'];
 
-    // Definitions vary by entity type and bundle, so key them accordingly.
-    $key = $target_type . ':';
-    $key .= isset($settings['target_bundle']) ? $settings['target_bundle'] : '';
-
-    if (!isset(static::$propertyDefinitions[$key])) {
-      // Call the parent to define the target_id and entity properties.
-      parent::getPropertyDefinitions();
-
-      // Only add the revision ID property if the target entity type supports
-      // revisions.
-      $target_type_info = \Drupal::entityManager()->getDefinition($target_type);
-      if ($target_type_info->hasKey('revision') && $target_type_info->getRevisionTable()) {
-        static::$propertyDefinitions[$key]['revision_id'] = DataDefinition::create('integer')
-          ->setLabel(t('Revision ID'))
-          ->setConstraints(array('Range' => array('min' => 0)));
-      }
+    // Call the parent to define the target_id and entity properties.
+    $properties = parent::propertyDefinitions($field_definition);
+
+    // Only add the revision ID property if the target entity type supports
+    // revisions.
+    $target_type_info = \Drupal::entityManager()->getDefinition($target_type);
+    if ($target_type_info->hasKey('revision') && $target_type_info->getRevisionTable()) {
+      $properties['revision_id'] = DataDefinition::create('integer')
+        ->setLabel(t('Revision ID'))
+        ->setConstraints(array('Range' => array('min' => 0)));
     }
 
-    return static::$propertyDefinitions[$key];
+    return $properties;
   }
 
   /**
diff --git a/core/modules/field/lib/Drupal/field/Entity/Field.php b/core/modules/field/lib/Drupal/field/Entity/Field.php
index 098d83f..5689ab5 100644
--- a/core/modules/field/lib/Drupal/field/Entity/Field.php
+++ b/core/modules/field/lib/Drupal/field/Entity/Field.php
@@ -11,7 +11,7 @@
 use Drupal\Core\Config\Entity\ConfigEntityBase;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityStorageControllerInterface;
-use Drupal\Core\TypedData\DataDefinition;
+use Drupal\Core\Field\FieldItemDefinition;
 use Drupal\field\FieldException;
 use Drupal\field\FieldInterface;
 
@@ -192,6 +192,15 @@ class Field extends ConfigEntityBase implements FieldInterface {
   public $original = NULL;
 
   /**
+   * An array of field property definitions.
+   *
+   * @var \Drupal\Core\TypedData\DataDefinitionInterface[]
+   *
+   * @see \Drupal\Core\TypedData\ComplexDataDefinitionInterface::getPropertyDefinitions()
+   */
+  protected $propertyDefinitions;
+
+  /**
    * The data definition of a field item.
    *
    * @var \Drupal\Core\TypedData\DataDefinition
@@ -551,14 +560,6 @@ public function getSetting($setting_name) {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyNames() {
-    $schema = $this->getSchema();
-    return array_keys($schema['columns']);
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function isTranslatable() {
     return $this->translatable;
   }
@@ -754,10 +755,65 @@ public function getConstraint($constraint_name) {
    */
   public function getItemDefinition() {
     if (!isset($this->itemDefinition)) {
-      $this->itemDefinition = DataDefinition::create('field_item:' . $this->type)
+      $this->itemDefinition = FieldItemDefinition::create($this)
         ->setSettings($this->getSettings());
     }
     return $this->itemDefinition;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinition($name) {
+    if (!isset($this->propertyDefinitions)) {
+      $this->getPropertyDefinitions();
+    }
+    if (isset($this->propertyDefinitions[$name])) {
+      return $this->propertyDefinitions[$name];
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinitions() {
+    if (!isset($this->propertyDefinitions)) {
+      $class = $this->getFieldItemClass();
+      $this->propertyDefinitions = $class::propertyDefinitions($this);
+    }
+    return $this->propertyDefinitions;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyNames() {
+    return array_keys($this->getPropertyDefinitions());
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMainPropertyName() {
+    $class = $this->getFieldItemClass();
+    return $class::getMainPropertyName();
+  }
+
+  /**
+   * Helper to retrieve the field item class.
+   *
+   * @todo: Remove once getClass() adds in defaults. See
+   * https://drupal.org/node/2116341.
+   */
+  protected function getFieldItemClass() {
+    if ($class = $this->getItemDefinition()->getClass()) {
+      return $class;
+    }
+    else {
+      $type_definition = \Drupal::typedDataManager()
+        ->getDefinition($this->getItemDefinition()->getDataType());
+      return $type_definition['class'];
+    }
+  }
+
 }
diff --git a/core/modules/field/lib/Drupal/field/Entity/FieldInstance.php b/core/modules/field/lib/Drupal/field/Entity/FieldInstance.php
index 7c2e381..2fc1ddd 100644
--- a/core/modules/field/lib/Drupal/field/Entity/FieldInstance.php
+++ b/core/modules/field/lib/Drupal/field/Entity/FieldInstance.php
@@ -10,6 +10,7 @@
 use Drupal\Core\Config\Entity\ConfigEntityBase;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityStorageControllerInterface;
+use Drupal\Core\Field\FieldItemDefinition;
 use Drupal\field\FieldException;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInstanceInterface;
@@ -496,14 +497,6 @@ public function getSetting($setting_name) {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyNames() {
-    $schema = $this->field->getSchema();
-    return array_keys($schema['columns']);
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function isTranslatable() {
     return $this->field->translatable;
   }
@@ -676,9 +669,37 @@ public function getConstraint($constraint_name) {
    */
   public function getItemDefinition() {
     if (!isset($this->itemDefinition)) {
-      $this->itemDefinition = DataDefinition::create('field_item:' . $this->field->type)
+      $this->itemDefinition = FieldItemDefinition::create($this)
         ->setSettings($this->getSettings());
     }
     return $this->itemDefinition;
   }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinition($name) {
+    return $this->field->getPropertyDefinition($name);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyDefinitions() {
+    return $this->field->getPropertyDefinitions();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPropertyNames() {
+    return $this->field->getPropertyNames();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMainPropertyName() {
+    return $this->field->getMainPropertyName();
+  }
 }
diff --git a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/HiddenTestItem.php b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/HiddenTestItem.php
index d3597fd..700efde 100644
--- a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/HiddenTestItem.php
+++ b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/HiddenTestItem.php
@@ -7,8 +7,8 @@
 
 namespace Drupal\field_test\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
-use Drupal\field_test\Plugin\Field\FieldType\TestItem;
 
 /**
  * Defines the 'hidden_test' entity field item.
@@ -25,23 +25,13 @@
 class HiddenTestItem extends TestItem {
 
   /**
-   * Property definitions of the contained properties.
-   *
-   * @see TestItem::getPropertyDefinitions()
-   *
-   * @var array
+   * {@inheritdoc}
    */
-  static $propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('integer')
+      ->setLabel(t('Test integer value'));
 
-  /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
-   */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('integer')
-        ->setLabel(t('Test integer value'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 
 }
diff --git a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/ShapeItem.php b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/ShapeItem.php
index fedd03c..f20940e 100644
--- a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/ShapeItem.php
+++ b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/ShapeItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\field_test\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 use Drupal\Core\Field\ConfigFieldItemBase;
@@ -28,26 +29,16 @@
 class ShapeItem extends ConfigFieldItemBase {
 
   /**
-   * Property definitions of the contained properties.
-   *
-   * @see ShapeItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['shape'] = DataDefinition::create('string')
-        ->setLabel(t('Shape'));
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['shape'] = DataDefinition::create('string')
+      ->setLabel(t('Shape'));
 
-      static::$propertyDefinitions['color'] = DataDefinition::create('string')
-        ->setLabel(t('Color'));
-    }
-    return static::$propertyDefinitions;
+    $properties['color'] = DataDefinition::create('string')
+      ->setLabel(t('Color'));
+
+    return $properties;
   }
 
   /**
diff --git a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/TestItem.php b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/TestItem.php
index ed8f38a..80b70be 100644
--- a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/TestItem.php
+++ b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/Field/FieldType/TestItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\field_test\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\PrepareCacheInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
@@ -35,23 +36,13 @@
 class TestItem extends ConfigFieldItemBase implements PrepareCacheInterface {
 
   /**
-   * Property definitions of the contained properties.
-   *
-   * @see TestItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('integer')
-        ->setLabel(t('Test integer value'));
-    }
-    return static::$propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('integer')
+      ->setLabel(t('Test integer value'));
+
+    return $properties;
   }
 
   /**
diff --git a/core/modules/file/lib/Drupal/file/Plugin/Field/FieldType/FileItem.php b/core/modules/file/lib/Drupal/file/Plugin/Field/FieldType/FileItem.php
index 188ae85..3167780 100644
--- a/core/modules/file/lib/Drupal/file/Plugin/Field/FieldType/FileItem.php
+++ b/core/modules/file/lib/Drupal/file/Plugin/Field/FieldType/FileItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\file\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
@@ -20,6 +21,7 @@
  *   label = @Translation("File"),
  *   description = @Translation("This field stores the ID of a file as an integer value."),
  *   settings = {
+ *     "target_type" = "file",
  *     "display_field" = "0",
  *     "display_default" = "0",
  *     "uri_scheme" = ""
@@ -38,15 +40,6 @@
 class FileItem extends EntityReferenceItem implements ConfigFieldItemInterface {
 
   /**
-   * Property definitions of the contained properties.
-   *
-   * @see FileItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
   public static function schema(FieldInterface $field) {
@@ -87,19 +80,16 @@ public static function schema(FieldInterface $field) {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    $this->definition->setSetting('target_type', 'file');
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties = parent::propertyDefinitions($field_definition);
 
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions = parent::getPropertyDefinitions();
+    $properties['display'] = DataDefinition::create('boolean')
+      ->setLabel(t('Flag to control whether this file should be displayed when viewing content'));
 
-      static::$propertyDefinitions['display'] = DataDefinition::create('boolean')
-        ->setLabel(t('Flag to control whether this file should be displayed when viewing content'));
+    $properties['description'] = DataDefinition::create('string')
+      ->setLabel(t('A description of the file'));
 
-      static::$propertyDefinitions['description'] = DataDefinition::create('string')
-        ->setLabel(t('A description of the file'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 
   /**
diff --git a/core/modules/image/lib/Drupal/image/Plugin/Field/FieldType/ImageItem.php b/core/modules/image/lib/Drupal/image/Plugin/Field/FieldType/ImageItem.php
index 59e464c..c20b268 100644
--- a/core/modules/image/lib/Drupal/image/Plugin/Field/FieldType/ImageItem.php
+++ b/core/modules/image/lib/Drupal/image/Plugin/Field/FieldType/ImageItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\image\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 use Drupal\file\Plugin\Field\FieldType\FileItem;
@@ -19,6 +20,7 @@
  *   label = @Translation("Image"),
  *   description = @Translation("This field stores the ID of an image file as an integer value."),
  *   settings = {
+ *     "target_type" = "file",
  *     "uri_scheme" = "",
  *     "default_image" = {
  *       "fid" = NULL,
@@ -117,25 +119,22 @@ public static function schema(FieldInterface $field) {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    $this->definition->setSetting('target_type', 'file');
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties = parent::propertyDefinitions($field_definition);
 
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions = parent::getPropertyDefinitions();
+    $properties['alt'] = DataDefinition::create('string')
+      ->setLabel(t("Alternative image text, for the image's 'alt' attribute."));
 
-      static::$propertyDefinitions['alt'] = DataDefinition::create('string')
-        ->setLabel(t("Alternative image text, for the image's 'alt' attribute."));
+    $properties['title'] = DataDefinition::create('string')
+      ->setLabel(t("Image title text, for the image's 'title' attribute."));
 
-      static::$propertyDefinitions['title'] = DataDefinition::create('string')
-        ->setLabel(t("Image title text, for the image's 'title' attribute."));
+    $properties['width'] = DataDefinition::create('integer')
+      ->setLabel(t('The width of the image in pixels.'));
 
-      static::$propertyDefinitions['width'] = DataDefinition::create('integer')
-        ->setLabel(t('The width of the image in pixels.'));
+    $properties['height'] = DataDefinition::create('integer')
+      ->setLabel(t('The height of the image in pixels.'));
 
-      static::$propertyDefinitions['height'] = DataDefinition::create('integer')
-        ->setLabel(t('The height of the image in pixels.'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 
   /**
diff --git a/core/modules/link/lib/Drupal/link/Plugin/Field/FieldType/LinkItem.php b/core/modules/link/lib/Drupal/link/Plugin/Field/FieldType/LinkItem.php
index 3c914ae..db5441e 100644
--- a/core/modules/link/lib/Drupal/link/Plugin/Field/FieldType/LinkItem.php
+++ b/core/modules/link/lib/Drupal/link/Plugin/Field/FieldType/LinkItem.php
@@ -8,7 +8,9 @@
 namespace Drupal\link\Plugin\Field\FieldType;
 
 use Drupal\Core\Field\ConfigFieldItemBase;
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
+use Drupal\Core\TypedData\MapDefinition;
 use Drupal\field\FieldInterface;
 
 /**
@@ -28,27 +30,19 @@
 class LinkItem extends ConfigFieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['url'] = DataDefinition::create('uri')
-        ->setLabel(t('URL'));
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['url'] = DataDefinition::create('uri')
+      ->setLabel(t('URL'));
+
+    $properties['title'] = DataDefinition::create('string')
+      ->setLabel(t('Link text'));
 
-      static::$propertyDefinitions['title'] = DataDefinition::create('string')
-        ->setLabel(t('Link text'));
+    $properties['attributes'] = MapDefinition::create('map')
+      ->setLabel(t('Attributes'));
 
-      static::$propertyDefinitions['attributes'] = DataDefinition::create('map')
-        ->setLabel(t('Attributes'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 
   /**
diff --git a/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/DecimalItem.php b/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/DecimalItem.php
index 16353db..6083706 100644
--- a/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/DecimalItem.php
+++ b/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/DecimalItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\number\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 use Drupal\Component\Utility\MapArray;
@@ -37,12 +38,11 @@ class DecimalItem extends NumberItemBase {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('string')
-        ->setLabel(t('Decimal value'));
-    }
-    return static::$propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('string')
+      ->setLabel(t('Decimal value'));
+
+    return $properties;
   }
 
   /**
diff --git a/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/FloatItem.php b/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/FloatItem.php
index 88ee07f..ccbe819 100644
--- a/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/FloatItem.php
+++ b/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/FloatItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\number\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 
@@ -32,12 +33,11 @@ class FloatItem extends NumberItemBase {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('float')
-        ->setLabel(t('Float value'));
-    }
-    return static::$propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('float')
+      ->setLabel(t('Float value'));
+
+    return $properties;
   }
 
   /**
diff --git a/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/IntegerItem.php b/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/IntegerItem.php
index dfe35f6..a8cf839 100644
--- a/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/IntegerItem.php
+++ b/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/IntegerItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\number\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 
@@ -32,12 +33,11 @@ class IntegerItem extends NumberItemBase {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('integer')
-        ->setLabel(t('Integer value'));
-    }
-    return static::$propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('integer')
+      ->setLabel(t('Integer value'));
+
+    return $properties;
   }
 
   /**
diff --git a/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/NumberItemBase.php b/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/NumberItemBase.php
index e8630be..c8d8ac1 100644
--- a/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/NumberItemBase.php
+++ b/core/modules/number/lib/Drupal/number/Plugin/Field/FieldType/NumberItemBase.php
@@ -15,13 +15,6 @@
 abstract class NumberItemBase extends ConfigFieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
   public function instanceSettingsForm(array $form, array &$form_state) {
diff --git a/core/modules/options/lib/Drupal/options/Type/ListFloatItem.php b/core/modules/options/lib/Drupal/options/Type/ListFloatItem.php
index 6b18833..12d0c85 100644
--- a/core/modules/options/lib/Drupal/options/Type/ListFloatItem.php
+++ b/core/modules/options/lib/Drupal/options/Type/ListFloatItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\options\Type;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\Plugin\Field\FieldType\LegacyConfigFieldItem;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -16,23 +17,13 @@
 class ListFloatItem extends LegacyConfigFieldItem {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see FloatItem::getPropertyDefinitions()
-   *
-   * @var array
+   * {@inheritdoc}
    */
-  static $propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('float')
+      ->setLabel(t('Float value'));
 
-  /**
-   * Implements ComplexDataInterface::getPropertyDefinitions().
-   */
-  public function getPropertyDefinitions() {
-
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('float')
-        ->setLabel(t('Float value'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
+
 }
diff --git a/core/modules/options/lib/Drupal/options/Type/ListIntegerItem.php b/core/modules/options/lib/Drupal/options/Type/ListIntegerItem.php
index 72ed788..cd9bc81 100644
--- a/core/modules/options/lib/Drupal/options/Type/ListIntegerItem.php
+++ b/core/modules/options/lib/Drupal/options/Type/ListIntegerItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\options\Type;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\Plugin\Field\FieldType\LegacyConfigFieldItem;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -16,23 +17,13 @@
 class ListIntegerItem extends LegacyConfigFieldItem {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see IntegerItem::getPropertyDefinitions()
-   *
-   * @var array
+   * {@inheritdoc}
    */
-  static $propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('integer')
+      ->setLabel(t('Integer value'));
 
-  /**
-   * Implements ComplexDataInterface::getPropertyDefinitions().
-   */
-  public function getPropertyDefinitions() {
-
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('integer')
-        ->setLabel(t('Integer value'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
+
 }
diff --git a/core/modules/options/lib/Drupal/options/Type/ListTextItem.php b/core/modules/options/lib/Drupal/options/Type/ListTextItem.php
index b66d355..41ea0db 100644
--- a/core/modules/options/lib/Drupal/options/Type/ListTextItem.php
+++ b/core/modules/options/lib/Drupal/options/Type/ListTextItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\options\Type;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\Plugin\Field\FieldType\LegacyConfigFieldItem;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -16,24 +17,13 @@
 class ListTextItem extends LegacyConfigFieldItem {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see TextItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * Implements ComplexDataInterface::getPropertyDefinitions().
    */
-  public function getPropertyDefinitions() {
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('string')
+      ->setLabel(t('Text value'));
 
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('string')
-        ->setLabel(t('Text value'));
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 
 }
diff --git a/core/modules/path/lib/Drupal/path/Plugin/Field/FieldType/PathItem.php b/core/modules/path/lib/Drupal/path/Plugin/Field/FieldType/PathItem.php
index 601bc0b..c89ea05 100644
--- a/core/modules/path/lib/Drupal/path/Plugin/Field/FieldType/PathItem.php
+++ b/core/modules/path/lib/Drupal/path/Plugin/Field/FieldType/PathItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\path\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemBase;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -23,26 +24,16 @@
 class PathItem extends FieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see PathItem::getPropertyDefinitions()
-   *
-   * @var array
+   * {@inheritdoc}
    */
-  static $propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['alias'] = DataDefinition::create('string')
+      ->setLabel(t('Path alias'));
 
-  /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
-   */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['alias'] = DataDefinition::create('string')
-        ->setLabel(t('Path alias'));
-
-      static::$propertyDefinitions['pid'] = DataDefinition::create('string')
-        ->setLabel(t('Path id'));
-    }
-    return static::$propertyDefinitions;
+    $properties['pid'] = DataDefinition::create('string')
+      ->setLabel(t('Path id'));
+
+    return $properties;
   }
 
 }
diff --git a/core/modules/shortcut/lib/Drupal/shortcut/ShortcutPath.php b/core/modules/shortcut/lib/Drupal/shortcut/ShortcutPath.php
index 885d304..6e235e5 100644
--- a/core/modules/shortcut/lib/Drupal/shortcut/ShortcutPath.php
+++ b/core/modules/shortcut/lib/Drupal/shortcut/ShortcutPath.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\shortcut;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\Plugin\Field\FieldType\StringItem;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -16,25 +17,14 @@
 class ShortcutPath extends StringItem {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @see self::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('string')
-        ->setLabel(t('String value'))
-        ->setComputed(TRUE)
-        ->setClass('\Drupal\shortcut\ShortcutPathValue');
-    }
-    return static::$propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('string')
+      ->setLabel(t('String value'))
+      ->setComputed(TRUE)
+      ->setClass('\Drupal\shortcut\ShortcutPathValue');
+    return $properties;
   }
 
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/TypedData/MetadataTest.php b/core/modules/system/lib/Drupal/system/Tests/TypedData/MetadataTest.php
new file mode 100644
index 0000000..520c3c3
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/TypedData/MetadataTest.php
@@ -0,0 +1,148 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\TypedData\MetadataTest.
+ */
+
+namespace Drupal\system\Tests\TypedData;
+
+use Drupal\Core\Field\FieldDefinition;
+use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Core\TypedData\ComplexDataDefinitionInterface;
+use Drupal\Core\TypedData\DataDefinition;
+use Drupal\Core\TypedData\DataDefinitionInterface;
+use Drupal\Core\TypedData\ListDefinition;
+use Drupal\Core\TypedData\ListDefinitionInterface;
+use Drupal\Core\TypedData\MapDefinition;
+use Drupal\simpletest\DrupalUnitTestBase;
+
+/**
+ * Tests deriving metadata of core data types.
+ */
+class MetadataTest extends DrupalUnitTestBase {
+
+  /**
+   * The typed data manager to use.
+   *
+   * @var \Drupal\Core\TypedData\TypedDataManager
+   */
+  protected $typedDataManager;
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('system');
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Metadata',
+      'description' => 'Tests reading and deriving metadata of core data types.',
+      'group' => 'Typed Data API',
+    );
+  }
+
+  public function setUp() {
+    parent::setup();
+    $this->typedDataManager = $this->container->get('typed_data_manager');
+  }
+
+  /**
+   * Tests deriving metadata about list items.
+   */
+  public function testLists() {
+    $list = ListDefinition::create('string');
+    $this->assertTrue($list instanceof ListDefinitionInterface);
+    $item = $list->getItemDefinition();
+    $this->assertTrue($item instanceof DataDefinitionInterface);
+    $this->assertEqual($item->getDataType(), 'string');
+
+    // Test using the definition factory.
+    $list2 = $this->typedDataManager->createDataDefinition('string', TRUE);
+    $this->assertTrue($list2 instanceof ListDefinitionInterface);
+    $this->assertEqual($list, $list2);
+
+    // Test creating a single list item, which is the same as a list of any
+    // items.
+    $list = $this->typedDataManager->createDataDefinition('list');
+    $this->assertTrue($list instanceof ListDefinitionInterface);
+    $this->assertEqual($list->getDataType(), 'list');
+    $this->assertEqual($list->getItemDefinition()->getDataType(), 'any');
+  }
+
+  /**
+   * Tests deriving metadata about maps.
+   */
+  public function testMaps() {
+    $map = MapDefinition::create()
+      ->setPropertyDefinition('one', DataDefinition::create('string'))
+      ->setPropertyDefinition('two', DataDefinition::create('string'))
+      ->setPropertyDefinition('three', DataDefinition::create('string'));
+
+    $this->assertTrue($map instanceof ComplexDataDefinitionInterface);
+
+    // Test retrieving metadata about contained properties.
+    $this->assertEqual(array_keys($map->getPropertyDefinitions()), array('one', 'two', 'three'));
+    $this->assertEqual($map->getPropertyDefinition('one')->getDataType(), 'string');
+    $this->assertNull($map->getMainPropertyName());
+    $this->assertNull($map->getPropertyDefinition('invalid'));
+
+    // Test using the definition factory.
+    $map2 = $this->typedDataManager->createDataDefinition('map');
+    $this->assertTrue($map2 instanceof ComplexDataDefinitionInterface);
+    $map2->setPropertyDefinition('one', DataDefinition::create('string'))
+      ->setPropertyDefinition('two', DataDefinition::create('string'))
+      ->setPropertyDefinition('three', DataDefinition::create('string'));
+    $this->assertEqual($map, $map2);
+  }
+
+  /**
+   * Tests deriving metadata about fields.
+   */
+  public function testFields() {
+    $field = FieldDefinition::create('integer');
+    // Fields are lists of complex data.
+    $this->assertTrue($field instanceof ListDefinitionInterface);
+    $this->assertFalse($field instanceof ComplexDataDefinitionInterface);
+    $field_item = $field->getItemDefinition();
+    $this->assertFalse($field_item instanceof ListDefinitionInterface);
+    $this->assertTrue($field_item instanceof ComplexDataDefinitionInterface);
+
+    // Derive metadata about field item properties.
+    $this->assertEqual(array_keys($field_item->getPropertyDefinitions()), array('value'));
+    $this->assertEqual($field_item->getPropertyDefinition('value')->getDataType(), 'integer');
+    $this->assertEqual($field_item->getMainPropertyName(), 'value');
+    $this->assertNull($field_item->getPropertyDefinition('invalid'));
+
+    // To ease access of field item property metadata, field definitions make
+    // metadata about field item properties on the field level as well.
+    $this->assertTrue($field instanceof FieldDefinitionInterface);
+    $this->assertEqual(array_keys($field->getPropertyDefinitions()), array('value'));
+    $this->assertEqual($field->getPropertyDefinition('value')->getDataType(), 'integer');
+    $this->assertEqual($field->getMainPropertyName(), 'value');
+    $this->assertNull($field->getPropertyDefinition('invalid'));
+
+    // Test using the definition factory for field item lists and field items.
+    $field_item2 = $this->typedDataManager->createDataDefinition('field_item:integer');
+    $this->assertFalse($field_item2 instanceof ListDefinitionInterface);
+    $this->assertTrue($field_item2 instanceof ComplexDataDefinitionInterface);
+    // Comparison should ignore the internal static cache, so compare the
+    // serialized objects instead.
+    $this->assertEqual(serialize($field_item), serialize($field_item2));
+
+    $field2 = $this->typedDataManager->createDataDefinition('field_item:integer', TRUE);
+    $this->assertTrue($field2 instanceof ListDefinitionInterface);
+    $this->assertFalse($field2 instanceof ComplexDataDefinitionInterface);
+    $this->assertEqual(serialize($field), serialize($field2));
+  }
+
+  /**
+   * Tests deriving metadata about entities.
+   */
+  public function testEntities() {
+    // @todo: Implement.
+  }
+
+}
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 eeb6bb5..985f401 100644
--- a/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
@@ -10,6 +10,8 @@
 use Drupal\Core\Field\FieldDefinition;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\Core\TypedData\ListDefinition;
+use Drupal\Core\TypedData\MapDefinition;
+use Drupal\Core\TypedData\Plugin\DataType\Map;
 use Drupal\simpletest\DrupalUnitTestBase;
 use Drupal\Core\Datetime\DrupalDateTime;
 
@@ -410,9 +412,12 @@ public function testTypedDataMaps() {
       'two' => 'zwei',
       'three' => 'drei',
     );
-    $typed_data = $this->createTypedData(array(
-      'type' => 'map',
-    ), $value);
+    $definition = MapDefinition::create('map')
+      ->setPropertyDefinition('one', DataDefinition::create('string'))
+      ->setPropertyDefinition('two', DataDefinition::create('string'))
+      ->setPropertyDefinition('three', DataDefinition::create('string'));
+
+    $typed_data = $this->createTypedData($definition, $value);
 
     // Test iterating.
     $count = 0;
@@ -424,9 +429,9 @@ public function testTypedDataMaps() {
 
     // Test retrieving metadata.
     $this->assertEqual(array_keys($typed_data->getPropertyDefinitions()), array_keys($value));
-    $definition = $typed_data->getPropertyDefinition('one');
-    $this->assertEqual($definition->getDataType(), 'any');
-    $this->assertFalse($typed_data->getPropertyDefinition('invalid'));
+    $definition = $typed_data->getDefinition()->getPropertyDefinition('one');
+    $this->assertEqual($definition->getDataType(), 'string');
+    $this->assertNull($typed_data->getDefinition()->getPropertyDefinition('invalid'));
 
     // Test getting and setting properties.
     $this->assertEqual($typed_data->get('one')->getValue(), 'eins');
@@ -450,8 +455,11 @@ public function testTypedDataMaps() {
     $this->assertEqual($typed_data->get('two')->getValue(), 'zwei');
     $this->assertEqual($typed_data->get('three')->getValue(), 'drei');
 
+    // Test setting a not defined property. It shouldn't show up in the
+    // properties, but be kept in the values.
     $typed_data->setValue(array('foo' => 'bar'));
-    $this->assertEqual(array_keys($typed_data->getProperties()), array('foo'));
+    $this->assertEqual(array_keys($typed_data->getProperties()), array('one', 'two', 'three'));
+    $this->assertEqual(array_keys($typed_data->getValue()), array('foo', 'one', 'two', 'three'));
 
     // Test getting the string representation.
     $typed_data->setValue(array('one' => 'eins', 'two' => '', 'three' => 'drei'));
@@ -492,10 +500,11 @@ public function testTypedDataMaps() {
       $this->pass('Exception thrown:' . $e->getMessage());
     }
 
-    // Test adding a new entry to the map.
+    // Test adding a new property to the map.
+    $typed_data->getDefinition()->setPropertyDefinition('zero', DataDefinition::create('any'));
     $typed_data->set('zero', 'null');
     $this->assertEqual($typed_data->get('zero')->getValue(), 'null');
-    $definition = $typed_data->getPropertyDefinition('zero');
+    $definition = $typed_data->get('zero')->getDefinition();
     $this->assertEqual($definition->getDataType(), 'any', 'Definition for a new map entry returned.');
   }
 
diff --git a/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/Field/FieldType/TaxonomyTermReferenceItem.php b/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/Field/FieldType/TaxonomyTermReferenceItem.php
index 13025de..f637c98 100644
--- a/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/Field/FieldType/TaxonomyTermReferenceItem.php
+++ b/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/Field/FieldType/TaxonomyTermReferenceItem.php
@@ -21,6 +21,7 @@
  *   label = @Translation("Term Reference"),
  *   description = @Translation("This field stores a reference to a taxonomy term."),
  *   settings = {
+ *     "target_type" = "taxonomy_term",
  *     "options_list_callback" = NULL,
  *     "allowed_values" = {
  *       {
@@ -89,14 +90,6 @@ public function getSettableOptions(AccountInterface $account = NULL) {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    $this->definition['settings']['target_type'] = 'taxonomy_term';
-    return parent::getPropertyDefinitions();
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public static function schema(FieldInterface $field) {
     return array(
       'columns' => array(
diff --git a/core/modules/telephone/lib/Drupal/telephone/Plugin/Field/FieldType/TelephoneItem.php b/core/modules/telephone/lib/Drupal/telephone/Plugin/Field/FieldType/TelephoneItem.php
index e55fd52..dd23ca3 100644
--- a/core/modules/telephone/lib/Drupal/telephone/Plugin/Field/FieldType/TelephoneItem.php
+++ b/core/modules/telephone/lib/Drupal/telephone/Plugin/Field/FieldType/TelephoneItem.php
@@ -8,6 +8,7 @@
 namespace Drupal\telephone\Plugin\Field\FieldType;
 
 use Drupal\Core\Field\ConfigFieldItemBase;
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 
@@ -25,13 +26,6 @@
 class TelephoneItem extends ConfigFieldItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
   public static function schema(FieldInterface $field) {
@@ -49,12 +43,11 @@ public static function schema(FieldInterface $field) {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('string')
-        ->setLabel(t('Telephone number'));
-    }
-    return static::$propertyDefinitions;
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('string')
+      ->setLabel(t('Telephone number'));
+
+    return $properties;
   }
 
   /**
diff --git a/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextItemBase.php b/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextItemBase.php
index 90d86c2..643b5b7 100644
--- a/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextItemBase.php
+++ b/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextItemBase.php
@@ -8,6 +8,7 @@
 namespace Drupal\text\Plugin\Field\FieldType;
 
 use Drupal\Core\Field\ConfigFieldItemBase;
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\PrepareCacheInterface;
 use Drupal\Core\TypedData\DataDefinition;
 
@@ -17,31 +18,23 @@
 abstract class TextItemBase extends ConfigFieldItemBase implements PrepareCacheInterface {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions['value'] = DataDefinition::create('string')
-        ->setLabel(t('Text value'));
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties['value'] = DataDefinition::create('string')
+      ->setLabel(t('Text value'));
 
-      static::$propertyDefinitions['format'] = DataDefinition::create('filter_format')
-        ->setLabel(t('Text format'));
+    $properties['format'] = DataDefinition::create('filter_format')
+      ->setLabel(t('Text format'));
 
-      static::$propertyDefinitions['processed'] = DataDefinition::create('string')
-        ->setLabel(t('Processed text'))
-        ->setDescription(t('The text value with the text format applied.'))
-        ->setComputed(TRUE)
-        ->setClass('\Drupal\text\TextProcessed')
-        ->setSetting('text source', 'value');
-    }
-    return static::$propertyDefinitions;
+    $properties['processed'] = DataDefinition::create('string')
+      ->setLabel(t('Processed text'))
+      ->setDescription(t('The text value with the text format applied.'))
+      ->setComputed(TRUE)
+      ->setClass('\Drupal\text\TextProcessed')
+      ->setSetting('text source', 'value');
+
+    return $properties;
   }
 
   /**
diff --git a/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextWithSummaryItem.php b/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextWithSummaryItem.php
index 1efad43..1e0b7c7 100644
--- a/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextWithSummaryItem.php
+++ b/core/modules/text/lib/Drupal/text/Plugin/Field/FieldType/TextWithSummaryItem.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\text\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 
@@ -28,30 +29,22 @@
 class TextWithSummaryItem extends TextItemBase {
 
   /**
-   * Definitions of the contained properties.
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
    * {@inheritdoc}
    */
-  public function getPropertyDefinitions() {
-    if (!isset(static::$propertyDefinitions)) {
-      static::$propertyDefinitions = parent::getPropertyDefinitions();
+  public static function propertyDefinitions(FieldDefinitionInterface $field_definition) {
+    $properties = parent::propertyDefinitions($field_definition);
+
+    $properties['summary'] = DataDefinition::create('string')
+      ->setLabel(t('Summary text value'));
 
-      static::$propertyDefinitions['summary'] = DataDefinition::create('string')
-        ->setLabel(t('Summary text value'));
+    $properties['summary_processed'] = DataDefinition::create('string')
+      ->setLabel(t('Processed summary text'))
+      ->setDescription(t('The summary text value with the text format applied.'))
+      ->setComputed(TRUE)
+      ->setClass('\Drupal\text\TextProcessed')
+      ->setSetting('text source', 'summary');
 
-      static::$propertyDefinitions['summary_processed'] = DataDefinition::create('string')
-        ->setLabel(t('Processed summary text'))
-        ->setDescription(t('The summary text value with the text format applied.'))
-        ->setComputed(TRUE)
-        ->setClass('\Drupal\text\TextProcessed')
-        ->setSetting('text source', 'summary');
-    }
-    return static::$propertyDefinitions;
+    return $properties;
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/Core/Entity/FieldDefinitionTest.php b/core/tests/Drupal/Tests/Core/Entity/FieldDefinitionTest.php
index 2982685..2854045 100644
--- a/core/tests/Drupal/Tests/Core/Entity/FieldDefinitionTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/FieldDefinitionTest.php
@@ -57,7 +57,7 @@ protected function setUp() {
    * Tests field name methods.
    */
   public function testFieldName() {
-    $definition = new FieldDefinition();
+    $definition = FieldDefinition::create('integer');
     $field_name = $this->randomName();
     $definition->setName($field_name);
     $this->assertEquals($field_name, $definition->getName());
@@ -67,7 +67,7 @@ public function testFieldName() {
    * Tests field label methods.
    */
   public function testFieldLabel() {
-    $definition = new FieldDefinition();
+    $definition = FieldDefinition::create('integer');
     $label = $this->randomName();
     $definition->setLabel($label);
     $this->assertEquals($label, $definition->getLabel());
@@ -77,7 +77,7 @@ public function testFieldLabel() {
    * Tests field description methods.
    */
   public function testFieldDescription() {
-    $definition = new FieldDefinition();
+    $definition = FieldDefinition::create('integer');
     $description = $this->randomName();
     $definition->setDescription($description);
     $this->assertEquals($description, $definition->getDescription());
@@ -96,7 +96,7 @@ public function testFieldType() {
    * Tests field settings methods.
    */
   public function testFieldSettings() {
-    $definition = new FieldDefinition();
+    $definition = FieldDefinition::create('integer');
     $setting = $this->randomName();
     $value = $this->randomName();
     $definition->setSetting($setting, $value);
@@ -108,7 +108,7 @@ public function testFieldSettings() {
    * Tests field default value.
    */
   public function testFieldDefaultValue() {
-    $definition = new FieldDefinition();
+    $definition = FieldDefinition::create('integer');
     $setting = 'default_value';
     $value = $this->randomName();
     $definition->setSetting($setting, $value);
@@ -122,7 +122,7 @@ public function testFieldDefaultValue() {
    * Tests field translatable methods.
    */
   public function testFieldTranslatable() {
-    $definition = new FieldDefinition();
+    $definition = FieldDefinition::create('integer');
     $this->assertFalse($definition->isTranslatable());
     $definition->setTranslatable(TRUE);
     $this->assertTrue($definition->isTranslatable());
@@ -134,7 +134,7 @@ public function testFieldTranslatable() {
    * Tests field cardinality.
    */
   public function testFieldCardinality() {
-    $definition = new FieldDefinition();
+    $definition = FieldDefinition::create('integer');
     $this->assertEquals(1, $definition->getCardinality());
     // @todo: Add more tests when this can be controlled.
   }
@@ -143,7 +143,7 @@ public function testFieldCardinality() {
    * Tests required.
    */
   public function testFieldRequired() {
-    $definition = new FieldDefinition();
+    $definition = FieldDefinition::create('integer');
     $this->assertFalse($definition->isRequired());
     $definition->setRequired(TRUE);
     $this->assertTrue($definition->isRequired());
@@ -155,7 +155,7 @@ public function testFieldRequired() {
    * Tests configurable.
    */
   public function testFieldConfigurable() {
-    $definition = new FieldDefinition();
+    $definition = FieldDefinition::create('integer');
     $this->assertFalse($definition->isConfigurable());
   }