diff --git a/core/lib/Drupal/Core/Entity/ContentEntityBase.php b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
index a8fc193..7d53cb9 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
@@ -10,6 +10,7 @@
 use Drupal\Core\Entity\Plugin\DataType\EntityReference;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\TypedData\DataDefinition;
 use Drupal\Core\TypedData\TypedDataInterface;
 
 /**
@@ -226,7 +227,7 @@ public function getDefinition() {
     else {
       $type = 'entity:' . $this->entityType();
     }
-    return array('type' => $type);
+    return DataDefinition::create($type);
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Entity/EntityManager.php b/core/lib/Drupal/Core/Entity/EntityManager.php
index 570ca21..ed359f6 100644
--- a/core/lib/Drupal/Core/Entity/EntityManager.php
+++ b/core/lib/Drupal/Core/Entity/EntityManager.php
@@ -353,13 +353,9 @@ public function getFieldDefinitions($entity_type, $bundle = NULL) {
         $result = $this->moduleHandler->invokeAll('entity_field_info', array($entity_type));
         $this->entityFieldInfo[$entity_type] = NestedArray::mergeDeep($this->entityFieldInfo[$entity_type], $result);
 
-        // Enforce field definitions to be objects.
+        // Automatically set the field name for non-configurable fields.
         foreach (array('definitions', 'optional') as $key) {
           foreach ($this->entityFieldInfo[$entity_type][$key] as $field_name => &$definition) {
-            if (is_array($definition)) {
-              $definition = FieldDefinition::createFromOldStyleDefinition($definition);
-            }
-            // Automatically set the field name for non-configurable fields.
             if ($definition instanceof FieldDefinition) {
               $definition->setFieldName($field_name);
             }
diff --git a/core/lib/Drupal/Core/Field/FieldItemBase.php b/core/lib/Drupal/Core/Field/FieldItemBase.php
index b1ea599..c329ed6 100644
--- a/core/lib/Drupal/Core/Field/FieldItemBase.php
+++ b/core/lib/Drupal/Core/Field/FieldItemBase.php
@@ -197,9 +197,9 @@ public function getConstraints() {
     $constraints = parent::getConstraints();
     // If property constraints are present add in a ComplexData constraint for
     // applying them.
-    if (!empty($this->definition['property_constraints'])) {
+    if ($property_constraints = $this->definition->getConstraints()) {
       $constraints[] = \Drupal::typedData()->getValidationConstraintManager()
-        ->create('ComplexData', $this->definition['property_constraints']);
+        ->create('ComplexData', $property_constraints);
     }
     return $constraints;
   }
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 23f9701..c1be221 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
@@ -8,6 +8,7 @@
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
 use Drupal\Core\Field\FieldItemBase;
+use Drupal\Core\TypedData\DataDefinition;
 
 /**
  * Defines the 'uri' entity field type.
@@ -34,13 +35,11 @@ class UriItem extends FieldItemBase {
    * Implements ComplexDataInterface::getPropertyDefinitions().
    */
   public function getPropertyDefinitions() {
-
     if (!isset(self::$propertyDefinitions)) {
-      self::$propertyDefinitions['value'] = array(
-        'type' => 'uri',
-        'label' => t('URI value'),
-      );
+      self::$propertyDefinitions['value'] = DataDefinition::create('uri')
+        ->setLabel(t('URI value'));
     }
     return self::$propertyDefinitions;
   }
+
 }
diff --git a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
index 3f90b5a..f3acbd3 100644
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
@@ -9,6 +9,7 @@
 
 use Drupal\Core\TypedData\Annotation\DataType;
 use Drupal\Core\Annotation\Translation;
+use Drupal\Core\TypedData\DataDefinition;
 use Drupal\Core\TypedData\TypedData;
 use Drupal\Core\TypedData\ComplexDataInterface;
 
@@ -49,9 +50,7 @@ class Map extends TypedData implements \IteratorAggregate, ComplexDataInterface
   public function getPropertyDefinitions() {
     $definitions = array();
     foreach ($this->values as $name => $value) {
-      $definitions[$name] = array(
-        'type' => 'any',
-      );
+      $definitions[$name] = DataDefinition::create('any');
     }
     return $definitions;
   }
@@ -150,7 +149,7 @@ public function set($property_name, $value, $notify = TRUE) {
   public function getProperties($include_computed = FALSE) {
     $properties = array();
     foreach ($this->getPropertyDefinitions() as $name => $definition) {
-      if ($include_computed || empty($definition['computed'])) {
+      if ($include_computed || !$definition->isComputed()) {
         $properties[$name] = $this->get($name);
       }
     }
diff --git a/core/lib/Drupal/Core/TypedData/TypedDataManager.php b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
index 27617fd..8205ea1 100644
--- a/core/lib/Drupal/Core/TypedData/TypedDataManager.php
+++ b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
@@ -188,9 +188,9 @@ public function getInstance(array $options) {
    */
   public function getPropertyInstance(TypedDataInterface $object, $property_name, $value = NULL) {
     $definition = $object->getRoot()->getDefinition();
-    $key = $definition['type'];
-    if (isset($definition['settings'])) {
-      $key .= ':' . implode(',', $definition['settings']);
+    $key = $definition->getDataType();
+    if ($settings = $definition->getSettings()) {
+      $key .= ':' . implode(',', $settings);
     }
     $key .= ':' . $object->getPropertyPath() . '.';
     // If we are creating list items, we always use 0 in the key as all list
diff --git a/core/modules/node/tests/modules/node_access_test/node_access_test.module b/core/modules/node/tests/modules/node_access_test/node_access_test.module
index 89ab1d0..12800b1 100644
--- a/core/modules/node/tests/modules/node_access_test/node_access_test.module
+++ b/core/modules/node/tests/modules/node_access_test/node_access_test.module
@@ -85,8 +85,7 @@ function node_access_test_entity_field_info($entity_type) {
   if ($entity_type === 'node') {
       $info['definitions']['private'] = FieldDefinition::create('boolean')
         ->setLabel(t('Private'))
-        ->setComputed(TRUE)
-        ->isList(TRUE);
+        ->setComputed(TRUE);
 
     return $info;
   }
diff --git a/core/modules/path/path.module b/core/modules/path/path.module
index 9cefaea..e638eb9 100644
--- a/core/modules/path/path.module
+++ b/core/modules/path/path.module
@@ -214,8 +214,7 @@ function path_entity_field_info($entity_type) {
   if ($entity_type === 'taxonomy_term' || $entity_type === 'node') {
     $info['definitions']['path'] = FieldDefinition::create('path')
       ->setLabel(t('The path alias'))
-      ->setComputed(TRUE)
-      ->isList(TRUE);
+      ->setComputed(TRUE);
 
     return $info;
   }
diff --git a/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php b/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
index 23f8b76..1408b47 100644
--- a/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php
@@ -53,7 +53,9 @@ public function setUp() {
    * @see \Drupal\Core\TypedData\TypedDataManager::create().
    */
   protected function createTypedData($definition, $value = NULL, $name = NULL) {
-    $definition = DataDefinition::create($definition['type']);
+    if (is_array($definition)) {
+      $definition = DataDefinition::create($definition['type']);
+    }
     $data = $this->typedData->create($definition, $value, $name);
     $this->assertTrue($data instanceof \Drupal\Core\TypedData\TypedDataInterface, 'Typed data object is an instance of the typed data interface.');
     return $data;
@@ -423,7 +425,7 @@ public function testTypedDataMaps() {
     // Test retrieving metadata.
     $this->assertEqual(array_keys($typed_data->getPropertyDefinitions()), array_keys($value));
     $definition = $typed_data->getPropertyDefinition('one');
-    $this->assertEqual($definition['type'], 'any');
+    $this->assertEqual($definition->getDataType(), 'any');
     $this->assertFalse($typed_data->getPropertyDefinition('invalid'));
 
     // Test getting and setting properties.
@@ -494,19 +496,17 @@ public function testTypedDataMaps() {
     $typed_data->set('zero', 'null');
     $this->assertEqual($typed_data->get('zero')->getValue(), 'null');
     $definition = $typed_data->getPropertyDefinition('zero');
-    $this->assertEqual($definition['type'], 'any', 'Definition for a new map entry returned.');
+    $this->assertEqual($definition->getDataType(), 'any', 'Definition for a new map entry returned.');
   }
 
   /**
    * Tests typed data validation.
    */
   public function testTypedDataValidation() {
-    $definition = array(
-      'type' => 'integer',
-      'constraints' => array(
+    $definition = DataDefinition::create('integer')
+      ->setConstraints(array(
         'Range' => array('min' => 5),
-      ),
-    );
+      ));
     $violations = $this->typedData->create($definition, 10)->validate();
     $this->assertEqual($violations->count(), 0);
 
@@ -521,25 +521,21 @@ public function testTypedDataValidation() {
     $this->assertIdentical($violations[0]->getRoot(), $integer, 'Root object returned.');
 
     // Test translating violation messages when pluralization is used.
-    $definition = array(
-      'type' => 'string',
-      'constraints' => array(
+    $definition = DataDefinition::create('string')
+      ->setConstraints(array(
         'Length' => array('min' => 10),
-      ),
-    );
+      ));
     $violations = $this->typedData->create($definition, "short")->validate();
     $this->assertEqual($violations->count(), 1);
     $message = t('This value is too short. It should have %limit characters or more.', array('%limit' => 10));
     $this->assertEqual($violations[0]->getMessage(), $message, 'Translated violation message retrieved.');
 
     // Test having multiple violations.
-    $definition = array(
-      'type' => 'integer',
-      'constraints' => array(
+    $definition = DataDefinition::create('integer')
+      ->setConstraints(array(
         'Range' => array('min' => 5),
         'Null' => array(),
-      ),
-    );
+      ));
     $violations = $this->typedData->create($definition, 10)->validate();
     $this->assertEqual($violations->count(), 1);
     $violations = $this->typedData->create($definition, 1)->validate();
@@ -585,10 +581,8 @@ public function testTypedDataValidation() {
     $this->assertTrue(isset($definitions['NotNull']), 'Constraint plugin found for type string.');
 
     // Test automatic 'required' validation.
-    $definition = array(
-      'type' => 'integer',
-      'required' => TRUE,
-    );
+    $definition = DataDefinition::create('integer')
+      ->setRequired(TRUE);
     $violations = $this->typedData->create($definition)->validate();
     $this->assertEqual($violations->count(), 1);
     $violations = $this->typedData->create($definition, 0)->validate();
@@ -596,8 +590,7 @@ public function testTypedDataValidation() {
 
     // Test validating a list of a values and make sure property paths starting
     // with "0" are created.
-    $definition = FieldDefinition::create('integer')
-      ->isList(TRUE);
+    $definition = FieldDefinition::create('integer');
     $violations = $this->typedData->create($definition, array(array('value' => 10)))->validate();
     $this->assertEqual($violations->count(), 0);
     $violations = $this->typedData->create($definition, array(array('value' => 'string')))->validate();
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 0d3c138..08525d1 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\TypedData\DataDefinition;
 use Drupal\field\FieldInterface;
 
 /**
@@ -40,20 +41,17 @@ public function getPropertyDefinitions() {
     if (!isset(static::$propertyDefinitions)) {
       static::$propertyDefinitions = parent::getPropertyDefinitions();
 
-      static::$propertyDefinitions['summary'] = array(
-        'type' => 'string',
-        'label' => t('Summary text value'),
-      );
-      static::$propertyDefinitions['summary_processed'] = array(
-        'type' => 'string',
-        'label' => t('Processed summary text'),
-        'description' => t('The summary text value with the text format applied.'),
-        'computed' => TRUE,
-        'class' => '\Drupal\text\TextProcessed',
-        'settings' => array(
+      static::$propertyDefinitions['summary'] = DataDefinition::create('string')
+        ->setLabel(t('Summary text value'));
+
+      static::$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')
+        ->setSettings(array(
           'text source' => 'summary',
-        ),
-      );
+        ));
     }
     return static::$propertyDefinitions;
   }