core/modules/media/src/Entity/Media.php            |  6 +--
 core/modules/media/src/MediaStorageProxyBase.php   |  2 +-
 .../media/src/MediaStorageProxyInterface.php       | 25 ---------
 .../MediaStorageProxyMetadataHandlerInterface.php  | 63 ++++++++++++++++++++++
 core/modules/media/src/MediaTypeForm.php           | 10 ++--
 .../src/Plugin/MediaStorageProxy/Test.php          | 12 ++---
 .../FunctionalJavascript/MediaUiJavascriptTest.php | 12 ++---
 7 files changed, 82 insertions(+), 48 deletions(-)

diff --git a/core/modules/media/src/Entity/Media.php b/core/modules/media/src/Entity/Media.php
index dbf79d0..12b6900 100644
--- a/core/modules/media/src/Entity/Media.php
+++ b/core/modules/media/src/Entity/Media.php
@@ -139,11 +139,11 @@ public function preSave(EntityStorageInterface $storage) {
 
     // Try to set fields provided by the media handler and mapped in
     // media type config.
-    foreach ($this->bundle->entity->getFieldMap() as $source_field => $destination_field) {
+    foreach ($this->bundle->entity->getFieldMap() as $metadata_attribute_name => $entity_field_name) {
       // Only save value in entity field if empty. Do not overwrite existing
       // data.
-      if ($this->hasField($destination_field) && $this->get($destination_field)->isEmpty() && ($value = $this->getHandler()->getField($this, $source_field))) {
-        $this->set($destination_field, $value);
+      if ($this->hasField($entity_field_name) && $this->get($entity_field_name)->isEmpty() && ($value = $this->getHandler()->getMetadata($this, $metadata_attribute_name))) {
+        $this->set($entity_field_name, $value);
       }
     }
 
diff --git a/core/modules/media/src/MediaStorageProxyBase.php b/core/modules/media/src/MediaStorageProxyBase.php
index 1b92e8f..b3a277b 100644
--- a/core/modules/media/src/MediaStorageProxyBase.php
+++ b/core/modules/media/src/MediaStorageProxyBase.php
@@ -15,7 +15,7 @@
 /**
  * Base implementation of media storage proxy plugin.
  */
-abstract class MediaStorageProxyBase extends PluginBase implements SourceFieldInterface, ContainerFactoryPluginInterface {
+abstract class MediaStorageProxyBase extends PluginBase implements SourceFieldInterface, MediaStorageProxyMetadataHandlerInterface, ContainerFactoryPluginInterface {
 
   /**
    * Plugin label.
diff --git a/core/modules/media/src/MediaStorageProxyInterface.php b/core/modules/media/src/MediaStorageProxyInterface.php
index 3685cba..88d44c0 100644
--- a/core/modules/media/src/MediaStorageProxyInterface.php
+++ b/core/modules/media/src/MediaStorageProxyInterface.php
@@ -62,31 +62,6 @@
 interface MediaStorageProxyInterface extends PluginInspectionInterface, ConfigurablePluginInterface, PluginFormInterface {
 
   /**
-   * Gets list of fields provided by this plugin.
-   *
-   * @return array
-   *   Associative array with field names as keys and arrays as values. Each
-   *   of those arrays should have the following values:
-   *   - label: human-readable label of the field
-   *   - field_type: (optional) entity field type that the field should be
-   *     mapped to by default. "string" will be assumed if omitted.
-   */
-  public function getProvidedFields();
-
-  /**
-   * Gets a media-related field/value.
-   *
-   * @param \Drupal\media\MediaInterface $media
-   *   A media item.
-   * @param string $name
-   *   Name of field to fetch.
-   *
-   * @return mixed|false
-   *   Field value or FALSE if data unavailable.
-   */
-  public function getField(MediaInterface $media, $name);
-
-  /**
    * Attaches media handler-specific validation constraints to a media item.
    *
    * @param \Drupal\media\MediaInterface $media
diff --git a/core/modules/media/src/MediaStorageProxyMetadataHandlerInterface.php b/core/modules/media/src/MediaStorageProxyMetadataHandlerInterface.php
new file mode 100644
index 0000000..0ab5745
--- /dev/null
+++ b/core/modules/media/src/MediaStorageProxyMetadataHandlerInterface.php
@@ -0,0 +1,63 @@
+<?php
+
+namespace Drupal\media;
+
+use Drupal\Component\Plugin\ConfigurablePluginInterface;
+use Drupal\Component\Plugin\PluginInspectionInterface;
+use Drupal\Core\Plugin\PluginFormInterface;
+
+/**
+ * Defines an interface for media storage proxy metadata handlers.
+ *
+ * A media storage proxy brings (proxies) media regardless of storage into
+ * Drupal. But merely exposing the media itself is often not enough, most media
+ * have associated metadata, describing attributes such as:
+ * - dimensions
+ * - duration
+ * - encoding
+ * - date
+ * - location
+ * - permalink
+ * - licensing information
+ * - …
+ *
+ * A metadata handler for a media storage proxy allows Drupal to operate on the
+ * metadata for each media item pulled into Drupal via a media storage proxy.
+ *
+ * This interface exposes all metadata attributes that a media storage proxy MAY
+ * offer. In other words: it is possible that a particular media item does not
+ * contain a certain attribute. For example: an oEmbed media storage proxy can
+ * proxy both video and images. Images don't have a duration, but videos do.
+ *
+ * (The term 'attributes' was chosen because it cannot be confused with 'fields'
+ * and 'properties', both of which are concepts in Drupal's Entity Field API.)
+ *
+ * @see \Drupal\media\MediaStorageProxyInterface
+ */
+interface MediaStorageProxyMetadataHandlerInterface extends MediaStorageProxyInterface {
+
+  /**
+   * Gets labels for metadata attributes.
+   *
+   * @return array
+   *   Associative array with:
+   *   - keys: metadata attribute names
+   *   - values: human-readable labels for those attribute names
+   *   Must list every possible metadata attribute, including optional ones.
+   */
+  public function getMetadataLabels();
+
+  /**
+   * Gets the value for a metadata attribute for a given media item.
+   *
+   * @param \Drupal\media\MediaInterface $media
+   *   A media item.
+   * @param string $attribute_name
+   *   Name of attribute to fetch.
+   *
+   * @return mixed|false
+   *   Metadata attribute value or FALSE if unavailable.
+   */
+  public function getMetadata(MediaInterface $media, $attribute_name);
+
+}
diff --git a/core/modules/media/src/MediaTypeForm.php b/core/modules/media/src/MediaTypeForm.php
index 11c019a..2b774a6 100644
--- a/core/modules/media/src/MediaTypeForm.php
+++ b/core/modules/media/src/MediaTypeForm.php
@@ -151,7 +151,7 @@ public function form(array $form, FormStateInterface $form_state) {
       ],
     ];
 
-    if (empty($handler) || empty($handler->getProvidedFields())) {
+    if (empty($handler) || empty($handler->getMetadataLabels())) {
       $form['handler_dependent']['field_map']['#access'] = FALSE;
     }
     else {
@@ -163,12 +163,12 @@ public function form(array $form, FormStateInterface $form_state) {
       }
 
       $field_map = $this->entity->getFieldMap();
-      foreach ($handler->getProvidedFields() as $field_name => $field_definition) {
-        $form['handler_dependent']['field_map'][$field_name] = [
+      foreach ($handler->getMetadataLabels() as $metadata_attribute_name => $metadata_attribute_label) {
+        $form['handler_dependent']['field_map'][$metadata_attribute_name] = [
           '#type' => 'select',
-          '#title' => $field_definition['label'],
+          '#title' => $metadata_attribute_label,
           '#options' => $options,
-          '#default_value' => isset($field_map[$field_name]) ? $field_map[$field_name] : '_none',
+          '#default_value' => isset($field_map[$metadata_attribute_name]) ? $field_map[$metadata_attribute_name] : '_none',
         ];
       }
     }
diff --git a/core/modules/media/tests/modules/media_test_handler/src/Plugin/MediaStorageProxy/Test.php b/core/modules/media/tests/modules/media_test_handler/src/Plugin/MediaStorageProxy/Test.php
index 5756a3b..b70bf2c 100644
--- a/core/modules/media/tests/modules/media_test_handler/src/Plugin/MediaStorageProxy/Test.php
+++ b/core/modules/media/tests/modules/media_test_handler/src/Plugin/MediaStorageProxy/Test.php
@@ -28,21 +28,17 @@ public function getThumbnail(MediaInterface $media) {
   /**
    * {@inheritdoc}
    */
-  public function getProvidedFields() {
+  public function getMetadataLabels() {
     return [
-      'field_1' => [
-        'label' => $this->t('Field 1'),
-      ],
-      'field_2' => [
-        'label' => $this->t('Field 2'),
-      ],
+      'attribute_1' => $this->t('Attribute 1'),
+      'attribute_2' => $this->t('Attribute 2'),
     ];
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getField(MediaInterface $media, $name) {
+  public function getMetadata(MediaInterface $media, $attribute_name) {
     return FALSE;
   }
 
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
index a153d50..a2bcb23 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
@@ -99,8 +99,8 @@ public function testMediaTypes() {
     $assert_session->assertWaitOnAjaxRequest();
     $assert_session->fieldExists('Test config value');
     $assert_session->fieldValueEquals('Test config value', 'This is default value.');
-    $assert_session->fieldExists('Field 1');
-    $assert_session->fieldExists('Field 2');
+    $assert_session->fieldExists('Attribute 1');
+    $assert_session->fieldExists('Attribute 2');
 
     // Test if the edit machine name is not editable.
     $assert_session->fieldDisabled('Machine-readable name');
@@ -112,7 +112,7 @@ public function testMediaTypes() {
     $page->fillField('description', $new_description);
     $page->selectFieldOption('handler', 'test');
     $page->fillField('Test config value', 'This is new config value.');
-    $page->selectFieldOption('field_map[field_1]', 'name');
+    $page->selectFieldOption('field_map[attribute_1]', 'name');
     $page->checkField('options[new_revision]');
     $page->uncheckField('options[status]');
     $page->checkField('options[queue_thumbnail_downloads]');
@@ -128,8 +128,8 @@ public function testMediaTypes() {
     $assert_session->checkboxNotChecked('options[status]');
     $assert_session->checkboxChecked('options[queue_thumbnail_downloads]');
     $assert_session->fieldValueEquals('Test config value', 'This is new config value.');
-    $assert_session->fieldValueEquals('Field 1', 'name');
-    $assert_session->fieldValueEquals('Field 2', '_none');
+    $assert_session->fieldValueEquals('Attribute 1', 'name');
+    $assert_session->fieldValueEquals('Attribute 2', '_none');
 
     /** @var \Drupal\media\MediaTypeInterface $loaded_media_type */
     $loaded_media_type = $this->container->get('entity_type.manager')
@@ -143,7 +143,7 @@ public function testMediaTypes() {
     $this->assertTrue($loaded_media_type->shouldCreateNewRevision());
     $this->assertTrue($loaded_media_type->thumbnailDownloadsAreQueued());
     $this->assertFalse($loaded_media_type->getStatus());
-    $this->assertEquals($loaded_media_type->getFieldMap(), ['field_1' => 'name']);
+    $this->assertEquals($loaded_media_type->getFieldMap(), ['attribute_1' => 'name']);
 
     // We need to clear the statically cached field definitions to account for
     // fields that have been created by API calls in this test, since they exist