diff --git a/core/modules/migrate/src/Annotation/MigrateDestination.php b/core/modules/migrate/src/Annotation/MigrateDestination.php
index 1fd51d7..69b2ce6 100644
--- a/core/modules/migrate/src/Annotation/MigrateDestination.php
+++ b/core/modules/migrate/src/Annotation/MigrateDestination.php
@@ -7,10 +7,10 @@
 /**
  * Defines a migration destination plugin annotation object.
  *
- * Plugin Namespace: Plugin\migrate\destination
+ * Plugin Namespace: Plugin\migrate\destination.
  *
  * For a working example, see
- * \Drupal\migrate\Plugin\migrate\destination\UrlAlias
+ * \Drupal\migrate\Plugin\migrate\destination\UrlAlias.
  *
  * @see \Drupal\migrate\Plugin\MigrateDestinationInterface
  * @see \Drupal\migrate\Plugin\destination\DestinationBase
diff --git a/core/modules/migrate/src/Annotation/MigrateProcessPlugin.php b/core/modules/migrate/src/Annotation/MigrateProcessPlugin.php
index f08da3b..d731ebb 100644
--- a/core/modules/migrate/src/Annotation/MigrateProcessPlugin.php
+++ b/core/modules/migrate/src/Annotation/MigrateProcessPlugin.php
@@ -7,7 +7,7 @@
 /**
  * Defines a migration process plugin annotation object.
  *
- * Plugin Namespace: Plugin\migrate\process
+ * Plugin Namespace: Plugin\migrate\process.
  *
  * For a working example, see
  * \Drupal\migrate\Plugin\migrate\process\DefaultValue
diff --git a/core/modules/migrate/src/Annotation/MigrateSource.php b/core/modules/migrate/src/Annotation/MigrateSource.php
index a73f7a5..8401810 100644
--- a/core/modules/migrate/src/Annotation/MigrateSource.php
+++ b/core/modules/migrate/src/Annotation/MigrateSource.php
@@ -7,7 +7,7 @@
 /**
  * Defines a migration source plugin annotation object.
  *
- * Plugin Namespace: Plugin\migrate\source
+ * Plugin Namespace: Plugin\migrate\source.
  *
  * For a working example, check
  * \Drupal\migrate\Plugin\migrate\source\EmptySource
diff --git a/core/modules/migrate/src/Event/MigrateEvents.php b/core/modules/migrate/src/Event/MigrateEvents.php
index edc2bec..6f2c484 100644
--- a/core/modules/migrate/src/Event/MigrateEvents.php
+++ b/core/modules/migrate/src/Event/MigrateEvents.php
@@ -36,7 +36,8 @@
    *
    * This event allows modules to perform an action whenever a row is deleted
    * from a migration's map table (implying it has been rolled back). The event
-   * listener method receives a \Drupal\migrate\Event\MigrateMapDeleteEvent instance.
+   * listener method receives a \Drupal\migrate\Event\MigrateMapDeleteEvent
+   * instance.
    *
    * @Event
    *
diff --git a/core/modules/migrate/src/Event/MigrateIdMapMessageEvent.php b/core/modules/migrate/src/Event/MigrateIdMapMessageEvent.php
index 2bf774f..26f886d 100644
--- a/core/modules/migrate/src/Event/MigrateIdMapMessageEvent.php
+++ b/core/modules/migrate/src/Event/MigrateIdMapMessageEvent.php
@@ -46,7 +46,7 @@ class MigrateIdMapMessageEvent extends Event {
    * @param array $source_id_values
    *   Values represent the source ID.
    * @param string $message
-   *   The message
+   *   The message to be logged.
    * @param int $level
    *   Severity level (one of the MigrationInterface::MESSAGE_* constants).
    */
@@ -88,8 +88,9 @@ public function getMessage() {
   }
 
   /**
-   * Gets the severity level of the message (one of the
-   * MigrationInterface::MESSAGE_* constants).
+   * Gets the severity level of the message.
+   *
+   * This will be one of the MigrationInterface::MESSAGE_* constants.
    *
    * @return int
    *   The message level.
diff --git a/core/modules/migrate/src/Event/MigrateMapDeleteEvent.php b/core/modules/migrate/src/Event/MigrateMapDeleteEvent.php
index 331331c..2b04eb0 100644
--- a/core/modules/migrate/src/Event/MigrateMapDeleteEvent.php
+++ b/core/modules/migrate/src/Event/MigrateMapDeleteEvent.php
@@ -30,7 +30,8 @@ class MigrateMapDeleteEvent extends Event {
    * @param \Drupal\migrate\Plugin\MigrateIdMapInterface $map
    *   Map plugin.
    * @param array $source_id
-   *   Array of source ID fields representing the object being deleted from the map.
+   *   Array of source ID fields representing the object being deleted from the
+   *   map.
    */
   public function __construct(MigrateIdMapInterface $map, array $source_id) {
     $this->map = $map;
diff --git a/core/modules/migrate/src/Exception/RequirementsException.php b/core/modules/migrate/src/Exception/RequirementsException.php
index 4c17dd6..bb5b3c6 100644
--- a/core/modules/migrate/src/Exception/RequirementsException.php
+++ b/core/modules/migrate/src/Exception/RequirementsException.php
@@ -5,7 +5,7 @@
 use Exception;
 
 /**
- * Defines an
+ * Defines a requirements exception.
  *
  * @see \Drupal\migrate\Plugin\RequirementsInterface
  */
@@ -22,13 +22,14 @@ class RequirementsException extends \RuntimeException {
    * Constructs a new RequirementsException instance.
    *
    * @param string $message
-   *   (optional) The Exception message to throw.
+   *   (optional) The Exception message to throw. Defaults to an empty string.
    * @param array $requirements
-   *   (optional) The missing requirements.
+   *   (optional) The missing requirements. Defaults to an empty array.
    * @param int $code
-   *   (optional) The Exception code.
+   *   (optional) The Exception code. Defaults to zero.
    * @param \Exception $previous
    *   (optional) The previous exception used for the exception chaining.
+   *   Defaults to NULL.
    */
   public function __construct($message = "", array $requirements = [], $code = 0, Exception $previous = NULL) {
     parent::__construct($message, $code, $previous);
@@ -37,7 +38,7 @@ public function __construct($message = "", array $requirements = [], $code = 0,
   }
 
   /**
-   * Get an array of requirements.
+   * Gets an array of requirements.
    *
    * @return array
    *   The requirements.
@@ -47,7 +48,7 @@ public function getRequirements() {
   }
 
   /**
-   * Get the requirements as a string.
+   * Gets the requirements as a string.
    *
    * @return string
    *   A formatted requirements string.
diff --git a/core/modules/migrate/src/MigrateBuildDependencyInterface.php b/core/modules/migrate/src/MigrateBuildDependencyInterface.php
index bb02c88..6545c2c 100644
--- a/core/modules/migrate/src/MigrateBuildDependencyInterface.php
+++ b/core/modules/migrate/src/MigrateBuildDependencyInterface.php
@@ -1,12 +1,19 @@
 <?php
 
-namespace Drupal\migrate;
+/**
+ * @file
+ * Contains \Drupal\migrate\MigrateBuildDependencyInterface.
+ */
 
+namespace Drupal\migrate;
 
+/**
+ * Defines the interface for building a migration dependency tree.
+ */
 interface MigrateBuildDependencyInterface {
 
   /**
-   * Builds a dependency tree for the migrations and set their order.
+   * Builds a dependency tree for the migrations and sets their order.
    *
    * @param \Drupal\migrate\Plugin\MigrationInterface[] $migrations
    *   Array of loaded migrations with their declared dependencies.
diff --git a/core/modules/migrate/src/MigrateException.php b/core/modules/migrate/src/MigrateException.php
index 8047bb3..e43c382 100644
--- a/core/modules/migrate/src/MigrateException.php
+++ b/core/modules/migrate/src/MigrateException.php
@@ -31,17 +31,20 @@ class MigrateException extends \Exception {
   /**
    * Constructs a MigrateException object.
    *
-   * @param string $message
-   *   The message for the exception.
+   * @param string|null $message
+   *   (optional) The message for the exception. Defaults to NULL.
    * @param int $code
-   *   The Exception code.
-   * @param \Exception $previous
-   *   The previous exception used for the exception chaining.
+   *   (optional) The Exception code. Defaults to zero.
+   * @param \Exception|null $previous
+   *   (optional) The previous exception used for the exception chaining.
+   *   Defaults to NULL.
    * @param int $level
-   *   The level of the error, a Migration::MESSAGE_* constant.
+   *   (optional) The level of the error, a Migration::MESSAGE_* constant.
+   *   Defaults to MigrationInterface::MESSAGE_ERROR.
    * @param int $status
-   *   The status of the item for the map table, a MigrateMap::STATUS_*
-   *   constant.
+   *   (optional) The status of the item for the map table, a
+   *   MigrateMap::STATUS_* constant. Defaults to
+   *   MigrateIdMapInterface::STATUS_FAILED.
    */
   public function __construct($message = NULL, $code = 0, \Exception $previous = NULL, $level = MigrationInterface::MESSAGE_ERROR, $status = MigrateIdMapInterface::STATUS_FAILED) {
     $this->level = $level;
@@ -53,7 +56,9 @@ public function __construct($message = NULL, $code = 0, \Exception $previous = N
    * Gets the level.
    *
    * @return int
-   *   An integer status code. @see Migration::MESSAGE_*
+   *   An integer status code.
+   *
+   * @see Migration::MESSAGE_*
    */
   public function getLevel() {
     return $this->level;
@@ -63,7 +68,9 @@ public function getLevel() {
    * Gets the status of the current item.
    *
    * @return int
-   *   An integer status code. @see MigrateMap::STATUS_*
+   *   An integer status code.
+   *
+   * @see MigrateMap::STATUS_*
    */
   public function getStatus() {
     return $this->status;
diff --git a/core/modules/migrate/src/MigrateExecutable.php b/core/modules/migrate/src/MigrateExecutable.php
index c0b3537..fc2e4e4 100644
--- a/core/modules/migrate/src/MigrateExecutable.php
+++ b/core/modules/migrate/src/MigrateExecutable.php
@@ -101,8 +101,8 @@ class MigrateExecutable implements MigrateExecutableInterface {
    *   The migration to run.
    * @param \Drupal\migrate\MigrateMessageInterface $message
    *   The message to record.
-   * @param \Symfony\Component\EventDispatcher\EventDispatcherInterface $event_dispatcher
-   *   The event dispatcher.
+   * @param \Symfony\Component\EventDispatcher\EventDispatcherInterface|null $event_dispatcher
+   *   The event dispatcher. Defaults to NULL.
    *
    * @throws \Drupal\migrate\MigrateException
    */
@@ -111,7 +111,7 @@ public function __construct(MigrationInterface $migration, MigrateMessageInterfa
     $this->message = $message;
     $this->migration->getIdMap()->setMessage($message);
     $this->eventDispatcher = $event_dispatcher;
-    // Record the memory limit in bytes
+    // Record the memory limit in bytes.
     $limit = trim(ini_get('memory_limit'));
     if ($limit == '-1') {
       $this->memoryLimit = PHP_INT_MAX;
@@ -127,6 +127,7 @@ public function __construct(MigrationInterface $migration, MigrateMessageInterfa
           case 'k':
             $limit *= 1024;
             break;
+
           default:
             $limit = PHP_INT_MAX;
             $this->message->display($this->t('Invalid PHP memory_limit @limit, setting to unlimited.',
@@ -156,6 +157,7 @@ protected function getSource() {
    * Gets the event dispatcher.
    *
    * @return \Symfony\Component\EventDispatcher\EventDispatcherInterface
+   *   The event dispatcher service.
    */
   protected function getEventDispatcher() {
     if (!$this->eventDispatcher) {
@@ -306,8 +308,8 @@ public function rollback() {
     // Announce that rollback is about to happen.
     $this->getEventDispatcher()->dispatch(MigrateEvents::PRE_ROLLBACK, new MigrateRollbackEvent($this->migration));
 
-    // Optimistically assume things are going to work out; if not, $return will be
-    // updated to some other status.
+    // Optimistically assume things are going to work out; if not, $return will
+    // be updated to some other status.
     $return = MigrationInterface::RESULT_COMPLETED;
 
     $this->migration->setStatus(MigrationInterface::STATUS_ROLLING_BACK);
@@ -433,7 +435,8 @@ public function saveMessage($message, $level = MigrationInterface::MESSAGE_ERROR
    *   Object representing the exception.
    * @param bool $save
    *   (optional) Whether to save the message in the migration's mapping table.
-   *   Set to FALSE in contexts where this doesn't make sense.
+   *   Set to FALSE in contexts where this does not make sense. Defaults to
+   *   TRUE.
    */
   protected function handleException(\Exception $exception, $save = TRUE) {
     $result = Error::decodeException($exception);
@@ -455,7 +458,7 @@ protected function checkStatus() {
   }
 
   /**
-   * Tests whether we've exceeded the desired memory threshold.
+   * Tests whether we have exceeded the desired memory threshold.
    *
    * If so, output a message.
    *
@@ -477,8 +480,8 @@ protected function memoryExceeded() {
         'warning');
       $usage = $this->attemptMemoryReclaim();
       $pct_memory = $usage / $this->memoryLimit;
-      // Use a lower threshold - we don't want to be in a situation where we keep
-      // coming back here and trimming a tiny amount
+      // Use a lower threshold - we do not want to be in a situation where we
+      // keep coming back here and trimming a tiny amount.
       if ($pct_memory > (0.90 * $threshold)) {
         $this->message->display(
           $this->t('Memory usage is now @usage (@pct% of limit @limit), not enough reclaimed, starting new batch',
@@ -530,7 +533,8 @@ protected function attemptMemoryReclaim() {
       $manager->getStorage($id)->resetCache();
     }
 
-    // @TODO: explore resetting the container.
+    // @todo Explore resetting the container.  This should be addressed in issue
+    //   https://www.drupal.org/node/2545632.
 
     return memory_get_usage();
   }
diff --git a/core/modules/migrate/src/MigrateExecutableInterface.php b/core/modules/migrate/src/MigrateExecutableInterface.php
index 33d5914..57bd553 100644
--- a/core/modules/migrate/src/MigrateExecutableInterface.php
+++ b/core/modules/migrate/src/MigrateExecutableInterface.php
@@ -4,6 +4,9 @@
 
 use Drupal\migrate\Plugin\MigrationInterface;
 
+/**
+ * Defines an interface for a migration executable class.
+ */
 interface MigrateExecutableInterface {
 
   /**
@@ -23,14 +26,14 @@ public function rollback();
    *   The $row to be processed.
    * @param array $process
    *   (optional) A process pipeline configuration. If not set, the top level
-   *   process configuration in the migration entity is used.
+   *   process configuration in the migration entity is used. Defaults to NULL.
    * @param mixed $value
    *   (optional) Initial value of the pipeline for the first destination.
    *   Usually setting this is not necessary as $process typically starts with
    *   a 'get'. This is useful only when the $process contains a single
    *   destination and needs to access a value outside of the source. See
    *   \Drupal\migrate\Plugin\migrate\process\Iterator::transformKey for an
-   *   example.
+   *   example. Defaults to NULL.
    *
    * @throws \Drupal\migrate\MigrateException
    */
@@ -42,7 +45,8 @@ public function processRow(Row $row, array $process = NULL, $value = NULL);
    * @param string $message
    *   The message to record.
    * @param int $level
-   *   (optional) Message severity (defaults to MESSAGE_ERROR).
+   *   (optional) Message severity. Defaults to
+   *   MigrationInterface::MESSAGE_ERROR.
    */
   public function saveMessage($message, $level = MigrationInterface::MESSAGE_ERROR);
 
diff --git a/core/modules/migrate/src/MigrateMessageInterface.php b/core/modules/migrate/src/MigrateMessageInterface.php
index 628a684..4069547 100644
--- a/core/modules/migrate/src/MigrateMessageInterface.php
+++ b/core/modules/migrate/src/MigrateMessageInterface.php
@@ -1,8 +1,15 @@
 <?php
 
-namespace Drupal\migrate;
+/**
+ * @file
+ * Contains \Drupal\migrate\MigrateMessageInterface.
+ */
 
+namespace Drupal\migrate;
 
+/**
+ * Defines the interface for a migration message class.
+ */
 interface MigrateMessageInterface {
 
   /**
@@ -11,7 +18,8 @@
    * @param string $message
    *   The message to display.
    * @param string $type
-   *   The type of message, for example: status or warning.
+   *   (optional) The type of message, for example: status or warning. Defaults
+   *   to 'status'.
    */
   public function display($message, $type = 'status');
 
diff --git a/core/modules/migrate/src/MigrateTemplateStorage.php b/core/modules/migrate/src/MigrateTemplateStorage.php
new file mode 100644
index 0000000..a4d305f
--- /dev/null
+++ b/core/modules/migrate/src/MigrateTemplateStorage.php
@@ -0,0 +1,89 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\migrate\MigrateTemplateStorage.
+ */
+
+namespace Drupal\migrate;
+
+use Drupal\Component\Serialization\Yaml;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+
+/**
+ * Storage to access migration template configuration in enabled extensions.
+ */
+class MigrateTemplateStorage implements MigrateTemplateStorageInterface {
+
+  /**
+   * Extension sub-directory containing default configuration for migrations.
+   */
+  const MIGRATION_TEMPLATE_DIRECTORY = 'migration_templates';
+
+  /**
+   * Template subdirectory.
+   *
+   * @var string
+   */
+  protected $directory;
+
+  /**
+   * The module handler service.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct(ModuleHandlerInterface $module_handler, $directory = self::MIGRATION_TEMPLATE_DIRECTORY) {
+    $this->moduleHandler = $module_handler;
+    $this->directory = $directory;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function findTemplatesByTag($tag) {
+    $templates = $this->getAllTemplates();
+    $matched_templates = [];
+    foreach ($templates as $template_name => $template) {
+      if (!empty($template['migration_tags'])) {
+        if (in_array($tag, $template['migration_tags'])) {
+          $matched_templates[$template_name] = $template;
+        }
+      }
+    }
+    return $matched_templates;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTemplateByName($name) {
+    $templates = $this->getAllTemplates();
+    return isset($templates[$name]) ? $templates[$name] : NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getAllTemplates() {
+    $templates = [];
+    foreach ($this->moduleHandler->getModuleDirectories() as $directory) {
+      $full_directory = $directory . '/' . $this->directory;
+      if (file_exists($full_directory)) {
+        $files = scandir($full_directory);
+        foreach ($files as $file) {
+          if ($file[0] !== '.' && fnmatch('*.yml', $file)) {
+            $templates[basename($file, '.yml')] = Yaml::decode(file_get_contents("$full_directory/$file"));
+          }
+        }
+      }
+    }
+
+    return $templates;
+  }
+
+}
diff --git a/core/modules/migrate/src/MigrateTemplateStorageInterface.php b/core/modules/migrate/src/MigrateTemplateStorageInterface.php
new file mode 100644
index 0000000..4e8f1b8
--- /dev/null
+++ b/core/modules/migrate/src/MigrateTemplateStorageInterface.php
@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\migrate\MigrateTemplateStorageInterface.
+ */
+
+namespace Drupal\migrate;
+
+/**
+ * The MigrateTemplateStorageInterface interface.
+ */
+interface MigrateTemplateStorageInterface {
+
+  /**
+   * Find all migration templates with the specified tag.
+   *
+   * @param $tag
+   *   The tag to match.
+   *
+   * @return array
+   *   Any templates (parsed YAML config) that matched, keyed by the ID.
+   */
+  public function findTemplatesByTag($tag);
+
+  /**
+   * Retrieve a template given a specific name.
+   *
+   * @param string $name
+   *   A migration template name.
+   *
+   * @return array|null
+   *   A parsed migration template, or NULL if it does not exist.
+   */
+  public function getTemplateByName($name);
+
+  /**
+   * Retrieves all migration templates belonging to enabled extensions.
+   *
+   * @return array
+   *   Array of parsed templates, keyed by the fully-qualified id.
+   */
+  public function getAllTemplates();
+
+}
diff --git a/core/modules/migrate/src/Plugin/Migration.php b/core/modules/migrate/src/Plugin/Migration.php
index 86294b5..3658585 100644
--- a/core/modules/migrate/src/Plugin/Migration.php
+++ b/core/modules/migrate/src/Plugin/Migration.php
@@ -135,7 +135,9 @@ class Migration extends PluginBase implements MigrationInterface, RequirementsIn
   protected $highWaterProperty;
 
   /**
-   * Indicate whether the primary system of record for this migration is the
+   * Specifies the primary system of record for this migration.
+   *
+   * Indicates whether the primary system of record for this migration is the
    * source, or the destination (Drupal). In the source case, migration of
    * an existing object will completely replace the Drupal object with data from
    * the source side. In the destination case, the existing Drupal object will
@@ -147,14 +149,17 @@ class Migration extends PluginBase implements MigrationInterface, RequirementsIn
   protected $systemOfRecord = self::SOURCE;
 
   /**
-   * Specify value of source_row_status for current map row. Usually set by
-   * MigrateFieldHandler implementations.
+   * Specifies the value of source_row_status for current map row.
+   *
+   * Usually this is set by MigrateFieldHandler implementations.
    *
    * @var int
    */
   protected $sourceRowStatus = MigrateIdMapInterface::STATUS_IMPORTED;
 
   /**
+   * The highwater value for this migration.
+   *
    * @var \Drupal\Core\KeyValueStore\KeyValueStoreInterface
    */
   protected $highWaterStorage;
@@ -386,7 +391,7 @@ public function getProcessPlugins(array $process = NULL) {
   }
 
   /**
-   * Resolve shorthands into a list of plugin configurations.
+   * Resolves shorthands into a list of plugin configurations.
    *
    * @param array $process
    *   A process configuration array.
@@ -437,7 +442,7 @@ public function getIdMap() {
   }
 
   /**
-   * Get the high water storage object.
+   * Gets the high water storage object.
    *
    * @return \Drupal\Core\KeyValueStore\KeyValueStoreInterface
    *   The storage object.
@@ -616,7 +621,7 @@ public function setProcessOfProperty($property, $process_of_property) {
    */
   public function mergeProcessOfProperty($property, array $process_of_property) {
     // If we already have a process value then merge the incoming process array
-    //otherwise simply set it.
+    // otherwise simply set it.
     $current_process = $this->getProcess();
     if (isset($current_process[$property])) {
       $this->process = NestedArray::mergeDeepArray([$current_process, $this->getProcessNormalized([$property => $process_of_property])], TRUE);
diff --git a/core/modules/migrate/src/Plugin/MigrationInterface.php b/core/modules/migrate/src/Plugin/MigrationInterface.php
index 7572760..f6a3aaf 100644
--- a/core/modules/migrate/src/Plugin/MigrationInterface.php
+++ b/core/modules/migrate/src/Plugin/MigrationInterface.php
@@ -124,8 +124,8 @@ public function getSourcePlugin();
   /**
    * Returns the process plugins.
    *
-   * @param array $process
-   *   A process configuration array.
+   * @param array|null $process
+   *   (optional) A process configuration array. Defaults to NULL.
    *
    * @return \Drupal\migrate\Plugin\MigrateProcessInterface[][]
    *   An associative array. The keys are the destination property names. Values
@@ -137,7 +137,8 @@ public function getProcessPlugins(array $process = NULL);
    * Returns the initialized destination plugin.
    *
    * @param bool $stub_being_requested
-   *   TRUE to indicate that this destination will be asked to construct a stub.
+   *   (optional) TRUE to indicate that this destination will be asked to
+   *   construct a stub. Defaults to FALSE.
    *
    * @return \Drupal\migrate\Plugin\MigrateDestinationInterface
    *   The destination plugin.
@@ -153,10 +154,10 @@ public function getDestinationPlugin($stub_being_requested = FALSE);
   public function getIdMap();
 
   /**
-   * The current value of the high water mark.
+   * Returns the current value of the high water mark.
    *
-   * The high water mark defines a timestamp stating the time the import was last
-   * run. If the mark is set, only content with a higher timestamp will be
+   * The high water mark defines a timestamp stating the time the import was
+   * last run. If the mark is set, only content with a higher timestamp will be
    * imported.
    *
    * @return int
@@ -165,7 +166,7 @@ public function getIdMap();
   public function getHighWater();
 
   /**
-   * Save the new high water mark.
+   * Saves the new high water mark.
    *
    * @param int $high_water
    *   The high water timestamp.
@@ -173,7 +174,7 @@ public function getHighWater();
   public function saveHighWater($high_water);
 
   /**
-   * Check if all source rows from this migration have been processed.
+   * Checks if all source rows from this migration have been processed.
    *
    * @return bool
    *   TRUE if this migration is complete otherwise FALSE.
@@ -181,15 +182,15 @@ public function saveHighWater($high_water);
   public function allRowsProcessed();
 
   /**
-   * Set the current migration status.
+   * Sets the current migration status.
    *
-   * @param int $result
+   * @param int $status
    *   One of the STATUS_* constants.
    */
   public function setStatus($status);
 
   /**
-   * Get the current migration status.
+   * Gets the current migration status.
    *
    * @return int
    *   The current migration status. Defaults to STATUS_IDLE.
@@ -197,7 +198,7 @@ public function setStatus($status);
   public function getStatus();
 
   /**
-   * Retrieve a label for the current status.
+   * Retrieves a label for the current status.
    *
    * @return string
    *   User-friendly string corresponding to a STATUS_ constant.
@@ -205,7 +206,7 @@ public function getStatus();
   public function getStatusLabel();
 
   /**
-   * Get the result to return upon interruption.
+   * Gets the result to return upon interruption.
    *
    * @return int
    *   The current interruption result. Defaults to RESULT_INCOMPLETE.
@@ -218,8 +219,9 @@ public function getInterruptionResult();
   public function clearInterruptionResult();
 
   /**
-   * Signal that the migration should be interrupted with the specified result
-   * code.
+   * Signals that the migration should be interrupted.
+   *
+   * The migration will be interrupted with the specified result code.
    *
    * @param int $result
    *   One of the MigrationInterface::RESULT_* constants.
@@ -227,8 +229,7 @@ public function clearInterruptionResult();
   public function interruptMigration($result);
 
   /**
-   * Get the normalized process pipeline configuration describing the process
-   * plugins.
+   * Gets process pipeline configuration describing the process plugins.
    *
    * The process configuration is always normalized. All shorthand processing
    * will be expanded into their full representations.
@@ -251,7 +252,7 @@ public function getProcess();
   public function setProcess(array $process);
 
   /**
-   * Set the process pipeline configuration for an individual destination field.
+   * Sets process pipeline configuration for an individual destination field.
    *
    * This method allows you to set the process pipeline configuration for a
    * single property within the full process pipeline configuration.
@@ -267,7 +268,7 @@ public function setProcess(array $process);
   public function setProcessOfProperty($property, $process_of_property);
 
   /**
-   * Merge the process pipeline configuration for a single property.
+   * Merges the process pipeline configuration for a single property.
    *
    * @param string $property
    *   The property of which to merge the passed in process pipeline
@@ -277,14 +278,13 @@ public function setProcessOfProperty($property, $process_of_property);
    *   pipeline configuration.
    *
    * @return $this
-   *   The migration entity.
    *
    * @see Drupal\migrate_drupal\Plugin\migrate\load\LoadEntity::processLinkField()
    */
   public function mergeProcessOfProperty($property, array $process_of_property);
 
   /**
-   * Get the current system of record of the migration.
+   * Gets the current system of record of the migration.
    *
    * @return string
    *   The current system of record of the migration.
@@ -292,7 +292,7 @@ public function mergeProcessOfProperty($property, array $process_of_property);
   public function getSystemOfRecord();
 
   /**
-   * Set the system of record for the migration.
+   * Sets the system of record for the migration.
    *
    * @param string $system_of_record
    *   The system of record of the migration.
@@ -310,7 +310,7 @@ public function setSystemOfRecord($system_of_record);
   public function isTrackLastImported();
 
   /**
-   * Set if the migration should track time of last import.
+   * Sets if the migration should track time of last import.
    *
    * @param bool $track_last_imported
    *   Boolean value to indicate if the migration should track last import time.
@@ -320,7 +320,7 @@ public function isTrackLastImported();
   public function setTrackLastImported($track_last_imported);
 
   /**
-   * Get the dependencies for this migration.
+   * Gets the dependencies for this migration.
    *
    * @return array
    *   The dependencies for this migrations.
diff --git a/core/modules/migrate/src/Row.php b/core/modules/migrate/src/Row.php
index 94cb8b2..758b3fe 100644
--- a/core/modules/migrate/src/Row.php
+++ b/core/modules/migrate/src/Row.php
@@ -50,7 +50,7 @@ class Row {
   /**
    * Whether the source has been frozen already.
    *
-   * Once frozen the source can not be changed any more.
+   * Once frozen, the source can not be changed any more.
    *
    * @var bool
    */
@@ -60,8 +60,8 @@ class Row {
    * The raw destination properties.
    *
    * Unlike $destination which is set by using
-   * \Drupal\Component\Utility\NestedArray::setValue() this array contains
-   * the destination as setDestinationProperty was called.
+   * \Drupal\Component\Utility\NestedArray::setValue(), this array contains the
+   * destination as setDestinationProperty was called.
    *
    * @var array
    *   The raw destination.
@@ -86,7 +86,7 @@ class Row {
    *   An array containing the IDs of the source using the keys as the field
    *   names.
    * @param bool $is_stub
-   *   TRUE if the row being created is a stub.
+   *   (optional) TRUE if the row being created is a stub. Defaults to FALSE.
    *
    * @throws \InvalidArgumentException
    *   Thrown when a source ID property does not exist.
@@ -186,6 +186,7 @@ public function freezeSource() {
    * Clones the row with an empty set of destination values.
    *
    * @return static
+   *   The clone of the row with an empty set of destination values.
    */
   public function cloneWithoutDestination() {
     return (new static($this->getSource(), $this->sourceIds, $this->isStub()))->freezeSource();
@@ -241,7 +242,7 @@ public function getDestination() {
   /**
    * Returns the raw destination. Rarely necessary.
    *
-   * For example calling setDestination('foo/bar', 'baz') results in
+   * For example, calling setDestination('foo/bar', 'baz') results in:
    * @code
    * $this->destination['foo']['bar'] = 'baz';
    * $this->rawDestination['foo/bar'] = 'baz';
@@ -317,7 +318,7 @@ public function needsUpdate() {
   }
 
   /**
-   * Returns the hash for the source values..
+   * Returns the hash for the source values.
    *
    * @return mixed
    *   The hash of the source values.