diff --git a/core/lib/Drupal/Core/Plugin/ConfigurablePluginInterface.php b/core/lib/Drupal/Component/Plugin/ConfigurablePluginInterface.php
similarity index 83%
rename from core/lib/Drupal/Core/Plugin/ConfigurablePluginInterface.php
rename to core/lib/Drupal/Component/Plugin/ConfigurablePluginInterface.php
index ea959f4..3c500ea 100644
--- a/core/lib/Drupal/Core/Plugin/ConfigurablePluginInterface.php
+++ b/core/lib/Drupal/Component/Plugin/ConfigurablePluginInterface.php
@@ -2,10 +2,10 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Plugin\ConfigurablePluginInterface.
+ * Contains \Drupal\Component\Plugin\ConfigurablePluginInterface.
  */
 
-namespace Drupal\Core\Plugin;
+namespace Drupal\Component\Plugin;
 
 /**
  * Provides an interface for a configurable plugin.
diff --git a/core/lib/Drupal/Core/Plugin/DefaultPluginBag.php b/core/lib/Drupal/Component/Plugin/DefaultPluginBag.php
similarity index 92%
rename from core/lib/Drupal/Core/Plugin/DefaultPluginBag.php
rename to core/lib/Drupal/Component/Plugin/DefaultPluginBag.php
index 2d301f5..60af300 100644
--- a/core/lib/Drupal/Core/Plugin/DefaultPluginBag.php
+++ b/core/lib/Drupal/Component/Plugin/DefaultPluginBag.php
@@ -2,15 +2,14 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Plugin\DefaultPluginBag.
+ * Contains \Drupal\Component\Plugin\DefaultPluginBag.
  */
 
-namespace Drupal\Core\Plugin;
+namespace Drupal\Component\Plugin;
 
 use Drupal\Component\Plugin\Exception\PluginException;
-use Drupal\Component\Plugin\PluginBag;
-use Drupal\Component\Plugin\PluginManagerInterface;
 use Drupal\Component\Utility\MapArray;
+use Drupal\Component\Utility\String;
 
 /**
  * Provides a default plugin bag for a plugin type.
@@ -69,7 +68,7 @@ protected function initializePlugin($instance_id) {
     if (!isset($this->pluginInstances[$instance_id])) {
       $configuration = $this->configurations[$instance_id];
       if (!isset($configuration[$this->pluginKey])) {
-        throw new PluginException(format_string("Unknown plugin ID '@instance'.", array('@instance' => $instance_id)));
+        throw new PluginException(String::format("Unknown plugin ID '@instance'.", array('@instance' => $instance_id)));
       }
       $this->pluginInstances[$instance_id] = $this->manager->createInstance($configuration[$this->pluginKey], $configuration);
       $this->addInstanceID($instance_id);
diff --git a/core/lib/Drupal/Core/Plugin/DefaultSinglePluginBag.php b/core/lib/Drupal/Component/Plugin/DefaultSinglePluginBag.php
similarity index 90%
rename from core/lib/Drupal/Core/Plugin/DefaultSinglePluginBag.php
rename to core/lib/Drupal/Component/Plugin/DefaultSinglePluginBag.php
index 2bfb612..023ba3e 100644
--- a/core/lib/Drupal/Core/Plugin/DefaultSinglePluginBag.php
+++ b/core/lib/Drupal/Component/Plugin/DefaultSinglePluginBag.php
@@ -2,13 +2,11 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Plugin\DefaultSinglePluginBag.
+ * Contains \Drupal\Component\Plugin\DefaultSinglePluginBag.
  */
 
-namespace Drupal\Core\Plugin;
+namespace Drupal\Component\Plugin;
 
-use Drupal\Component\Plugin\PluginBag;
-use Drupal\Component\Plugin\PluginManagerInterface;
 use Drupal\Component\Utility\MapArray;
 
 /**
diff --git a/core/lib/Drupal/Core/Action/ActionBag.php b/core/lib/Drupal/Core/Action/ActionBag.php
index 7d49b4b..de0e1d7 100644
--- a/core/lib/Drupal/Core/Action/ActionBag.php
+++ b/core/lib/Drupal/Core/Action/ActionBag.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Action;
 
-use Drupal\Core\Plugin\DefaultSinglePluginBag;
+use Drupal\Component\Plugin\DefaultSinglePluginBag;
 
 /**
  * Provides a container for lazily loading Action plugins.
diff --git a/core/lib/Drupal/Core/Action/ConfigurableActionBase.php b/core/lib/Drupal/Core/Action/ConfigurableActionBase.php
index 0d4c021..25fe32f 100644
--- a/core/lib/Drupal/Core/Action/ConfigurableActionBase.php
+++ b/core/lib/Drupal/Core/Action/ConfigurableActionBase.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Action;
 
-use Drupal\Core\Plugin\ConfigurablePluginInterface;
+use Drupal\Component\Plugin\ConfigurablePluginInterface;
 use Drupal\Core\Action\ActionBase;
 use Drupal\Core\Plugin\PluginFormInterface;
 
diff --git a/core/modules/block/lib/Drupal/block/BlockPluginBag.php b/core/modules/block/lib/Drupal/block/BlockPluginBag.php
index 3bdb911..7807034 100644
--- a/core/modules/block/lib/Drupal/block/BlockPluginBag.php
+++ b/core/modules/block/lib/Drupal/block/BlockPluginBag.php
@@ -10,7 +10,7 @@
 use Drupal\Component\Plugin\Exception\PluginException;
 use Drupal\Component\Plugin\PluginManagerInterface;
 use Drupal\Component\Utility\String;
-use Drupal\Core\Plugin\DefaultSinglePluginBag;
+use Drupal\Component\Plugin\DefaultSinglePluginBag;
 
 /**
  * Provides a collection of block plugins.
diff --git a/core/modules/block/lib/Drupal/block/BlockPluginInterface.php b/core/modules/block/lib/Drupal/block/BlockPluginInterface.php
index a5c4f52..86a7644 100644
--- a/core/modules/block/lib/Drupal/block/BlockPluginInterface.php
+++ b/core/modules/block/lib/Drupal/block/BlockPluginInterface.php
@@ -8,7 +8,7 @@
 namespace Drupal\block;
 
 use Drupal\Component\Plugin\PluginInspectionInterface;
-use Drupal\Core\Plugin\ConfigurablePluginInterface;
+use Drupal\Component\Plugin\ConfigurablePluginInterface;
 use Drupal\Core\Plugin\PluginFormInterface;
 
 /**
diff --git a/core/modules/filter/lib/Drupal/filter/FilterBag.php b/core/modules/filter/lib/Drupal/filter/FilterBag.php
index 3e7cec6..8de6646 100644
--- a/core/modules/filter/lib/Drupal/filter/FilterBag.php
+++ b/core/modules/filter/lib/Drupal/filter/FilterBag.php
@@ -9,7 +9,7 @@
 
 use Drupal\Component\Plugin\Exception\PluginException;
 use Drupal\Component\Utility\NestedArray;
-use Drupal\Core\Plugin\DefaultPluginBag;
+use Drupal\Component\Plugin\DefaultPluginBag;
 
 /**
  * A collection of filters.
diff --git a/core/modules/filter/lib/Drupal/filter/Plugin/FilterInterface.php b/core/modules/filter/lib/Drupal/filter/Plugin/FilterInterface.php
index 432201c..ee4ba2b 100644
--- a/core/modules/filter/lib/Drupal/filter/Plugin/FilterInterface.php
+++ b/core/modules/filter/lib/Drupal/filter/Plugin/FilterInterface.php
@@ -8,7 +8,7 @@
 namespace Drupal\filter\Plugin;
 
 use Drupal\Component\Plugin\PluginInspectionInterface;
-use Drupal\Core\Plugin\ConfigurablePluginInterface;
+use Drupal\Component\Plugin\ConfigurablePluginInterface;
 
 /**
  * Defines the interface for text processing filter plugins.
diff --git a/core/modules/image/lib/Drupal/image/ImageEffectBag.php b/core/modules/image/lib/Drupal/image/ImageEffectBag.php
index 11f173b..b892675 100644
--- a/core/modules/image/lib/Drupal/image/ImageEffectBag.php
+++ b/core/modules/image/lib/Drupal/image/ImageEffectBag.php
@@ -9,7 +9,7 @@
 
 use Drupal\Component\Utility\MapArray;
 use Drupal\Component\Uuid\Uuid;
-use Drupal\Core\Plugin\DefaultPluginBag;
+use Drupal\Component\Plugin\DefaultPluginBag;
 
 /**
  * A collection of image effects.
diff --git a/core/modules/image/lib/Drupal/image/ImageEffectInterface.php b/core/modules/image/lib/Drupal/image/ImageEffectInterface.php
index d2a08b8..19575e9 100644
--- a/core/modules/image/lib/Drupal/image/ImageEffectInterface.php
+++ b/core/modules/image/lib/Drupal/image/ImageEffectInterface.php
@@ -8,7 +8,7 @@
 namespace Drupal\image;
 
 use Drupal\Component\Plugin\PluginInspectionInterface;
-use Drupal\Core\Plugin\ConfigurablePluginInterface;
+use Drupal\Component\Plugin\ConfigurablePluginInterface;
 
 /**
  * Defines the interface for image effects.
diff --git a/core/modules/system/lib/Drupal/system/Plugin/Core/Entity/Action.php b/core/modules/system/lib/Drupal/system/Plugin/Core/Entity/Action.php
index b66c2d8..07591aa 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/Core/Entity/Action.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/Core/Entity/Action.php
@@ -13,7 +13,7 @@
 use Drupal\Core\Entity\EntityStorageControllerInterface;
 use Drupal\system\ActionConfigEntityInterface;
 use Drupal\Core\Action\ActionBag;
-use Drupal\Core\Plugin\ConfigurablePluginInterface;
+use Drupal\Component\Plugin\ConfigurablePluginInterface;
 
 /**
  * Defines the configured action entity.
diff --git a/core/modules/tour/lib/Drupal/tour/TipsBag.php b/core/modules/tour/lib/Drupal/tour/TipsBag.php
index dc49a17..275d152 100644
--- a/core/modules/tour/lib/Drupal/tour/TipsBag.php
+++ b/core/modules/tour/lib/Drupal/tour/TipsBag.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\tour;
 
-use Drupal\Core\Plugin\DefaultPluginBag;
+use Drupal\Component\Plugin\DefaultPluginBag;
 
 /**
  * A collection of tips.
diff --git a/core/modules/views/lib/Drupal/views/DisplayBag.php b/core/modules/views/lib/Drupal/views/DisplayBag.php
index 18aec89..167212e 100644
--- a/core/modules/views/lib/Drupal/views/DisplayBag.php
+++ b/core/modules/views/lib/Drupal/views/DisplayBag.php
@@ -9,7 +9,7 @@
 
 use Drupal\Component\Plugin\Exception\PluginException;
 use Drupal\Component\Plugin\PluginManagerInterface;
-use Drupal\Core\Plugin\DefaultPluginBag;
+use Drupal\Component\Plugin\DefaultPluginBag;
 
 /**
  * A class which wraps the displays of a view so you can lazy-initialize them.