diff --git a/src/vs/workbench/common/composite.ts b/src/vs/workbench/common/composite.ts
new file mode 100644
index 0000000000000000000000000000000000000000..9bb4aa4e868345ca1f737e8b8d6c89db8d757564
--- /dev/null
+++ b/src/vs/workbench/common/composite.ts
@@ -0,0 +1,51 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import {IEventEmitter} from 'vs/base/common/eventEmitter';
+import {IAction, IActionItem} from 'vs/base/common/actions';
+import {ISelection} from 'vs/platform/selection/common/selection';
+
+export interface IComposite {
+
+	/**
+	 * Returns the unique identifier of this composite.
+	 */
+	getId(): string;
+
+	/**
+	 * Returns the name of this composite to show in the title area.
+	 */
+	getTitle(): string;
+
+	/**
+	 * Returns the primary actions of the composite.
+	 */
+	getActions(): IAction[];
+
+	/**
+	 * Returns the secondary actions of the composite.
+	 */
+	getSecondaryActions(): IAction[];
+
+	/**
+	 * Returns the action item for a specific action.
+	 */
+	getActionItem(action: IAction): IActionItem;
+
+	/**
+	 * Returns the underlying control of this composite.
+	 */
+	getControl(): IEventEmitter;
+
+	/**
+	 * Returns the selection of this composite.
+	 */
+	getSelection(): ISelection;
+
+	/**
+	 * Asks the underlying control to focus.
+	 */
+	focus(): void;
+}
diff --git a/src/vs/workbench/common/viewlet.ts b/src/vs/workbench/common/viewlet.ts
index f68b45087d20d962cf1e5abccfedb3058002f00b..569f69f05a19ed85a892ebe9bc18cc4adf73756d 100644
--- a/src/vs/workbench/common/viewlet.ts
+++ b/src/vs/workbench/common/viewlet.ts
@@ -4,49 +4,6 @@
  *--------------------------------------------------------------------------------------------*/
 'use strict';
 
-import {IEventEmitter} from 'vs/base/common/eventEmitter';
-import {IAction, IActionItem} from 'vs/base/common/actions';
-import {ISelection} from 'vs/platform/selection/common/selection';
+import {IComposite} from 'vs/workbench/common/composite';
 
-export interface IViewlet {
-
-	/**
-	 * Returns the unique identifier of this viewlet.
-	 */
-	getId(): string;
-
-	/**
-	 * Returns the name of this viewlet to show in the title area.
-	 */
-	getTitle(): string;
-
-	/**
-	 * Returns the primary actions of the viewlet.
-	 */
-	getActions(): IAction[];
-
-	/**
-	 * Returns the secondary actions of the viewlet.
-	 */
-	getSecondaryActions(): IAction[];
-
-	/**
-	 * Returns the action item for a specific action.
-	 */
-	getActionItem(action: IAction): IActionItem;
-
-	/**
-	 * Returns the underlying control of this viewlet.
-	 */
-	getControl(): IEventEmitter;
-
-	/**
-	 * Returns the selection of this viewlet.
-	 */
-	getSelection(): ISelection;
-
-	/**
-	 * Asks the underlying control to focus.
-	 */
-	focus(): void;
-}
\ No newline at end of file
+export interface IViewlet extends IComposite { }