Update route information about outputs

Author: kgremban

articles/iot-edge/module-composition.md

@@ -4,7 +4,7 @@ description: Learn how a deployment manifest declares which modules to deploy, h
 author: kgremban
 manager: philmea
 ms.author: kgremban
-ms.date: 03/28/2019
+ms.date: 05/28/2019
 ms.topic: conceptual
 ms.service: iot-edge
 services: iot-edge
@@ -129,15 +129,17 @@ Every route needs a source and a sink, but the condition is an optional piece th
 
 ### Source
 
-The source specifies where the messages come from. IoT Edge can route messages from leaf devices or modules.
+The source specifies where the messages come from. IoT Edge can route messages from modules or leaf devices. 
+
+Using the IoT SDKs, modules can declare specific output queues for their messages using the ModuleClient class. Output queues aren't necessary, but are helpful for managing multiple routes. Leaf devices can use the DeviceClient class of the IoT SDKs to send messages to IoT Edge gateway devices in the same way that they would send messages to IoT Hub. For more information, see [Understand and use Azure IoT Hub SDKs](../iot-hub/iot-hub-devguide-sdks).
 
 The source property can be any of the following values:
 
 | Source | Description |
 | ------ | ----------- |
 | `/*` | All device-to-cloud messages or twin change notifications from any module or leaf device |
 | `/twinChangeNotifications` | Any twin change (reported properties) coming from any module or leaf device |
-| `/messages/*` | Any device-to-cloud message sent by a module or leaf device through some or no output |
+| `/messages/*` | Any device-to-cloud message sent by a module through some or no output, or by a leaf device |
 | `/messages/modules/*` | Any device-to-cloud message sent by a module through some or no output |
 | `/messages/modules/<moduleId>/*` | Any device-to-cloud message sent by a specific module through some or no output |
 | `/messages/modules/<moduleId>/outputs/*` | Any device-to-cloud message sent by a specific module through some output |