Added output message format.

Author: ashcrow

messageformats.rst

@@ -8,3 +8,4 @@ Message Formats
 .. include:: messageformats/rerest-recore.rst
 .. include:: messageformats/recore-reworkers.rst
 .. include:: messageformats/notification.rst
+.. include:: messageformats/output.rst

messageformats/output.rst

@@ -0,0 +1,21 @@
+Output Message Format
+----------------------
+
+.. _output_message_format:
+
+Notifications are sent out by workers connected to the Release Engine and follow a standard and very simple message format. This format is then consumed by the output worker who turns the standard format into messages in a file.
+
+The Output Message Format has 1 key: message. The only other bit of information needed by an output worker is the correlation id which happens to be stored in the AMQP properties.
+
+**Required Keys**:
+
+* message: The message which should be written to a file.
+
+
+**Example**:
+
+.. code-block:: json
+
+   {
+       "message": "Something happened and you should know about it"
+   }