Message Flow

Message Flow is one of connection objects and represents the flows of messages sent and received between two business participants (Participants).

Overview
Message Flow represents flows of information or messages that sent and received between two business participants (humans, departments, systems, etc.). In BPMN, Pools are used to represent such two business participants. Message Flow connects to either of the followings. However, note that it can not connect Flow Objects in the same Pool.
 * Boundary of Pool
 * Flow Objects in Pool

A dotted arrow is used to represent Message Flow. At the source of an arrow, an outline circle is placed, and the head of the arrow is drawn as an outline triangle.


 * Sender of Message
 * Pool that is connected to the source of the Message Flow, or a subject of the Pool that contains Flow Object that connects to the source of the Message Flow
 * Recipient of Message
 * Pool that is pointed by the head of the arrow, or a subject of the Pool that contains Flow Object that is pointed by the head of the arrow

"Message contents" that are to be written above Message Flow, which also can be omitted, should be expressed in a succinct manner. E.g. "Approval," "Application," "Response," "Completion Report," "Deadline Notice," etc.

Connection to Boundary of Pool
Message Flow can connect to the boundary of Pool even when the Pool does not contain the detail of the process in it ("Black box").

In the figure on the right, it corresponds to the message exchange between B and C.

Connection beyond Boundary of Pool
Message Flow can connect to Flow Object in Pool beyond the boundary of the Pool.

In a figure on the right, it corresponds to the message exchange between A and B1.

Message Flow can also connect to a boundary of an expanded Sub-Process.
 * If a connected Message Flow is an input Message Flow, it is equivalent to Message Flow connected to Start Event in the Sub-Process.
 * If a connected Message Flow is an output Message Flow, it is equivalent to Message Flow connected to End Event in the Sub-Process.

Related Articles

 * BPMN
 * Activity
 * Flow
 * Sequence Flow
 * Swimlane
 * Pool

Reference

 * BPMN1.1 Specification (2008-01-17)