Message Flow

A process can exchange information with external entities or processes via message flow. A message flow shape, the dashed arrow connector, must connect to a message node in a process at one end and either a message node in another process or a black-box pool at the other end. Message nodes include a Message event, User task, Send task, Receive task, subprocess, or Call Activity. Most of the time, the external entity or process is represented by a black-box pool. A message flow may not connect two nodes in the same process.

The label of a message flow indicates the name of the message, i.e., the information being sent.

In non-executable models, the message flow to a Message start event represents an external request to initiate the process. In most executable models, that request is represented instead by a data input. In Workflow Modeler, executable models may use message flows to represent asynchronous service calls to or from the process.

In Method and Style, which applies to non-executable models, message flows to or from a collapsed subprocess in a parent-level diagram are replicated in the child-level diagram, where they connect to a message node in the child level flow. Also, message flows must be drawn to any Message event, Send or Receive task.

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