Messaging through events and operations
Items on the Concurrency Diagram can be stimulated by event or operation messages. These messages allow tasks to communicate with each other. Items linked with classes communicate using both events and operations, but interface devices use event messages only. Events and operations are attached to message flows as follows:
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Source
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Destination
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Notes
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|---|---|---|
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Interface Device
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Class or item linked to a class
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Operations at the destination only Events in both directions
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Class or item linked to a class
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Class or item linked to a class
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Operations and events in both directions
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Class or item linked to a class
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Interface Device
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Operations at the start only Events in both directions.
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To call a new operation or send a new event
1. On the Concurrency Diagram tab, select 
for an operation message or 
for an event message.
for an operation message or for an event message.2. Click the message flow.
3. Click the destination item for the message.
 | You can also drag an existing event or operation from a Modeler pane onto your diagram. |
To change the properties of an event or operation instance
1. Right-click the event or operation on your diagram.
2. Click Instance Properties.
3. Click the Options tab in the Property pages.
4. Enter as follows:
◦ Sequence Number —in Dewey decimal format. Letters indicate concurrent messages
◦ Result — to indicate return values
◦ Iterative — to show an iterative message
5. Click the Actual Parameters tab in the Property pages.
6. Enter as follows:
◦ Actual Parameters — to attach input parameters
To change the properties of an event or operation
1. Select the event or operation in the Modeler pane.
2. Change the required properties in the Property pages.