Communication Diagram

A Communication diagram is a diagram that shows the interactions between elements at run-time in much the same manner as a Sequence diagram. However, Communication diagrams are used to visualize inter-object relationships, while Sequence diagrams are more effective at visualizing processing over time.

Communication diagrams employ ordered, labeled associations to illustrate processing. Numbering is important to indicate the order and nesting of processing. A numbering scheme could be:

1.1

1.1.1

1.1.2

1.2, and so on.

A new number segment begins for a new layer of processing, and would be equivalent to a method invocation.

You generate Communication diagram elements and connectors from the Communication pages of the Toolbox.

Example Diagram

This example illustrates a Communication diagram among cooperating object instances. Note the use of message levels to capture related flows, and the different colors of the messages.

Communication Diagram Element Toolbox Icons

Icon	Description	See also
	An Actor is a user of the system; user can mean a human user, a machine, or even another system or subsystem in the model.	Actor
	An Object is a particular instance of a Class at run time.	Object
	A Boundary is a stereotyped Object that models some system boundary, typically a user interface screen.	Boundary
	A Control element represents a controlling entity or manager that organizes and schedules other activities and elements.	Control
	An Entity is a stereotyped Object that models a store or persistence mechanism that captures the information or knowledge in a system.	Entity
	Packages are used to organize your project contents, but when added onto a diagram they can be use for structural or relational depictions.	Package

Communication Diagram Connector Toolbox Icons

Icon	Description	See also
	An Association implies that two model elements have a relationship, usually implemented as an instance variable in one or both Classes.	Associate
	The Nesting Connector is an alternative graphical notation for expressing containment or nesting of elements within other elements.	Nesting
	A Realizes connector represents that the source object implements or Realizes its destination object.	Realize

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