UML 2.0 in a Nutshell

Alternate Interaction Notations

UML provides several notations for capturing interactions. The first part of this chapter used the sequence diagram notation. The remainder of this chapter describes the other notations available and when they may be more appropriate than sequence notation.

Figure 10-36. The final sequence, with all continuations expanded

Communication Diagrams

Communication diagrams allow you to focus on the elements involved in interactions rather than the detailed sequencing and flow control allowed in sequence diagrams. Most UML tools can automatically convert from a sequence diagram to a communication diagram; however, because communication diagrams aren't as expressive,.some information may be lost.

When you're modeling with communication diagrams, objects are represented by a rectangle, and connections between objects are shown as a solid line. Each message has a sequence number and a small arrow indicating the direction of the message along a given connection. Communication diagrams can't show message overtaking (see Figure 10-6 earlier in the chapter) or interaction fragments.

Figure 10-38 shows a simple sequence diagram and the equivalent communication diagram.

The syntax for a message name is:

               
    sequence_number: name [ recurrence_or_guard ]

Figure 10-37. A sequence ...