10.7 Describing Complex Scenarios Using Combined Fragments

The most basic form of an interaction is, as stated earlier, a weak sequence of occurrences—broadly speaking, read from top to bottom of the sequence diagram. However, more complex patterns of interaction can be modeled using constructs called combined fragments. Different combined fragments specify different rules for the ordering of messages and their associated occurrences such as parallel and alternative traces.

A combined fragment consists of an interaction operator and its operands. The interaction operator defines the type of ordering logic, and its operands are all subject to that rule. Each operand has a guard containing a constraint expression that indicates the conditions under ...

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