Combined fragments

In Unified Modeling Language (UML) sequence diagrams, combined fragments define conditional structures in interactions.

A combined fragment defines an expression of interaction fragments. A combined fragment is defined by an interaction operator and its corresponding interaction operands. You can use combined fragments to describe several traces in a compact and concise manner.

A combined fragment consists of an interaction operator, one or more interaction operands, and an optional guard condition.

As the following figure illustrates, a combined fragment is displayed as a frame that covers lifelines and contains interaction operands. A combined fragment separates the contained interaction operands with a dashed horizontal line between each operand.

This interaction frame shows two lifelines with two combined fragments crossing the lifelines. The first loop combined fragment has one interaction operand and a guard condition. The second alt combined fragment has two interaction operands, each with a guard condition.

Related concepts
Lifelines
Messages
Execution occurrences
Interaction occurrences
Related tasks
Creating combined fragments
Resizing interaction fragments
Adding interaction operands to combined fragments
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