What does a par combined fragment represent in a sequence diagram?

What does a par combined fragment represent in a sequence diagram?

• A. A sequential execution of events
• B. Two or more sets of event occurrences that happen in parallel
• C. A branching choice between alternative paths
• D. A single event occurrence

Answer: (B)

In sequence diagrams, combined fragments organize how different parts of a interaction relate. The par (parallel) fragment shows that two or more sets of events occur at the same time. Each operand inside the par fragment contains its own sequence of messages, which can proceed concurrently with the others, while preserving order within each operand. There’s no fixed order between messages from different operands, which models true parallelism. That’s why this concept best fits the idea of two or more sets of event occurrences happening in parallel. The other options describe sequential flow, branching between alternatives, or a single event, none of which capture concurrent execution.

In sequence diagrams, combined fragments organize how different parts of a interaction relate. The par (parallel) fragment shows that two or more sets of events occur at the same time. Each operand inside the par fragment contains its own sequence of messages, which can proceed concurrently with the others, while preserving order within each operand. There’s no fixed order between messages from different operands, which models true parallelism.

That’s why this concept best fits the idea of two or more sets of event occurrences happening in parallel. The other options describe sequential flow, branching between alternatives, or a single event, none of which capture concurrent execution.