What is a join node?

What is a join node?

• A. Marks the end of concurrent sequences in an activity
• B. Marks the start of concurrent sequences in an activity
• C. Marks the end of alternative sequences in an activity
• D. Represents a lifeline

Answer: (A)

A join node in an activity diagram is a synchronization point that ends parallel work. It collects multiple concurrent flows that arrived from different paths and waits for all of them to complete, then continues along a single outgoing edge. This is why it marks the end of concurrent sequences in an activity: it brings the parallel activities back together before the workflow proceeds. Think of it as the point where parallel tasks that started from a fork are brought back into a single path. In contrast, starting parallel work is done by a fork node, which splits one flow into multiple parallel paths. Merging alternative paths is handled by a merge node, not a join. And lifelines belong to sequence diagrams, not to activity diagrams.

A join node in an activity diagram is a synchronization point that ends parallel work. It collects multiple concurrent flows that arrived from different paths and waits for all of them to complete, then continues along a single outgoing edge. This is why it marks the end of concurrent sequences in an activity: it brings the parallel activities back together before the workflow proceeds.

Think of it as the point where parallel tasks that started from a fork are brought back into a single path. In contrast, starting parallel work is done by a fork node, which splits one flow into multiple parallel paths. Merging alternative paths is handled by a merge node, not a join. And lifelines belong to sequence diagrams, not to activity diagrams.