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umlactivity-diagram

Merge node in activity diagram

I'm learning Activity diagram in UML and now I'm confused with the following diagram for representing procedures when calling a pizza.enter image description here

I think a merge node should be added before the join node because if not, the join node will wait forever. Is that correct? Thank you.

Solution

  • I think you are right.

    There should be a merge node merging the two flows coming from the decision right after Ask for toppings and a merge node to merge the two flows that have been split by the decision right after Deliver Pizza

    A join node will only continue if it gets a token from all incoming flows, which will never happen if those flows are mutually exclusive because of a decision earlier on.