multiple tokens from single branch before joining

Question

Below I have a join node which synchronize branches A and B:

         |
-----A-->|
         |
         |-->action-->
         |
-----B-->|
         |

I know join waits until receiving tokens from both A and B, but what will happen in this situation:

Tokens a1 and a2 receive from branch A before b1 which is a token from B?

Does a2 override a1?
Does join synchronize a1 and b1 and a2 must wait for b2 to be accepted?

Your second bullet is correct. – Jim L. Sep 09 '18 at 06:07 — Jim L., Sep 09 '18 at 06:07
@JimL. An answer is not a comment ;-) – qwerty_so Sep 09 '18 at 08:13 — qwerty_so, Sep 09 '18 at 08:13
I know, but I’m on my mobile phone. – Jim L. Sep 09 '18 at 08:14 — Jim L., Sep 09 '18 at 08:14

score 2 · Accepted Answer · answered Sep 09 '18 at 14:38

2

It's like Tetris if you turn your picture 90 degrees clock wise. Tokens from A and B pile up at each ControlFlow. If all ingoing flows have one token the Join takes them (the lowest Tetris layer) away and emits a single one (your Tetris score :-). The other tokens fall down one layer and the game repeats.

See also my explanation at Difference between behavior of fork/join nodes toward tokens with other nodes of Activity diagrams

answered Sep 09 '18 at 14:38

qwerty_so

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Thank you for your explanation; but do you remember where this is said in specification? – hasanghaforian Sep 09 '18 at 16:29
Read pp. 387 of UML 2.5 – qwerty_so Sep 10 '18 at 05:39
I asked another question in about `UML`: "When a token which is created by JoinNode, will be rejected?" here:https://softwareengineering.stackexchange.com/q/379265/174635. Can you see that please? – hasanghaforian Oct 02 '18 at 03:33
The current answer seems pretty decent. – qwerty_so Oct 02 '18 at 14:34

multiple tokens from single branch before joining

1 Answers1