Thursday, July 09, 2015

Using a Parallel Gateway without a Merge in OBPM

In this blog article I give a brief explanation regarding some aspect of the behavior of the parallel gateway in Oracle BPM. It has been changed on September 15 2015 by adding the remark at the end regarding a Complex Merge (thanks to Martien van den Akker).

For the BPMN modelers among us, I have a small quiz.

Given a process model like this, what would be the behavior of Oracle BPM?

  1. It does not compile because OBPM thinks it is not valid BPMN
  2. The flows with Activity 1 and 2 are merged, the token moves to the End event of the process, and then the instance finishes.
  3. Activity 1 and 2 are executed, and then OBPM waits in the merge because to continue all tokens have to reach the merge.
  4. The flows with Activity 1 and 2 are merged, the token moves to the End event of the process, and in the meantime waits until the timer expires. It will not end before the token reached the Terminate end event, because not all flows from the split are explicitly merged the whole process itself serves as an implicit merge.

If this would be some magazine, I would now tell you to go to the last page and turn it upside down to read the answer. Or wait until the next issue in which I announce the prize winners.

Alas, no such thing here so let me give you the answer straight away, which is answer 4:

I must admit I was a bit surprised, as I seem to remember that some bundle patches or patch sets ago it would have been a. But when you look at the BPMN specification there is nothing that says that a parallel gateway always has to have a merge. Strange then that OBPM does not let you draw a model without one, but at least it works with a merge with just one ingoing flow.

As a matter of fact, to make the End even actually end the instance, you should change it into an Intermediate Message Throw event, and end the process with a Terminate End event as well. Run-time that looks awkward, because even when your process ends successfully it has the state Terminated.

Fir this reason and and perhaps because your audience might just not understand this model, specifically when it concerns a larger one, the following alternative perhaps is easier to understand. You now can choose if and which flow you want to end with a Terminate End event.

To force that the process continues after the merge, a Complex Merge is used that aborts all other pending parallel flows when the timer expires.

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