How to model message flows in subprocess?

Ilze,

why do you think that the behaviour in ARIS is not compliant to the spec ("for me it seems that such restiction is not BPMN compliant as sure that BPMN allows message flow to cross boundaries of sub-process")?

I checked the spec yesterday (and also the non-normative "BPMN by example" PDF) and in no graphic a message is sent to an object within a subprocess.

This makes sense to me, because the subprocess "hides" all steps within it when collapsed and acts as a black box. Another sign of that is that every process within a subprocess has to start with a none start event - this shows me that all things within are capsuled, even though on the higher level you might have a start event that is different.

If you want to show lower level/higher level interaction, you have to model like this IMHO (which is consistent with the modeling style of showing 2 SP end events on a higher level again after a gateway).

Hello,

I think it is just a matter of interpretation of notation.

You are right that is not specifically allowed in BPMN v2.0, as well as in general it is not also specifically perhibited (only for specific types of sub-processes).

But it was specifically allowed in BPMN v1.2, that message flow can be directly attached to objects inside sub-process.

As due to continuity I would still interpret that in general it is allowed, where it is not specifically perhibited.

Also from practical point of view, if it is not allowed, basically it means that it excludes option to model in subprocess objects which sends/received message, as it is not clearly readable anymore from/to where message flow comes, especially if there are sevelar such receive/send objects in sub-process. it limits modelling options.

if it is not really possible, a good thing would be if message flows would stay in attached places to sub-process boundary after collapsing and expanding, and not change its initial location, it would help atleast a bit add readability.

ps. thank you for your advice on how end send event can be used, I will see where I can apply it.

BR,

Ilze

Hi Ilze,

BPMN 2 is not an upgrade of BPMN 1.2, but a standard on its own. So BPMN 2 only allows what is written in the document and not something which was allowed in BPMN 1.2 and is now not explicitly forbidden. That's just not how this standard works.

Hello,

Roland, in example 12 (the email-voting example) in "BPMN by example" there are several message flows attached to objects (start events and tasks) within sub processes.

How do these subprocesses look like when they are collapsed?

Cheers

Ingo

@Ingo - besides that I find this model horrible and not "still be easily understandable for readers of the Diagram" as stated in the introduction of that chapter, I found the message flows too. I will talk with our BPMN gurus, since this is an inconsistent behavior IMHO (not that there are no other inconsistencies/multiple ways to do the same thing in the spec).

The only answer I can give you for now is that this document is non-normative and the spec itself doesn't show this behavior/example. In the end it is the spec that is the baseline for the implementation.

Ingo,

E-mail voting example is notorious. First for its modelling style. A whole chapter (p.193) in BPMN 2.0 Handbook  is devoted on improving exactly that model. Then data input contradicts specification. And then message flows crossing sub-process boundary is for me clearly non-compliant. If you need message flows to/from elements within a sub-process then you need to make it global and call it from the 'parent' (actually no longer a real parent). The same if you need to have lanes. But again, as it was with your pointer to the e-mail voting, you can see lanes in a sub-process in diagrams by some very authoritative sources, example in page 87 of the Handbook.

Roland & Ivo,

many thanks for your quick answers. I think global (sub-)processes will help in my case. Could you please describe in short how to model a message flow into/from a global sub-process or is this all done via events?

EDIT:

I used the wrong diagram, it has to be collaboration instead of process diagram.

Regards

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Hello,

I tried to draw a message flow between message event/trigger in BPMN 2.0 diagram using ARIS Businesss Architect 7.2.

1. it does not draw message flow as "dash line".

2. it draws in the wrong direction (i.e.: from receive/start message event to end message event.)

3. it cannot draw message flow from blackbox pool to anywhere in the next pool.

Am I doing it wrong?

Is there an Issue or Bug, especially in ARIS Architect 7.2?

Do I use the wrong software?

Which ARIS product should I use to draw Business Process Model using BPMN 2.0?

Push, can you please post a screenshot of the wrong model? It is hard to guess if you can't see it. Which BPMN model type do you use? BPMN 2 or 1.x - there are semantic differences in the specs.

Hello Roland,

the problem is already solved. At the beginning of "Create new model", I started from BPMN 2.0 process diagram instead of BPMN 2.0 collaboration diagram.
I found somewhere in this forum, if we want to start diagram that has communication between pools, on the "create new model" has to be started with "Collaboration Diagram"
Now I can draw message flow normally.

I found the discussion thoroughly confusing. If what you are saying is a correct interpretation of the standard then we are effectively saying that message tasks and events cannot be used in any sub process level. That cannot be correct. Yes, a subprocess is to a certain extent encapsulated, so a message flow should also be visible on the boundary of the parent activity, but if I want to communicate with an external party (black box pool on this case) I obviously can do that from any process level.