BPMN - Collaboration diagram one pool?

Question

I'd like to ask you a question about Collaboration diagrams.

Unfortunately I cant find anywhere answer to my question. During our classes I was shown collaboration process, that used connection between various activities, gates etc. But on those there wasn't any pool displayed. It's only showed with logical diagram of an activity (Start Event-> Dress up->Is it raining?)

But when I was studying from various online websites they had always 2 or more pools. One pool for each Business process.

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My question is.

Is it possible to have a communication diagram without any pool (or even 1 pool)?

Answer 1

Technically, a collaboration diagram usually contains two or more Pools (BPMN 2.0 specification page 110/140 in PDF), but a Process that represents the work performed from the point of view of the modeler or the modeler's organization can be considered “internal” and is NOT REQUIRED to be surrounded by the boundary of the Pool (page 112/142 in PDF). This means having only one pool in a collaboration diagram is possible. However, one wouldn't consider a process diagram with only one pool and no inter-pool communication (or no pool at all) a collaboration diagram, but rather a process diagram.

On a more practical note, most BPM(N) vendors and practitioners don't distinguish between collaboration and process diagrams and refer to BPMN diagrams generally as process diagrams. Also, it's very common (but not necessarily good practice) to not model any pool to keep things simple.