Roman:
You are touching upon a very important but seldom recognized problem: complex business systems, especially at higher levels of abstraction, are notorious for having non-sequential processes (or steps). A BA can not model non-sequential processes using a sequence based technique.
With just one non-sequence-based process, you can pretty much improvize a work around. But if you have many, a general rule: Use Data Flow Diagram for modeling business systems at higher levels of abstraction and use sequenece based techniques at the detail leve, where just about all processes can be displayed in some sort of sequencel.
Tony
To handle the non-sequence process inside the sequence based model, you may need to encapsulate it in an ad hoc subprocess. If a seemingly random event can occur at any time, make an exception path and limit the domain of when it can be triggered.
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