How do I illustrate both sides of a transaction in BPMN? -

How do I illustrate both sides of a transaction in BPMN? -

we have number of processes rely on interactions between 2 people/groups. trying figure out best way illustrate in bpmn.

consider: using illustration of pizza order, phone call pizzeria order, order-taker answers phone , discuss order. trying accurately capture "we discuss order" portion of process. here how envision diagram playing out. call, answer, there's branching simultaneous exchange, converges @ end of phone call , order finished. illustrated correctly? or there improve ways show 2 different entities communicating each other @ same time accomplish task?

the moment want show interaction in greater detail high level bird view, typically run troubles when remaining within paradigm of using "one pool several lanes". in such case need draw called "collaboration diagram", means create utilize of several pools , hence several process definitions interacting each other means of message exchange. give illustration here:

you may utilize envelope symbols attached message flows, don't need to.

the big advantage of approach can show processes dependent on each other, yes, each participant wants remain in drivers seat of his/her own process, e.g. deciding if other side doesn't provide desired answer, doesn't within reasonable time , on. furthermore can @ diagram both perspectives , people see "their own process" - , not mixed concerns of others involved.

for same reason bpmn offers concept of "collapsed pools" able @ communication 1 side , treat internal details of other side kind of "black box":

bpmn