A First BPMN 2.0 Choreography Model
This is a first Choreograpy model. It consists of two Choreography Tasks.
The first Choreography Task is Request Booking as an interaction between two participants – the Runway Show Management and the Venue Provider. We know from the coloring that the Runway Show Management is the initiator of this interaction. We also know, that at least one message must be exchanged between the participants in the course of the interaction, maybe more.
The second Choreography Task is Confirm Booking. Here the same participants are interacting as before. So we see, that the participants are part of the Choreography model and can be referenced by different Choreography Tasks. However in the second Choreography Task the Venue provider is the initiator of the interation.
We know from the sequence flows between the Choreography Tasks, that the Confirm Booking Task follows after the Request Booking Task.
Is there a reason why the distinction between sending and receiving participants is realized via coloring? Wouldn’t it be more intuitive (and more readable in a huge diagram) to always have the sender on top and the receiver at the bottom of the task?
The reason is most probably the merged view, where collaborations are merged with the choreography. In this case the pool of one participant is on one side and of the other on the other side. Then it is much easier to connect the message flows, if all participants on the choreography tasks are on the same side.
A small remark: It is not about sender or receiver, but about initiator of the task. There could be more message exchanges related to a choreography task than one, in which case the sender and receiver would be the other way round. But the initiator is still the same. So initiator is a nontechnical term in contrast to sender or receiver.