BPMN: send message from within business process

[yoozd]

In our BPMN models we use Business process elements to manage the complexity of our business process models: we can show business process element in 'expanded' state ('Show composite diagram' option is selected) to show the complete detailed process and in 'collapsed' state for some communication purposes.

The problem I'm having is that it seems that it's not possible to send messages (that is: message flow) from within a business process element to a different pool/lane/business process or to an intermediate event within another process.

When I collapse a business process element I'd like to see the communication (message flow and sequence flow) that all elements within the business process have with the surrounding business processes. When the business process element is expanded I'd like to see how the contained elements communicatie (message flow and sequence flow) with their surroundings.