BPMN Basic Rules
A few basic rules of BPMN:
Sequence Flows
Are used to show the order that Activities will be performed in a Process
They cannot cross Sub-Process boundaries
They cannot cross Pool boundaries
Message Flows
Are used to show communication between Participants
They cannot connect objects that are within the same Pool
Boundary Events
✪ Must have at most one outgoing Sequence Flow
Must not have any incoming Sequence Flow
Sub-Process
✪ A Start Event in a Sub-Process must be of type None