Metamodel user guide
the Start Event indicates where a particular Process will start. In terms of Sequence Flow, the Start Event starts the flow of the Process, and thus, will not have any incoming Sequence Flow?no Sequence Flow can connect to a Start Event.
Figure 59 : StartEvent class diagram
|boolean IsInterrupting [1..1]|
This attribute only applies to Start Events of Event Sub-Processes; it is ignored for other Start Events. This attribute denotes whether the Sub-Process encompassing the Event Sub-Process should be cancelled or not, If the encompassing Sub-Process is not cancelled, multiple instances of the Event Sub-Process can run concurrently. This attribute cannot be applied to Error Events (where it?s always true), or Compensation Events (where it doesn?t apply).
A Start Event MUST NOT be a target for Sequence Flow; it MUST NOT have incoming Sequence Flow. An exception to this is when a Start Event is used in an Expanded Sub-Process and is attached to the boundary of that Sub-Process. In this case, a Sequence Flow from the higher-level Process MAY connect to that Start Event in lieu of connecting to the actual boundary of the Sub-Process. A Start Event MUST be a source for Sequence Flow. The Trigger attribute of the Start Event MUST be set to Message or Multiple if there are any incoming Message Flow. The Trigger attribute of the Start Event MUST be set to Multiple if there is more than one (1) incoming Message Flow.