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.

: BpmnStartEvent (architecture_autodiagram)
Figure 41 : BpmnStartEvent (architecture_autodiagram)
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).