Describe the different Timer Events that are used in BPMN.

There are 4 variations of Time Event symbols that can be used in BPMN.  Before describing how each is used, a quick reminder of the overall BPMN Event Notation is helpful.  

The 4 BPMN Timer Event types are:
Timer Start Event, Interrupting 
Timer Start Event, Non-Interrupting 
Timer Intermediate Event, Interrupting 
Timer Intermediate Event, Non-Interrupting 

BPMN Timer Events
All 4 of these Timer Events are “Catching Events” meaning they are waiting for a trigger before emitting a token and allowing flow to proceed down a particular path.

So how does each Timer Event work and under what conditions are they used?

A Timer event  can represent a specific point in time (Each morning at 9am, the 30th of the month at 10pm, etc.) or it can be used to represent a time span or passage of time (5 mins, 3 hours, 15 days, etc.)
BPMN Timer Start Event
Timer Start Events (represented as a timer inside a single thin circle) kick off a process once the Timer Event is triggered while Timer Intermediate Events are used within a process that is already underway to redirect the flow of a process.  

An interrupting event is more common that a non-interrupting event.  As the name implies, once triggered, the current task stops and the flow of control continues along the new path.  This is shown in the diagram below. 
BPMN Boundary Event
In the case of an Non-Interrupting Timer Event (represented as a timer inside one or two dashed circles) subprocess A will not be interrupted.  Subprocess A will complete and the flow will continue on to subprocess B while a parallel flow will continue from the Non-Interrupting Timer Event onto the Handle Timeout subprocess. 

posted @ Friday, April 5, 2013 7:00 PM by Chris Adams