Lecture 4: Advanced BPMN

Question 1

Messages, delays, and racing conditions

Answer 1

Message Events: denote message start, intermediate and endevents

Temporal Events: denotes a planned or expected delay in the process

Racing Conditions (event-based XOR split): used when external events trigger different internal paths

Question 2

Rework using Exclusive (XOR) Gateway

Answer 2

The simplest way to model rework is by using XOR gateways. The drawback is the possible infinite loop (potentially fatal when simulating)

Question 3

Looped subprocesss

Answer 3

• BPMN is not ideal for feedback loops and repititions (rememeber it is a deterministic, linear modelling notation)
• But can be forced to accept simple loops and cycles

Question 4

Parallel repetition

Answer 4

Captures sequential repetition for a limited number of iterations; denoted by using parallel (AND) split and merge to allow separate tasks to be chosen

Question 5

Uncontrolled repetition

Answer 5

One or more activities are repeated a number of times until a condition is met.

!!! not supported in simulation and rarely used in modelling

Looks like nesting with tilde at bottom

Question 6

What are exceptions

Answer 6

• Exceptions are events that deviate a process from its normal course, i.e. “sunny-day” scenario
• Exceptions cause interruption or abortion of the running process
• Exceptions can be triggered by:
  
  • Business faults e.g. out-of-stock or discontinued product
  • Technology faults e.g. database crash, internet outage

Question 7

Process abortion

Answer 7

Processes can be aborted using an end terminate event that destroys all tokens in the process model and in any sub-process

Question 8

Internal exceptions

Answer 8

• We can also interrupt just the specific activity that has caused the exception, instead of aborting the whole process
• Full lightning (error event) will throw the exception, empty lightning (boundaryevent) will catch it
• All tokens in sub-process removed, one token goes through exception flow to end event

Question 9

External exceptions

Answer 9

• Exceptions may also be caused by an external event occurring during an activity
• E.g. order cancellation during stock availability check
• Called unsolicited exceptions since they originate externally to the process

Question 10

Non-interrupting events and complex exceptions

Answer 10

External events that trigger a procedure without interrupting the process. Denoted by a dashed double border instead of normal double border