Deferred Choice

Deferred Choice

Deferred Choice is a workflow pattern. It it used to express a situation when the action you’re going to take is not known till the point of executing it.

So, ‘‘Deferred choice’’: When the choice is deferred to the point when we execute something

• for Petri Nets, visually looks identical to Exclusive Choice
• 

Deferred Choice vs Exclusive Choice

• in Exclusive Choice after execution of $a$ you already know what activity to run
• but for the deferred choice there’s a race condition between the activities

Example

Consider a flight:

• you can either print ticket at home or check in at reception
• based on this the following procedures are different
• it’s a deferred choice: the company doesn’t know which option you chose

YAWL

In YAWL it’s possible to tell the difference between XOR-split and Deferred choice

Consider this:

• 
• we start with deferred choice:
  • both actions are enabled, and both are offered to the user
  • and the user decides what to do next
• but XOR-split is different

  • based on some variables that were set before it (itself, not the user

    ) chooses the route

    - for example, if variable dosomething is set to true, we follow the top branch

BPMN

In BMPN the deferred choice is represented by a special-purpose gateway

Sources

• Business Process Management (ULB)