Workflow Patterns in Workflow Nets
Sequence
First task $a$, then task $b$
Parallel Split
Tasks $b$ and $c$ are processed in parallel
- this construction is also called “AND-split”
Synchronization
Do $d$ only after both $b$ and $c$ are completed
- this is a synchronization between two parallel processes
- this construction is also called “AND-join”
Parallel Routing
A combination of Parallel Split and Synchronization
Exclusive Choice
after $a$, do $b$ or $c$
- choice in this case depends on the results of the activity $a$
- here both ‘'’doA’’’ and ‘'’doB’’’ will be active, but we want to fire only one of them, based on the activity $a$
Simple Merge
perform $d$ after $b$ or $c$ finishes
Alternative Routing
a combination of Exclusive Choice and Simple Merge
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