11 September 2013

Process Patterns (Part 1) - Basic Patterns

This is Part 1 of a series of articles introducing the common process patterns depicted using BPMN 2.0 elements. The series will covers the various workflow patterns based on the Workflow Patterns research paper by Aalst, Hofstede, Kiepuszewski and Barros. The first part looks at the five basic process patterns.

Basic Process Patterns

The five Basic Control Flow Patterns are the elementary aspects of process control and similar to the concepts originally proposed by the Workflow Management Coalition (WfMC). Most BPMSs and process modelling tools provide these basic patterns as process templates.

The five basic process patterns are:
  1. Sequence
  2. Parallel Split
  3. Synchronization
  4. Exclusive Choice
  5. Single Merge


Pattern 1 Sequence

Description
An activity in a process in enabled after the completion of a preceding activity in the same process.
Key BPMN 2.0 Elements
  • Task
BPMN 2.0 Process Diagram

Examples for Business Application
  • Verify account activity is performed after capture credit card details activity.
  • Send invoice activity is performed after deliver order activity.


Pattern 2 Parallel Split

Description
The divergence of a control flow into two or more control flows which the flows are executed concurrently, thus allowing the activities in the different flow to be executed simultaneously.
Key BPMN 2.0 Elements
  • Task
  • Parallel gateway
BPMN 2.0 Diagram

Examples for Business Application
  • Receive payment activity enables two parallel activities Ship order and Notify customer.
  • Receive intrusion alarm activity triggers both despatch patrol activity and inform police activity.


Pattern 3 Synchronization

Description
The convergence of multiple parallel activities into one control flow such that the control flow is passed to the subsequent activity when all incoming flows have been enabled. Assumption: Each incoming flow is executed only once in a process instance.
Key BPMN 2.0 Elements
  • Task
  • Parallel gateway
BPMN 2.0 Diagram

Example for Business Application
  • Evaluate insurance claims activity is triggered after both check policy activity and Assess damage activity are performed (in parallel) and completed.


Pattern 4 Exclusive Choice

Description
The control flow splits into two or more flows, the control is immediately passed to precisely one of the outgoing flows based on a mechanism that can select one of the outgoing flows. The mechanism can be a decision from previous activity such as a business rule task or based on process data of the process instance.
Key BPMN 2.0 Elements
  • Task
  • Exclusive gateway
BPMN 2.0 Diagram

Examples for Business Application
  • Determine claim type activity is followed either by evaluate simple claim activity or evaluate complex claim activity.
  • After count vote activity is completed, either declare results activity or allocate reference votes activity is undertaken.

Pattern 5 Single Merge

Description
The convergence of two or more alternative activities into one control flow such that the control flow is passed to the subsequent activity when one incoming flow have been enabled. Assumption: The incoming alternative flows will ot ever be executed in parallel in a process instance.
Key BPMN 2.0 Elements
  • Task
  • Exclusive gateway
BPMN 2.0 Diagram
Examples for Business Application
  • After either receive payment activity or approve credit activity, delivery order activity is undertaken.
  • Archive claim activity is performed after either pay claim activity or reject claim activity.




What's next

Coming up in the next article Advanced Branching and Synchronization Process Patterns using BPMN 2.0.

References

  1. W.M.P. van der Aalst, A.H.M. ter Hofstede, B. Kiepuszewski and A.P. Barros. (2003) Workflow Patterns
  2. N. Russell, A.H.M. ter Hofstede, W.M.P. van der Aalst, and N. Mulyar. (2006) Workflow Control-Flow Patterns: A Revised View. BPM Center Report BPM-06-22, BPMcenter.org