By Rashid N. Khan
Junction steps in a business process are dummy steps since they're constructs to denote steps in a process that don't represent any task. Even though they don't represent any tasks, they can be useful when developing sophisticated business processes. The four major benefits of junction steps are that they can be used to implement process joins, splits, conditions and iterations. This month's "Practical BPM" column describes each type of junction step and shows examples.
Joins
In many process designs it's often necessary to join a number of parallel process paths into a single path. This can always be accomplished by using an ordinary user step at the junction point. However, doing so will invoke a user task. If the steps immediately after the join are to be determined based on a condition, it's impractical to use a user step for this purpose. Consider the process in Figure 1 as an example.
| Figure 1: Using junction steps for joins. |
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This process has three paths that converge into a single path. When the three paths are joined, the process needs to activate the Approval step if the amount is less than $1,000 and the Manager step if the amount is more than $1,000. Such a process can't be designed simply by placing a user step at the junction point. This is a good example where a junction step can be used as a process join. The Approval and Manager steps are immediately following the junction steps and can be invoked based on any conditions.
Splits
Splits are the reverse of joins. In many cases it's necessary to split a single process path into a number of parallel paths. Junction steps can be used to implement such splits as shown in Figure 2. Again, while a user step could also be used to implement a split, the ability to use a junction step provides additional flexibility that doesn't require a user step.
| Figure 2: Using junction steps for splits. |
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To illustrate the power of using junction steps for joins and splits, consider the process illustrated in Figure 3.
| Figure 3: A process map without splits and joins. |
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When any of the steps A, B or C are completed, it's desired that steps P, Q, R and T be invoked. Since any of the first three steps can invoke the latter four steps, the resulting process map represents spaghetti if we don't have junction steps. However, by using junction steps as shown in Figure 4, the three parallel paths from step A, B, C and D can be joined by the junction steps and then split to the four paths represented by steps P, Q, R and T.
| Figure 4: A process map simplified by splits and joins. |
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Conditions and Actions
Some advanced BPM solutions allow junction steps to have conditions and actions. This means that a junction step can be invoked on a conditional basis. Furthermore, when a junction step has been executed, it can invoke other actions on a conditional basis. The ability to invoke other actions from within a junction step on a conditional basis provides the capability to implement complex logic and actions through the intelligent use of junction steps.
Iterations
In many process design situations it's necessary to invoke a collection of steps on a conditional basis. When these steps have finished, it's necessary to return to the point from where the collection of steps was invoked and proceed from there. Junction steps provide a good mechanism of implementing iteration as shown in Figure 5. Here the steps to be called on an iterative basis from various points in the main process are preceded by junction steps, then followed by another. Conditional logic within the junction steps controls the iterations in the step. When the iteration is complete, control returns to the main process thread.
| Figure 5: Using junctions for iterations. |
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Since junction steps don't involve any tasks, they don't have recipients or completion times associated with them. However they may have "delay time" as a property, allowing these steps to be synchronized with other events similar to user steps and application steps.
Useful Links
This article is an excerpt from Rashid Khan's Business Process Management: A Practical Guide. Order your copy here:
http://www.bpmenterprise.com/yDQ
Ultimus
http://www.ultimus.com
Rashid N. Khan is the founder and Chief Technical and Strategy Officer of Ultimus Inc., a pioneer in business process management and workflow automation. Prior to establishing Ultimus, founded Sintech Inc., a leader in advanced software for mechanical testing. Rashid sold Sintech to MTS Systems in 1989, where he worked for a five years as a vice president and general manager. During this period he took the company through ISO 9000 certification. This experience made him aware of the need for business process management and workflow automation. Rashid obtained two undergraduate degrees from MIT in computer science and political science. Khan is the author of Business Process Management: A Practical Guide, has published numerous articles and spoken at a number of events. Contact Rashid N. Khan at info (at) ultimus.com or visit http://www.ultimus.com.
