2012-09-02

Practical process anti-pattern: DOUM

Avoid the "DOUble Master" (DOUM) anti-pattern (section 5.6 of my book "Improving enterprise BPM systems")

As coordination can be carried out by an application or by a process engine, we have to be very careful to avoid the “double master” anti-pattern. At any moment in time there must be only one master responsible for the coordination of a particular process instance. (Of course, the coordination role may be delegated if appropriate.) This is analogous to a well-organised meeting where the chairperson decides who talks next.
Also well-coordinated work improves the security and integrity of data. It can be a useful design pattern to consider that only the person who has accepted a particular human activity can modify the business objects associated with that human activity. This is a dynamic granting/revoking of permissions which is synchronised with the process. Something like in the diagram below (which is not a valid BPMN as there are no "claim" and "unclaim" events defined).



The non-recognition of this anti-pattern can be very costly. We have observed a BPM solution which allowed the modification of data by a process engine, by an interactive application (i.e. by a human) and by a batch at the same time. The coordination of activities was based on data and, if necessary, the application or the batch could “correct” the process. The process engine was used mainly for the handling of three human activities, and the implementation of this solution (for a relatively simple business process) took several man-years.

Thanks,
AS
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