Process Is The Main Thing

@ Anatoly Belaychuk’s BPM Blog

BPMN Signal Start

A short addendum to previous post “A Case For BPMN Signal Event“.

The pecularity of the signal event noted there - a signal is catched by every instance of a receiver process which is waiting for the event at the moment the signal is thrown - refers to intermediate events.

In case of start event one process initiates a signal and another process starts as a result. But why using a signal here - a message seemingly can do the same?

Firstly, a signal allows to initiate several processes at once.

Secondly, a signal has conceptual advantage:

  • Let a given signal thrown by a process A initiate start of a process B.
  • Now let’s recall that BPM is a management of business processes that change in time and assume that we decided to make process C handle the signal instead of B.
  • When a message is used, the receiver is specified in process A, hence we need to modify A scheme in order to change the handler. And if we do we got a problem with A instances already running.
  • When a signal is used, we simply install C and uninstall B. We don’t need to modify A nor to do anything with A instances.

This way signal implements late binding: a handler can be set/reset at time of execution rather than development.

09/13/10 | Articles | , , ,    

Comments (3)

  1. David French 09/13/10 11:05 PM

    It allows the ultimate “late binding” of not having to design the world process … only the bit you are in control of at the moment. When you come to an event that you know will be useful to another bit of the enterprise … Signal … then when a use is found in another bit of process design you do not have to redo the process design work again. Of course, you will need a way to hunt down these useful signals and some standardisation of how they will look in your enterprise.
    Yes, I know that the end-end process is sacrosanct but the real world is better with some compartmentalising … a bit like the IT world of programming.

  2. Anatoly Belychook 09/14/10 02:31 PM


    Regarding end-to-end processes: it’d be too simple if they could be implemented by a single-threaded diagram. It’s an extremly vulgar view.

    I’m going to get back to this topic because for me it’s the coolest thing in BPM and BPMN.


  3. Scott 10/04/10 10:25 PM

    Interesting writeup. This is, incidentally, how one BPM product always treated events (since 2004/5) - e.g. late binding of them to process starts and Intermediate messages across any number of instances. Its a very useful abstraction.

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