[rules-users] Ruleflow "OR" Split Nodes

[Kris Verlaenen]

Hans,

The behaviour you are witnessing is indeed expected behaviour.  The problem is that we currently do not have a matching OR-join construct, so it is indeed difficult to model behaviour like you want to.  The reason is that is it a very difficult problem to create a generic OR join, i.e. a join that waits until all incoming connections either have been completed or were not triggered.  In the example you are using it would still be pretty straighforward, however it becomes very difficult if you take random splitting and joining after the or-join into account, incomplete or joins and even unstructured looping.

I will add a n-of-m join type, meaning the join will wait until n of its incoming connections has been triggered.  Since this n could be read from a variable, it allows you to do any kind of complex joining, but the process designer should make sure to update the n variable itself so it matches the correct number of incoming connections to wait for.

An alternative would be to provide matching OR-split - OR-join constructs, as those aren't difficult to support either, but not quite as powerful (we do implement this in our BPEL prototype but there it is much easier as BPEL is a structured process language).

You could also replace your OR construct by an XOR followed by AND splits, but that would probably make the process a lot more difficult to read.

Kris

  ----- Original Message ----- 
  From: ringsah at comcast.net 
  To: rules-users at lists.jboss.org 
  Sent: Wednesday, November 19, 2008 3:59 PM
  Subject: [rules-users] Ruleflow "OR" Split Nodes


  I am having a problem with the ruleflow in Drools 4.0.7. I have the following simple ruleflow with a split node with a type of "OR" with two outgoing connections, each going to a different ruleflow group (image of ruleflow attached).



  The problem I am having is with the join node, into which the two ruleflow groups connect back in. If I use a join node type of "AND", then it works okay unless only one branch is executed. Then the action, which simply prints "Action node" to the console, never gets executed.

  If I use a join node type of "XOR", then it works okay unless both branches are executed. Then it appears that both branches are executed, because the action get executed twice. However, the rules from the ruleflow group in only one of the branches end up getting fired.

  I have attached a zip file containing an extremely simple eclipse test project that illustrates the problem.

  Thanks in Advance,
  -Hans





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