[rules-users] Anti-rules and infinate loops

[Myles Goodhue]

Hello,

I have a set of rules that determine a target date for a business object 
based on which rule criteria the object matches.  When the business 
object is asserted, the target date field may or may not be null.  My 
problem is if the business object does not match any of the rules I 
would like the target date set to null and since there are multiple rule 
possibly affecting the same object I would rather not create an 
"anti-rule" for each rule which sets the target date to null.

I've tried creating a rule with a higher salience value which sets the 
target date to null, if it is not already, and modifies the object but 
when the object matches another rule and modifies the object again it 
goes into an infinite loop.  I could probably set the target date to 
null before asserting it into the rule engine but I was hoping to keep 
it self contained.

Here's an example of what I'm talking about:

rule "Pre"
   salience 10
   no-loop true
   when
      $bo : MyObject( targetDate != null )
   then
      Date tmp = null;
      $bo.setTargetDate(tmp);
      modify($bo);
end

rule "Post a"
   no-loop true
   when
      $bo : MyObject( targetDate == null, criteriaMatches == "A")
      $someDate : ThisDateObject();
   then
      $bo.setTargetDate($someDate);
      modify($bo);
end

rule "Post b"
   no-loop true
   when
      $bo : MyObject( targetDate == null, criteriaMatches == "B" )
      $someDate : ThatDateObject();
   then
      $bo.setTargetDate($someDate);
      modify($bo);
end

etc...

I'm pretty sure there is a simple answer but it just won't come to me.  
Thanks for any help.

Myles

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CGI ISMC - DynaDocs

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