[rules-users] Implementing Refraction with Drools

[Mark Proctor]

You can improve your example by using an agenda listener to remove Activations once they are cancelled, this way you avoid a memory leak.

Further you can use annotations, to control this per rule.
rule xxx @repeatable(true) when
then end

then in your filter you can check rule.getMetaData( "repeatable" )

We aren't going to add this to Drools right now, but it certainly is a useful example for people. 

We'll be reviewing execution control during the 6.x series, and we'll look at it then. I believe that you can have different types of repeability, and I'd like to look at rising falling edges. It's important that you don't add features one at a time, as one might make another impossible.  So these things must be look at, as a whole, and planned out.

Mark
On 23 Jan 2013, at 00:39, magaram <magaram at deltadentalmi.com> wrote:

> Thanks for the clarifications Mark and Wolfgang. I wanted to share some
> additional data.
> I was trying to reproduce the same behavior that ILOG JRules exhibits by
> default for refraction.
> 
> My experiment with no-loop and lock-on-active did not work when I compared
> against my baseline results with JRules. However, the interesting part was
> when I ratified the agenda filter as follows (wrong and hacky as it is) -
> removed the encounteredActivations.remove(act) before returning false, it
> matched the ILOG baselines exactly. I ran through 46 test cases as part of
> my baseline, all of which have several looping opportunities single and
> complex. My earlier agenda filter implementation that I posted earlier did
> not yield identical results with the JRules baseline.
> 
> It seems this logic for refraction seems to mimic JRules refraction
> behavior.  From commercial use case perspective refraction/repeatability
> control is important. ILOG implements refraction out of the box as part of
> conflict resolution. However they offer up a antecedent directive called
> refresh (in lieu of update) that overrides refraction...
> 
> import java.util.ArrayList;
> import java.util.List;
> 
> import org.drools.runtime.rule.Activation;
> import org.drools.runtime.rule.AgendaFilter;
> 
> /**
> * This custom agenda filter injects refraction behavior into the rule
> engine
> * @author Mukundan Agaram
> *
> */
> public class RefractionAgendaFilter implements AgendaFilter {
> 	private List<Activation> encounteredActivations = new
> ArrayList<Activation>();
> 
> 	@Override
> 	public boolean accept(Activation act) 
> 	{
> 		//Check for a Refraction
> 		if (encounteredActivations.contains(act))
> 		{
> 			return false;
> 		}
> 		//Otherwise add the rule to check for potential refractions in the future
> 		encounteredActivations.add(act);
> 		//select the rule to be part of the agenda
> 		return true;
> 	}
> 
> }
> 
> 
> 
> 
> --
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