[rules-dev] Fine Grained Property Change Listeners (Slot Specific)

[Wolfgang Laun]

You really should follow naming conventions Java programmers are familiar
with. javax.xml.bind.annotation.XmlAccessType, for instance, uses the
term "member" for referring to "public getter/setter pairs", and this comes
close to what Drools does. Alternatively, there's "field" and "property",
and I wouldn't worry about the extra lip mileage - you can always abbreviate
to "prop-specific".

Is this new feature in some way configurable for the KnowledgeBase?
There are fact types where modifying one member results in the change
of more than one member. Consider the very plausible case:
     $f: Fact(...)
   then
      modify( $f ){ getList().add( $x ) }
   end

   when
     Fact( size > 10 )  # size implemented as getList().size()
   then

Wolfgang

PS: The new feature is actually *restricting the sensitivity of the system.*
Therefore, I feel that "high-fidelity" is actually counter-intuitive!


On 13 January 2012 23:30, Mark Proctor <mproctor at codehaus.org> wrote:

> Mario just got a first cut working for fine grained property change
> listeners. Previously when you call update() it will trigger revaluation
> of all Patterns of the matching object type in the knowledeg base.
>
> As some have found this can be a problem, forcing you to split up your
> objects into smaller 1 to 1 objects, to avoid unwanted evaluation of
> objects - i.e. recursion or excessive evaluation problems.
>
> The new approach now means the pattern's will only react to fields
> constrained or bound inside of the pattern. This will help with
> performance and recursion and avoid artificial object splitting.  We
> previously discussed this here:
> http://blog.athico.com/2010/07/slot-specific-and-refraction.html
> You can see the unit test here:
>
> https://github.com/droolsjbpm/drools/blob/ca55c78429cbc0f14167c604c413cdc3faaf6988/drools-compiler/src/test/java/org/drools/integrationtests/MiscTest.java
>
> The implementation is bit mask based, so very efficient. When the engine
> executes a modify statement it uses a bit mask of fields being changed,
> the pattern will only respond if it has an overlapping bit mask. This
> does not work for update(), and is one of the reason why we promote
> modify() as it encapsulates the field changes within the statement. You
> can follow Mario's chain of work on this at his github activity feed:
> https://github.com/mariofusco.atom
>
> The adventerous amoung you can pick this up from hudson, or from maven,
> and start playing now. My hope is that this will make drools much easier
> to use:
>
> https://hudson.jboss.org/hudson/job/drools/lastSuccessfulBuild/artifact/drools-distribution/target/
>
> Btw we are after a name. Drools is not a frame based system, so "slot
> specific" doesn't seem appropropriate. Property Specific seems a bit of
> a mouth full. I'm quite liking High Fidelity Change Listeners :) any
> other suggestions?
>
> slot-specific is the name used by Jess for this feature,
> http://www.jessrules.com/docs/71/constructs.html. It's also the standard
> way that Clips COOL works, which is the Clips OO module. Although that's
> partly a side effect of the triple representation of properties used in
> COOL, and the modifications are triple based. I don't know what
> mechanism Jess is using to enable this.
>
> Mark
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