[rules-users] How to track constraint truth [was: Non short circuit ANDing]

[Wolfgang Laun]

ad 4) I would not generate the final processing since there are too many
possible variations. One might use it as I've shown, but there might
also be an opportunity to use some sort of accumulate of Collectors of
a kind into a list, and you just don't know what to put into the
consequence.

ad PS) I have one Monitor implements AgendaEventListener with a constructor
   Monitor( KnowledgeRuntime kRuntime )
that sets itself as a
   global Monitor monitor
so that the extended rules can call the Collector method
   addFiring( monitor.getRulename() )
so that an evaluation rule can retrieve the names of the rules that have fired.

-W


On 03/02/2013, Cotton, Ben <Ben.Cotton at morganstanley.com> wrote:
> Nice.  Very straight forward too.
>
>
>
> To summarize my understanding:
>
>
>
> Given an initial "business rule"  all that has to be done is to implement a
> Fluent Builder tool that generates the business rule re-write as
>
>
>
> 1.   an initial root rule (e.g. "car"), that when fired activates a
> "Collector"
>
>
>
> 2.   a set of n extended rules (1 for each L-Value predicate participant in
> the original business rule)
>
>
>
> 3.   whenever rule i (of the  n extended rules) matches, rule i does
> Collector booking in its RHS consequence processing. (accounting for
> predicate participant i)
>
>
>
> 4.  generate a final set of rules that match on the Collector's account of
> success/failure and reports on any specific details of that accounting in
> these final set of rules' callback(s) to the Collector implementation (e.g.
> your RHS invoke of Collector.missing() to render "price > 1000" as point of
> failure)
>
>
>
> I think I get it, starting to exercise this now.
>
>
>
> THANKS WOLFGANG!
>
>
>
> P.S.  Wolfgang, do you have any comment wrt to using WM Listener(s) and
> their event callback processing (in conjunction w/ this pattern) as an
> effective tactic for helping to account/audit for when rules fail to fire?
>
>
>
>
>
> -----Original Message-----
> From: rules-users-bounces at lists.jboss.org
> [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Wolfgang Laun
> Sent: Saturday, February 02, 2013 5:26 AM
> To: Rules Users List
> Subject: [rules-users] How to track constraint truth [was: Non short circuit
> ANDing]
>
>
>
> To summarize the discussion of the major part of the cited thread:
>
>    * There are situations when it is of interest to learn which of the
> several constraints of a rule are true and which block it from firing.
>
>    * It is known that manually writing a set cooperating rules can solve
> this problem (e.g., Rule Design Pattern "Learning the Reason for
>
> Failure")
>
>    * Some automatism supporting the creation of such a set would help
>
>
>
> Considering such a support, one wonders which level of complexity in the
> primary rule it must be able to handle. The task in itself procures a
> limitation, e.g., when one pattern must match so that a binding is available
> which is used in a successive pattern. (More
>
> formally: the dependency graph of bindings restricts the investigation of
> the truth of LHS sub-terms.) Furthermore, any solution using
> reverse-engineering from the internal representation of a LHS isn't simple,
> and the API for accessing a compiled rule isn't "stable".
>
>
>
> But I think that simple scenarios can be handled by a simple rule authoring
> tool. I'll explain this by using an example: a rule investigating offered
> cars according to a buyer's wishes:
>
> class Car {
>
>    String colour;
>
>    int price;
>
>    int horsepower;
>
>    boolean abs;
>
> }
>
>
>
> rule "car"
>
> when
>
>    $car: Car( colour == "red", price < 1000, horsepower >= 150, abs == true
> ) then ... end
>
>
>
> To permit the individual investigation of constraints, this might be
> rewritten as:
>
>
>
> rule "car"
>
> when
>
>    $car: Car()
>
> then end
>
>
>
> rule "car colour == \"red\"" extends "car"
>
> when
>
>   Car( this == car, colour == "red" )
>
> then // Gosh, a red one!
>
> end
>
>
>
> rule "car price < 1000" extends "car"
>
> when
>
>   Car( this == car, price < 1000 )
>
> then // Hey, it's cheap enough!
>
> end
>
>
>
> And so on. - For a fully automatic process, a "Collector" fact has to be
> maintained for each fact (or Cartesian product of facts) matching the
> initial rule (i.e., "car"). Into this Collector, positive results from the
> extending rules are injected, so that, ultimately, it can be examined for
> full information. Here's a couple of examples of rules doing just that, with
> the rule id and failure count as positional
>
> properties:
>
>
>
> rule "success"
>
> when
>
>     $c: Collector( "car", 0; )
>
> then
>
>     System.out.println( "Found the car I want: " + $c.get( "car" ) ); end
>
>
>
> rule "almost"
>
> when
>
>     $c: Collector( "car", 1; )
>
> then
>
>     System.out.println( "Almost the car I want: " + $c.get( "car" ) );
>
>     $c.missing();
>
> end
>
>
>
> Given the Car( "red", 1200, 160, true ), the second rule fires and
> produces:
>
>
>
> Almost found the car I want: Car [colour=red, price=1200, horsepower=160,
> abs=true]
>
> missed: price < 1000 in Car
>
>
>
> How to write the original rule is the last point. The actual user interface
> could be simpler, but here is a basic fluent API:
>
>
>
> public String makeRuleText(){
>
>     RuleSet ruleSet = new RuleSet( "com.sample", "car" )
>
>     .add(new BasicPattern( "car", Car.class ) )
>
>     .add( new Constraint( "colour == \"red\"" ) )
>
>     .add( new Constraint( "price < 1000" ) )
>
>     .add( new Constraint( "horsepower >= 150") )
>
>     .add( new Constraint( "abs == true" ) );
>
>     return ruleSet.toString();
>
> }
>
>
>
> Cheers
>
> Wolfgang
>
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>
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