[rules-users] Help needed - Problems with forall operator

[Tom.E.Murphy at wellsfargo.com]

Thanks, everyone, for your insightful responses. You've made my day...

Tom Murphy
Business Process Consultant
Wells Fargo HCFG - CORE Deal Decisioning Platform
800 S. Jordan Creek Parkway | West Des Moines, IA 50266
MAC: X2301-01B
Office: 515 324 4853 | Mobile: 941 320 8014
This message may contain confidential and/or privileged information.  If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein.  If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message.  Thank you for your cooperation.

----------------------------------------------------------------------

Message: 1
Date: Sat, 7 Nov 2009 09:55:37 +0100
From: Wolfgang Laun <wolfgang.laun at gmail.com>
Subject: Re: [rules-users] Help needed - Problems with forall operator
To: Rules Users List <rules-users at lists.jboss.org>,
	ed.tirelli at gmail.com
Message-ID:
	<17de7ee80911070055k2469051agfebf3a5be24c7165 at mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

Here's the explanation why Tom's version does not work. The first pattern of
a "forall" defines the domain, which is: all CreditReport facts; for each
object in this domain, the remaining patterns must match; since the FICO
pattern merely ascertains the existence of a single FICO chained to a parent
CreditReport with validScoreIndicator false, it fires as soon as there is
one for each of the existing CreditReports.

Jared's solution has the CreditReport CE in front of the forall, unadorned
with any quantifier, and the innate behavior of Drools makes sure that the
hole thing will be tried, once, for any existing CreditReport anyway. Then,
the forall domain is now FICOs with that CR's id and valid == false - but
what is the CE? I guess that Drool's behavior is somewhat off the
definition, using just FICO() - i.e., all existing FICO objects - as the
domain. (However, I think that Edson changed this recently for 5.1.0.) Thus,
Jared's rule indeed fires only when all FICOs are linked to the CreditReport
are false, but it fails to do so as soon as there is at least one other FICO
with either a different parent, or valid.

Therefore, to be on the safe side with multiple CreditReport facts and
assorted FICO's being in WM at the same time, I propose this rule:

rule "somerule2"
when
    report: CreditReport( $parentCreditReport_1_Id : myId)
    forall ( $f : FICO( parentId == $parentCreditReport_1_Id )
             FICO( this == $f, validScoreIndicator == false) )
then
    System.out.println("somerule2 fired on " + $parentCreditReport_1_Id );
end

Here, the domain is explicitly given as all FICOs of the current CR; and for
all of them valid must be false.

Still, this solution is not perfect: It would also fire in the absence of
any FICO for some CR. To fix this, add a guard against there being no FICOs
for the current CR:

report: CreditReport( $parentCreditReport_1_Id : myId)
            exists FICO( parentId == $parentCreditReport_1_Id )
forall ( $f : FICO( parentId == $parentCreditReport_1_Id )
             FICO( this == $f, validScoreIndicator == false) )

To complete the picture, one might equally well use the negation of forall,
which would have to be propagated into the predicate (read '|' as "so
that"):
    forall x in D | P(x) => not existst x in D | not P(x)

Now the condition delimiting the domain and the negated predicate can be
merged again into one CE:

rule "somerule3"
when
    report: CreditReport( $parentCreditReport_1_Id : myId)
    exists FiCo( parentId == $parentCreditReport_1_Id )
    not ( exists FiCo( parentId == $parentCreditReport_1_Id, validScore ==
true) )
then
    System.out.println("somerule3 fired on " + $parentCreditReport_1_Id );
end

-W

On Fri, Nov 6, 2009 at 9:45 PM, Jared Davis <sunray at davisprogramming.com>wrote:

> I think this usage may work for your case.
>
> rule "somerule"
>  when
>    report: CreditReport( $parentCreditReport_1_Id : myId)
>    forall (
>       FICO( parentId == $parentCreditReport_1_Id, validScoreIndicator ==
> false)
>    )
>  then
>     System.out.print("Fired on " + $parentCreditReport_1_Id );
> end
>
>
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-users/attachments/20091107/9bc576d5/attachment-0001.html