[rules-users] Run a set of rules in a group B from a rule in agroup A

[Edson Tirelli]

    Michael is right. It is just harder to explain than to do it. Just take
a look at agenda-groups or ruleflow-groups. Chose which one you prefer to
use it, place your rules in two separate groups: A and B.

    If using agenda-groups, set initial focus to A, fireAllRules and make
sure that on the consequence of one of the rules from group A you set focus
to B. So if that rule never fires, B will never have the focus and will
never fire. Just remeber that agenda-groups work like a stack, so if you
want ALL rules from A to execute before B, add the setFocus on the rule with
the lowest salience in A.

    Using ruleflow-groups is similar, but you draw your "flow" graphically,
and it does not work like a stack. Sometimes easier for your use case.

    []s
    Edson

2009/1/21 Anstis, Michael (M.) <manstis1 at ford.com>

> Hi,
>
> See below.
>
> "executing a rule" is really two parts: LHS pattern matching (which
> can't be stopped for a given RuleBase) and execution of the RHS (which
> can be controlled by the agenda and truth maintenance).
>
> I hope my time away hasn't led to me giving wrong advice.
>
> Mike
>
> -----Original Message-----
> From: rules-users-bounces at lists.jboss.org
> [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Thierry B
> Sent: 21 January 2009 12:53
> To: rules-users at lists.jboss.org
> Subject: RE: [rules-users] Run a set of rules in a group B from a rule
> in agroup A
>
>
> Hello,
>
> So if I've well understand :
>
> - before calling fireAllRules(), Drools know for all rules (from any
> group)
> definied in DRL files, those which all patterns in the LHS of a rule are
> matched, and those rules are placed on a agenda.
>
> At which moment exactly, Drools verified from a rule that all of its
> pattern
> in the LHS are matched, if it's before callling fireAllRules() ?
>
> >>> Yes, LHS is evaluated on workingMemory.insert(o). A call to
> fireAllRules() executes the activations on the agenda (i.e. RHS queued
> as a consequence of LHS being matched on workingMemory.insert(o)).
>
> - And fireAllRules() permit to execute all rules that are placed on
> agenda
>
> >>> Yes
>
> - When using setFocus() from a java class or a rule, we can control the
> order of rules to specify to execute rules from group B, and group C...
>
> >> I believe so.
>
> - So it's not possible to tell Drools that we don't want to execute a
> group
> of rules if a rule A is not matched : in that group of rules : those
> which
> all paterns match LHS will be inevitably executed.
>
> >>> Wrong. The rules won't be executed (read as activations - RHS -
> won't be run) but you can't stop the LHS being evaluated.
>
> All these points that I said, are exact?
>
> Thanks :-)
>
>
> Anstis, Michael (M.) wrote:
> >
> > Please accept that my knowledge is based on 4.x and there might be
> other
> > alternatives in 5.
> >
> > Rules are not "ran" but their patterns (LHS) evaluated as facts
> > (objects) are inserted into Working Memory. When all patterns in the
> LHS
> > of a rule are matched activations are placed on the agenda for
> execution
> > of the consequence (RHS) when fireAllRules() is called (or other
> > mechanisms to run what is on the agenda are invoked; such as
> RuleFlow).
> > So you could have rules in Group A cause Group B to receive the focus
> > but it is the RHS's execution order you control and not the pattern
> > matching - which will happen for Group A and Group B when facts are
> > inserted into WM.
> >
> > Look at Agenda Groups and RuleFlow. This should help.
> >
> > With kind regards,
> >
> > Mike
> >
> >
>
> --
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>
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-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss, a division of Red Hat @ www.jboss.com
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