[rules-users] Grouping rules
Edson Tirelli
tirelli at post.com
Wed Feb 6 08:29:43 EST 2008
The answer is not simple. :)
All the alpha constraints are evaluated at fact assertion time, does not
matter if they are early or late in the pattern order. Although, alpha
constraints are usually quite cheap, since they are constraints that do not
depend on other facts. Example:
Person( name == 'bob' )
"name == 'bob'" is a literal constraint and do not depend on any other
pattern (so it is an alpha constraint) and will be evaluated at assert time,
does not matter the order in which patterns are written down.
Beta constraints are constraints that depend on previous patterns and
will only be evaluated when previous patterns are matched. Example:
when
Person( $likes : likes )
Cheese( type == $likes )
then
end
It is obvious in the previous example that "type == $likes" depends on
the value of $likes that is a variable bound in a previous pattern (so it is
a Beta constraint). It will only be evaluated if ALL previous patterns
match.
"from" CE is a special case of beta "node", that is only evaluated when
all previous patterns match.
[]s
Edson
2008/2/6, Anstis, Michael (M.) <manstis1 at ford.com>:
>
> Great news!
>
> Is this specific to the use of "from" whereas another rule like:-
>
> rule "avoid expense"
> when
> ControlFact( phase == "do expensive call" )
> AnotherFact( someExpensiveTimeConstantFunctionCall == someValue )
> then
> // Do something
> end
>
> Could not have the LHS not evaluated or (to avoid a double negative),
> would always have the LHS fully evaluated ;-)
>
> ------------------------------
> *From:* rules-users-bounces at lists.jboss.org [mailto:
> rules-users-bounces at lists.jboss.org] *On Behalf Of *Edson Tirelli
> *Sent:* 06 February 2008 12:29
> *To:* Rules Users List
> *Subject:* Re: [rules-users] Grouping rules
>
>
> Yes, it is possible to prevent the evaluation of part of the LHS
> patterns by the use of previous constraints and/or the introduction of
> control facts.
>
> For instance:
>
> rule "avoid expense"
> when
> ControlFact( phase == "do expensive call" )
> AnotherFact( ) from someExpensiveServiceCall
> then
> // Do something
> end
>
> In the above example, the "someExpensiveServiceCall" will only be
> executed when the previous patterns are matched, i.e., when phase
> attribute of the ControlFact has the value "do expensive call".
>
> []s
> Edson
>
> 2008/2/6, Anstis, Michael (M.) <manstis1 at ford.com>:
> >
> > I'm not sure as LHS's are evaluated when facts are inserted not when
> > fireAllRules (or execute) is called.
> >
> > You can prevent the RHS from activating by using (for lack of a better
> > name) "flag facts" (but this doesn't solve your problem); for example:-
> >
> > rule "avoid expense"
> > when
> > not exists Flag()
> > AnotherFact( ) from someExpensiveServiceCall
> > then
> > // Do something
> > end
> >
> > Don't forget though that if you share LHS patterns across multiple rules
> > they will share the same nodes in the RETE network, so although you might be
> > aware that the expensive calls are not required for some rules they might be
> > required for other rules and hence you'll need to perform the expensive call
> > when the facts are inserted in order for the other rules to activate.
> > Perhaps if you better describe your use-case there might be a better
> > solution.
> >
> > With kind regards,
> >
> > Mike
> >
> > ------------------------------
> > *From:* rules-users-bounces at lists.jboss.org [mailto:
> > rules-users-bounces at lists.jboss.org] *On Behalf Of *Jai Vasanth
> > *Sent:* 05 February 2008 19:35
> > *To:* Rules Users List
> > *Subject:* Re: [rules-users] Grouping rules
> >
> > I had another question on these lines. Is there a way to preven even
> > the LHS from evaluating for certain cases ? A few of my LHS computation
> > involve some expensive service calls and I would like to avoid unless and
> > until it is asolutely necessary.
> >
> > Thanks
> >
> > Jai
> >
> > On Feb 1, 2008 8:35 AM, Jai Vasanth <jaivasanth at gmail.com> wrote:
> >
> > > Thanks. That helped.
> > >
> > >
> > > On Feb 1, 2008 7:31 AM, Anstis, Michael (M.) <manstis1 at ford.com>
> > > wrote:
> > >
> > > > Excuse me if you already understand but there is a difference
> > > > between rule patterns being evaluated and their consequence running.
> > > >
> > > > Rules LHS are evaluated when objects are inserted into working
> > > > memory whereas the consequence fires when you call fireAllRules();
> > > >
> > > > The rules whose activations are executed are those in the given
> > > > Agenda Group; thereafter those not in any agenda group execute. So if all
> > > > rules are in an Agenda Group you should be OK.
> > > >
> > > > Of course they don't prevent all rule patterns from being checked as
> > > > objects are inserted into WM (which has a performance impact) but this is
> > > > what the RETE network was designed to optimise.
> > > >
> > > > You could try another configuration (but I think Agenda Groups are
> > > > probably the preference by design). This gives complete isolation - but I
> > > > haven't tried it so it might not even be possible ;-)
> > > >
> > > > global WorkingMemory wm;
> > > > global RuleBase rbX;
> > > > global RuleBase rbY;
> > > >
> > > > rule "Group X"
> > > > when
> > > > Fact( attribute == "condition1" )
> > > > then
> > > > wm = rbX.newStatefulSession();
> > > > wm.fireAllRules();
> > > > end
> > > >
> > > > rule "Group Y"
> > > > when
> > > > Fact( attribute == "condition2" )
> > > > then
> > > > wm = rbY.newStatefulSession();
> > > > wm.fireAllRules();
> > > > end
> > > >
> > > > Good luck.
> > > >
> > > > Mike
> > > >
> > > > ------------------------------
> > > > *From:* rules-users-bounces at lists.jboss.org [mailto:
> > > > rules-users-bounces at lists.jboss.org] *On Behalf Of *Jai Vasanth
> > > > *Sent:* 01 February 2008 15:07
> > > > *To:* Rules Users List
> > > > *Subject:* Re: [rules-users] Grouping rules
> > > >
> > > >
> > > > Thanks for responding
> > > > Yes, I did consider agenda groups, but I thought agenda groups only
> > > > ordered execution in a particular fashion, so if Rule "pick group X" fires
> > > > then it would make sure that rules in Agenda Group X fire first before the
> > > > remaining but the remaining would fire eventually. Is my understanding
> > > > correct ?
> > > > I am looking for a solution for completely isolating a rule set
> > > > conditioned on an object attribute.
> > > >
> > > > On Feb 1, 2008 12:46 AM, Anstis, Michael (M.) <manstis1 at ford.com>
> > > > wrote:
> > > >
> > > > > What about Agenda Groups?
> > > > >
> > > > > Rule "pick group X"
> > > > > when
> > > > > Fact( attribute = "condition1" )
> > > > > then
> > > > > drools.setFocus("Group X")
> > > > > end
> > > > >
> > > > > Rule "pick group Y"
> > > > > when
> > > > > Fact( attribute = "condition2" )
> > > > > then
> > > > > drools.setFocus("Group Y")
> > > > > end
> > > > >
> > > > > Rule "Group X1"
> > > > > Agenda Group "Group X"
> > > > > when
> > > > > Smurf( )
> > > > > then
> > > > > // Do something
> > > > > end
> > > > >
> > > > > Rule "Group X2"
> > > > > Agenda Group "Group X"
> > > > > when
> > > > > Smurfette( )
> > > > > then
> > > > > // Something else
> > > > > end
> > > > >
> > > > > etc
> > > > >
> > > > > ------------------------------
> > > > > *From:* rules-users-bounces at lists.jboss.org [mailto:
> > > > > rules-users-bounces at lists.jboss.org] *On Behalf Of *Jai Vasanth
> > > > > *Sent:* 31 January 2008 19:45
> > > > > *To:* rules-users at lists.jboss.org
> > > > > *Subject:* [rules-users] Grouping rules
> > > > >
> > > > > Hi,
> > > > >
> > > > >
> > > > > I am building a system where I would need to fire different sets
> > > > > of rules based on some attribute in the fact object.
> > > > >
> > > > > Here are someways which I thought of, I was wondering if there was
> > > > > something better than that.
> > > > >
> > > > > 1) I could do this by creating different sessions based on the
> > > > > data attrbute (different sessions would have different rule packages based
> > > > > on the attribute)
> > > > >
> > > > > or
> > > > >
> > > > > 2) Have all the rules fire (all the different sets of rules)
> > > > > irrespective of the attribute and have them insert fact new objects into the
> > > > > working memory. In the second round of rules, collect the (newly made) fact
> > > > > objects based on the attribute and take that action.
> > > > >
> > > > >
> > > > >
> > > > > Thanks
> > > > >
> > > > > Jai
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > _______________________________________________
> > > > > rules-users mailing list
> > > > > rules-users at lists.jboss.org
> > > > > https://lists.jboss.org/mailman/listinfo/rules-users
> > > > >
> > > > >
> > > >
> > > > _______________________________________________
> > > > rules-users mailing list
> > > > rules-users at lists.jboss.org
> > > > https://lists.jboss.org/mailman/listinfo/rules-users
> > > >
> > > >
> > >
> >
> > _______________________________________________
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> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
> >
>
>
> --
> Edson Tirelli
> JBoss Drools Core Development
> Office: +55 11 3529-6000
> Mobile: +55 11 9287-5646
> JBoss, a division of Red Hat @ www.jboss.com
>
>
> _______________________________________________
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> rules-users at lists.jboss.org
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>
>
--
Edson Tirelli
JBoss Drools Core Development
Office: +55 11 3529-6000
Mobile: +55 11 9287-5646
JBoss, a division of Red Hat @ www.jboss.com
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