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@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@lists.jboss.org [mailto:rules-users-bounces@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@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@lists.jboss.org [mailto:rules-users-bounces@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@gmail.com> wrote:
Thanks.  That helped.


On Feb 1, 2008 7:31 AM, Anstis, Michael (M.) <manstis1@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

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@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@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Jai Vasanth
Sent: 31 January 2008 19:45
To: rules-users@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





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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

_______________________________________________
rules-users mailing list
rules-users@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