[rules-users] Inheritance-Like Design Question

[Edson Tirelli]

   Extends is in there since 5.0.0, and should work in eclipse plugin as
well. The integration tests are running fine as well, so there should be no
problem.

   What error did you got?

   Edson

2010/3/5 Moe Alkhafaji <moe.alkhafaji at medcpu.com>

> Thanks Edson, I will try that. However, I have one follow up question. I
> tried to use the "extends" command and it did not work (it gave me a syntax
> error). I am using the latest Drools 5.0 M1. Could it be because the Eclipse
> Drools plugin does not support this feature yet and if I ignore this error
> on Eclipse it would still work at runtime?
>
> Thanks!
>
> 2010/3/5 Edson Tirelli <ed.tirelli at gmail.com>
>
>
>>       Although I noticed the other day that this is not documented yet,
>> Drools 5.0.x does support rule inheritance. In your case, it would be
>> written as:
>>
>> rule r1
>> when
>>    A()
>> then
>>    // do something
>> end
>>
>> rule r2 extends r1
>> when
>>    B()
>> then
>>    // do something else
>> end
>>
>>     When using inheritance, the subrule will inherit the whole LHS of the
>> parent rule.
>>
>>     Integration test here:
>>
>>
>> http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-compiler/src/test/resources/org/drools/integrationtests/extend_rule_test.drl
>>
>> http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-compiler/src/test/resources/org/drools/integrationtests/test_RuleExtend.drl
>>
>>     In your case, you have an extra requirement that if a child rule
>> fires, you don't want the parent rule to fire. My suggestion is either doing
>> this with a logical condition, or adding drools.halt() on the consequence of
>> rules that should stop subsequent firings, or using activation-groups +
>> salience. Example, in the above case, you could have:
>>
>> rule r1
>>    activation-group "example rules"
>>    salience 10
>> when
>>    A()
>> then
>>    // do something
>> end
>>
>> rule r2 extends r1
>>    activation-group "example rules"
>>    salience 20
>> when
>>    B()
>> then
>>    // do something else
>> end
>>
>>    Since rule 2 has a higher salience, if it activates it will fire first,
>> and due to the activation-group, it will cancel the activation of r1
>> preventing it to fire.
>>
>>    Hope it helps.
>>
>>    Edson
>>
>> 2010/3/5 malkhafaji <moe.alkhafaji at medcpu.com>
>>
>>
>>> Hello,
>>>
>>> I know, from searching this forum and posting before, that the concept of
>>> inheritance does not exist today in Drools. However, I have a need for
>>> it.
>>> Here is my specific situation:
>>>
>>> I have certain rules that have some generic conditions to be fired:
>>>
>>> Rule 1
>>> If A Then X end
>>>
>>> Rule 2
>>> If A, B Then Y end
>>>
>>> What I would like to do is, if Rule 2 is true, then I don't want Rule 1
>>> to
>>> execute. I have many and many of those rules, so combining all the
>>> conditions in less number of rules violates our design having rules being
>>> mutually exclusive. That is why I wanted to include this behavior as a
>>> natural inheritance behavior rather than forcing the flow with logic
>>> inside
>>> the rule itself (you will make rules aware of others this way).
>>>
>>> So, since there is not built-in feature that allows you to do that, do
>>> people suggest anything that I can do without having to mix Rule 1 and
>>> Rule
>>> 2 into one rule with complex conditional statements? Any ideas?
>>>
>>> The only thing I can think of is taking this logic processing outside of
>>> drools, which is something that I am not too excited about.
>>>
>>> Thanks.
>>>
>>> --
>>> View this message in context:
>>> http://n3.nabble.com/Inheritance-Like-Design-Question-tp430848p430848.html
>>> Sent from the Drools - User mailing list archive at Nabble.com.
>>> _______________________________________________
>>> rules-users mailing list
>>> rules-users at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/rules-users
>>>
>>
>>
>>
>> --
>>  Edson Tirelli
>>  JBoss Drools Core Development
>>  JBoss by Red Hat @ www.jboss.com
>>
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>>
>>
>
>
> --
> Moe Alkhafaji
> Chief Technology Officer, MedCPU
> Phone: (630) 290-1113
> Email: cto at medcpu.com
>
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-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss by Red Hat @ www.jboss.com
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