Specifically speaking, here is what I get on Eclipse when I do that:


nds.when cannot be resolved to a type                                                 MPU/src/rules    EEphratOBMain.drl    line 11   
Syntax error on token ":", ; expected                                                    MPU/src/rules    EEphratOBMain.drl    line 11   
Syntax error on token ""Definitions TermContractions 1.1"", . expected    MPU/src/rules    EEphratOBMain.drl    line 11   
Syntax error on token "then", invalid AssignmentOperator                       MPU/src/rules    EEphratOBMain.drl    line 11   
Syntax error, insert ";" to complete Statement                                       MPU/src/rules    EEphratOBMain.drl    line 11   
Syntax error, insert ";" to complete Statement                                       MPU/src/rules    EEphratOBMain.drl    line 11   
Syntax error, insert ";" to complete Statement                                       MPU/src/rules    EEphratOBMain.drl    line 11   

Line 11 is:

rule "TermContractions 2.8" extends "Definitions TermContractions 1.1"

and "Definitions TermContractions 1.1" is another rule defined in the same drl.


On Fri, Mar 5, 2010 at 12:04 PM, Moe Alkhafaji <moe.alkhafaji@medcpu.com> wrote:
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@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@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.

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 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@medcpu.com

This message contains information which may be confidential. Unless you are the addressee, you may not use, copy or disclose to anyone the message or any information contained in this message. If you have received this email in error, please notify cto@medcpu.com and please delete the message immediately. In order for the contents of this message to be binding on behalf of MedCPU it must be confirmed in writing by an authorized signatory of MedCPU. Our company accepts no liability for the content of this email unless it is so confirmed. The views or opinions presented herein do not necessarily represent those of the company.



--
Moe Alkhafaji
Chief Technology Officer, MedCPU
Phone: (630) 290-1113
Email: cto@medcpu.com

This message contains information which may be confidential. Unless you are the addressee, you may not use, copy or disclose to anyone the message or any information contained in this message. If you have received this email in error, please notify cto@medcpu.com and please delete the message immediately. In order for the contents of this message to be binding on behalf of MedCPU it must be confirmed in writing by an authorized signatory of MedCPU. Our company accepts no liability for the content of this email unless it is so confirmed. The views or opinions presented herein do not necessarily represent those of the company.