[rules-users] Discover when a rule isn't more active

[Ingomar Otter]

There is a mechanism called truth maintenance ensuring for example

A -> B
B -> C

that C becomes false when it's premise (B) becomes false as well.
What it basically does it track the LHS side of the rule and undoes  
asserted facts when there are no more "facts" to support it (activate  
the rules in question).
Look at the documentation for logicals / truth mainteance. It's pretty  
cool.

For your case:

rule "light2on"
when
	LIght(name=="0/0/2", actualvalue=="1")
then
       insertLogical( new LightIsOn(2))
end

the fact "LightIsOn" will only be true (in the working memory) as long  
as the LHS of the rule above is still true. For example if acutalvalue  
becomes 0, that fact would vanish automagically.
That implies that you use facts to make statements about your system  
(not using behind the scene callbacks) - but from my very little  
experience I would say this is a good practice anyway. Fiddeling with  
activations make me suspicious ;-) - But then it all depends on your  
particular problem at hand.

--I


>>> rule "light 2 on"
>>> dialect "java"
>>> when
>>> Light (name=="0/0/2", actualvalue=="1");
>>> then
>>> System.out.println("luce 2 on");
>>> end


Am 29.07.2008 um 14:42 schrieb Claudio Rainoldi:

> i'm sorry i'm a new drools user.. Can you try to be a little more  
> clear?
> thanks..
>
>
> 2008/7/29, Ingomar Otter <iotter at mac.com>:
>>
>> Use logicals.
>>
>> Am 29.07.2008 um 11:20 schrieb Claudio Rainoldi:
>>
>> Hi everyone,
>>> isn'it there a way to find when a rule isn't more active.
>>> For example if i have this rule:
>>>
>>>
>>> rule "light 2 on"
>>> dialect "java"
>>> when
>>> Light (name=="0/0/2", actualvalue=="1");
>>> then
>>> System.out.println("luce 2 on");
>>> end
>>>
>>>
>>> when someone turn on the light 2 i discover that the rule is fired  
>>> using
>>> an
>>> Agenda Event Listener and the method afterActivationFired;
>>> But when someone turn off the ligth isn't there a similar way to  
>>> discover
>>> that the rule "light 2 on" isn't more active.
>>> My only solution is to use the dual rule:
>>>
>>> rule "light 2 on_dual"
>>> dialect "java"
>>> when
>>> not (Light (name=="0/0/2", actualvalue=="1"));
>>> then
>>> System.out.println("luce 2 off");
>>> end
>>>
>>> Isn't there a more sample way to do this?
>>> Thanks in advance.
>>>
>>>
>>> Cla
>>> _______________________________________________
>>> 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
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