   Hi Aldian,

   I think you misunderstood the semantics of forall(). Forall in Drools is the same forall quantifier from the First Order Logic.

http://en.wikipedia.org/wiki/First-order_logic

   So, if you want to write a rule that says: "When for all equipments of type 'router' there is an alarm, then raise a general failure alarm".

when
    forall( $e : Equipment( type == "router" )
             Alarm( source == $e ) )
then
    // raise a general failure alarm
end

    So, if you have 10 routers in the working memory and only 9 of them have associated alarms, this rule will NOT fire, because the condition is not matched. But, if an alarm is raised for the 10th router, then all of them have an associated alarm and the rule will fire.

    So, as you can see, "forall" is a quantifier CE, in the same way that "not" and "exists" are quantifiers. They operate on multiple facts at once, and as so, you can not use the variables bound inside their scope outside of it. In the above example, if you tried to use $e in the consequence, which of the 10 routers would it be bound to? So, since it makes no sense, the engine disallow the usage of variables bound inside quantifiers outside of them.

    Just to be easier to remember I call quantifier CEs "scope delimiters". The general rule is: variables bound inside a scope delimiter are never available outside of them.

    I don't understand what you are trying to do in your first rule in your example. If you write your rule in plain English, the people from the list can help you write it correctly.

    Finally, just for completeness, be careful with the semantics of time. Your Alarm class is using the system clock to define timeout, and that will give you all kinds of headaches, not to mention wrong/unexpected results. But this e-mail is already too long. I suggest you take a look at the Drools Fusion docs on temporal reasoning.

    []s
    Edson

2009/7/10 Gab Aldian <aldian.gp@gmail.com>

Hi everybody

I have read with attention the drools expert documentation, which was
very interesting, but a little 'too simple". For example, most
examples don't present rules with the keyword "forall". I also met big
difficulties mixing the references on the objects to my javacode. This
is why I would need some more documentation with examples that go
deeper into drools capacities.

To give you clues about my plan, here is an example (which works
perfectly in drools 5) that I have developed:
java code - http://drools.pastebin.com/m1a705614
rule code - http://drools.pastebin.com/m3f30cbdc

As you can see I am studying the case where drools is used for the
monitoring of a network of equipments that send alarms about their
problems. But I have big difficulties, because I would like to get
references on the objects of the "forall", and to execute javacode
such as $toto.method($titi, $tata), but such things seems impossible
(systematic failed of compilation)

Could you please help me?

Thank you very much!

Aldian
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Edson Tirelli
JBoss Drools Core Development
JBoss by Red Hat @ www.jboss.com