[rules-users] Dynamic facts

[Marc Heinz]

Thank you for your response, Wolfgang.

>> The current documentation always list the "insert" method of a
>> StatefulKnowledgeSession being able to take an additional boolean
>> argument, stating that the corresponding fact supports the
>> PropertyChangeSupport related methods.
>>
>> However, it seems that this method do not exists anymore for already
>> some
>> time now...
>>
>
> It's still there in KnowledgeHelper - not in the "stable" part of the API,
> though. But using this method is not a good choice, IMHO.

Hum ok, the documentation stills need to be updated though...

> It should work, e.g.:
>
>   declare SomeType
>     @propertyChangeSupport(true)
>   end
>
> Although in 5.2.0 there are some severe issues when building using a
> change
> set, which might make this "disappear".

Understood, I may give it another try. But in all cases, I don't feel
comfortable in relying on features that are not described in the API, nor
the documentation.

>> If we effectively can't fire update targeted to some specific fields,
>> this
>> has probably some big implications on performances (even for simple fact
>> with only a few fields).
>
>
> No. Rete has been designed to cope with just that.

I'm not sure to fully understand this statement... If i take the following
rules:
=================================
rule "Single rule check age"
when
	p : Person( age > 18 )
then
	System.out.println("Single rule fired");
end

rule "Rule 1 of n"
    when
        p : Person( name.equals("Adam") )
    then
        System.out.println("Rule 1 of n fired");
end

// [...] hundred of others similar rules that will perform a check on the
// name attribute.
=================================

And with the following java code:

Person p = new Person();
p.setAge(22);
p.setName("Adam");
FactHandle fh = ksession.insert(p);
ksession.fireAllRules();
p.setAge(23);
ksession.update(fh, p);
ksession.fireAllRules();

This will actually produce the output:
Rule 1 of n fired
Single rule fired
Rule 1 of n fired
Single rule fired

So, despite I have only updated one attribute of the fact (the age of a
Person), all rules have been fired again, even if they had nothing to do
with the said attribute, which could possibly produce a huge overhead.

I maybe misunderstood some basic concept here... But is there a way to
prevent that?

For example, I expect a different behavior when using a
PropertyChangeSupport object that would fire events only for specific
fields (but I wasn't able to test it yet)...

Thanks,
Marc