[rules-users] Get rid of redundant conditions in combined rules.

[Leonardo Gomes]

If your problem is performance, don't worry. Conditions evaluation is
shared, so in the second rule you won't re-evaluate the entire working
memory (to know more:http://www.drdobbs.com/184405218).

If you're worried about not having to repeat the conditions on the second
rule, I would create inferred facts when the first rule matches and use then
in the second rule + the additional conditions.

Something like:

Rule1:

when

            customer:Customer(town=="London")

then

            insert new LondonCustomer( customer );



Rule2:

when

            london : LondonCustomer(customer.job=="TEACHER")

then

            System.out.println(london.customer.getLname() + " is a
teacher");


2010/10/12 Dominik Hüttner <d.huettner at tiq-solutions.de>

>  Hello everyone,
>
> I’ve got a question. I’m using drools-guvnor to execute some
> rule-scenarios. I have to solve the following problem: I have an amount of
> objects in my working memory and can’t remove objects from the working
> memory in the then-part of the rule. I want to combine two rules, the first
> rule selects some objects and the second rule checks only these selected
> objects for additional criteria. I have to use two rules, because I want to
> report the objects selected in the first rule, too. Now I have implemented
> this with two rules and in the second rule, the criterias of the first rule
> are copied to the second rule, my question is, is there a way to get rid of
> this redundandance?
>
> I have tried this with a rule flow, but the problem is, this always works
> on the whole working memory, but I can’t remove the not used objects from
> working memory for performance reasons. Is there another way to solve this
> problem?
>
>
>
> Here is an example for what I intend to do:
>
>
>
> Rule1:
>
> when
>
>             customer:Customer(town=="London")
>
> then
>
>             System.out.println(customer.getLname() + " is inhabitant of
> London");
>
>
>
> Rule2:
>
> when
>
>             customer:Customer(town=="London",job=="TEACHER")
>
> then
>
>             System.out.println(customer.getLname() + " is a teacher");
>
>
>
> This example illustrates, with the first rule I want to get to know, how
> many customers are from London and in the second rule I want to know, how
> many of the London customers are teachers. I want to create a kind of
> statistics. I have quite a lot of conditions for the first rule, so I don’t
> want to have them redundantly.
>
>
>
> Greetings, Dominik
>
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>
>
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