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

[Dominik Hüttner]

Hi Leonardo,

the performance problem I thought of meant removing and inserting the facts
again and again, if I would remove the facts, that don’t fit the first rule
and execute the second rule only on the remaining facts. 

The solution you offered, does, what I intend, but the problem is, that I
have to create a new class for every rule-pair and I want to use it
flexible, without having to create a new class / model for every rule. Is
there maybe another way to solve this problem?

 

Kind regards,

 

Dominik

 

 

 

Von: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] Im Auftrag von Leonardo Gomes
Gesendet: Dienstag, 12. Oktober 2010 16:37
An: Rules Users List
Betreff: Re: [rules-users] Get rid of redundant conditions in combined
rules.

 

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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