10:26 a.m.
Greetings,
I am working on a collaborative platform project which will contain datas,
informations and knowledges
such as buisness rules. Consequently, a rule engine is a requisite and I am
testing the Drools suite.
Because a lot of different people will be able to define rules, some
combinations might be contradictory.
So the rule user need to know which rules are in conflict, and eventually
choose the ones to disabled to fix the problem.
Here is my use case : I fill in a java class some information about a
people, his hame and his age, and I want to check if he is an adult.
Two different users have written a rule to check this. The first, living in
place where a 18 years old people is an adult wrote this rule :
___________________________________________
rule "Is Major"
when
$a : Applicant (age >= 18)
then
$a.setMajor( true );
end
___________________________________________
The second one, write this one :
___________________________________________
rule "Is Minor"
when
$a : Applicant (age < 21)
then
$a.setMajor( false );
end
___________________________________________
I've tried to solve this knowledge base with a 19 years old people, but no
conflict was detected.
In fact the rules are executed sequentially and the result depends of the
order the rules are called.
My use case is very simple, but I think I am not considering it correctly.
Or maybe it is impossible with forward chaining ?
Does anyone can help me to solve this problem, by telling what is wrong or
giving me some internet ressource link ?
Thanks a lot in advance.
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11:10 a.m.
An approach that may work is to decouple the suggested results from the model with support
for multiple values.
To do this you could define an fact type of Affirmation(String name, Object subject,
Object value).
Where the names are a list of well known values.
You rules would then look like the following:
rule "Is Major"
when
$a : Applicant (age >= 18)
then
insert(new Affirmation("IsMajor", $a, true));
end
rule "Is Minor"
when
$a : Applicant (age < 21)
then
insert(new Affirmation("IsMajor", $a, false));
end
you can then look for contradictions with a rule like the following
rule "contradiction"
when
$aff1 : Affirmation()
$aff2 : Affirmation(this != aff1, name == $aff1.name, subject ==
$aff1.subject, value != $aff1.value)
then
//is both true and false, 3 and 5 etc
end
Obviously there are various way this could be enhanced or done - the affirmations could
include the rule name to allow you to pinpoint which ones are producing contradictory
results etc. You would also have some lower salience rules to actually populate your real
facts with the actual results if a contradiction didn't occur.
Thomas
-----Original Message-----
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-
bounces(a)lists.jboss.org] On Behalf Of AlisterC
Sent: 11 March 2011 09:27
To: rules-users(a)lists.jboss.org
Subject: [rules-users] Conflict detection problem
Greetings,
I am working on a collaborative platform project which will contain
datas,
informations and knowledges
such as buisness rules. Consequently, a rule engine is a requisite and
I am
testing the Drools suite.
Because a lot of different people will be able to define rules, some
combinations might be contradictory.
So the rule user need to know which rules are in conflict, and
eventually
choose the ones to disabled to fix the problem.
Here is my use case : I fill in a java class some information about a
people, his hame and his age, and I want to check if he is an adult.
Two different users have written a rule to check this. The first,
living in
place where a 18 years old people is an adult wrote this rule :
___________________________________________
rule "Is Major"
when
$a : Applicant (age >= 18)
then
$a.setMajor( true );
end
___________________________________________
The second one, write this one :
___________________________________________
rule "Is Minor"
when
$a : Applicant (age < 21)
then
$a.setMajor( false );
end
___________________________________________
I've tried to solve this knowledge base with a 19 years old people, but
no
conflict was detected.
In fact the rules are executed sequentially and the result depends of
the
order the rules are called.
My use case is very simple, but I think I am not considering it
correctly.
Or maybe it is impossible with forward chaining ?
Does anyone can help me to solve this problem, by telling what is wrong
or
giving me some internet ressource link ?
Thanks a lot in advance.
--
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engine.46999.n3.nabble.com/Conflict-detection-problem-
tp2664121p2664121.html
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11:35 a.m.
Thanks a lot, Thomas. I am going to test this decoupled approach.
Alister
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2:04 p.m.
Some other techniques:
(1) Authors must avoid "magic numbers". Define constants such as
MAX_MINOR_AGE in Java. Compiled rules could be inspected to detect literals.
(2) getters can be written to compare the old value against the argument.
(This may mean that simple types have to be avoided in fact classes to have
null as an indication.)
(3) You could use Property Change Listener, which could also be used to
inform the engine about fact changes.
(4) Listening for Working Memory Events in combination with Activation
Events could be used in combination with Java reflection to detect duplicate
updates.
-W
On 11 March 2011 11:35, AlisterC <alister.crepy(a)dps-fr.com> wrote:
Thanks a lot, Thomas. I am going to test this decoupled approach.
Alister
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3:52 p.m.
Thank you Wolfgang. I am a beginner with Drools, so it might take me some
time to experimente these ways. But I'll give my feedback in the next days.
Alister
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8:40 p.m.
You can also take a look at drools-verifier:
http://community.jboss.org/wiki/DroolsVerifier
Best Regards,
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Esteban Aliverti
- Developer @ http://www.plugtree.com
- Blog @ http://ilesteban.wordpress.com
On Fri, Mar 11, 2011 at 11:52 AM, AlisterC <alister.crepy(a)dps-fr.com> wrote:
Thank you Wolfgang. I am a beginner with Drools, so it might take me
some
time to experimente these ways. But I'll give my feedback in the next days.
Alister
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5 comments
4 participants
participants (4)
-
AlisterC -
Esteban Aliverti -
Swindells, Thomas -
Wolfgang Laun