Re: [rules-users] Cutom Attributes in Drools

[dme1]

Hi Davide,

For my case, whats proposed in Example #1 would suffice with the activations
being overridden i.e. the Rule "High" should completely override Rule "Low"
which should not be activated, and the outcome should be only one log (A)
and the policy should be set to A.

Example#2 for my case would be 2 separate rules as far as the definition is
concerned, Rule High applies only when the Car Type matches, otherwise rule
Low would be fired. I am not considering the impact of retracting Car during
runtime.

Thanks,
dme



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Re: [rules-users] Cutom Attributes in Drools

[Davide Sottara]

Hi, 
this is definitely something in scope for the type of "Defeasible rules" i'm
working on right now.
I have just one last question:
do you need the second rule to override the activation of the first, or do
you need the VALUE set
by the second rule to override the value set by the first?
In your example, the effect would be the same, but let me show two other
examples:
(Also please notice the currently proposed metadata)

Example #1
rule "High"
@Defeasible
@Cuts( "Low" )
when
  $p : Person( age > 25 )
then
  $p.setPolicyType( "A" );
  *log( "A policy"  );*
end

rule "Low"
@Defeasible
when
  $p : Person( age > 25 )
then
  $p.setPolicyType( "B" );
  log( "B policy" );
end

If you just override the values, you'll see TWO logs and $p.policyType ==
"A".
If you override the activations, only the consequence of "High" will fire.
The attributes here would override the activations: notice that, unlike
salience, the activation
of High will prevent the activation of Low altogether


Example #2 :

rule "High"
@Defeasible
@Defeats( "Low" )
when
  $p : Person( age > 25 )
  $c : Car( color == "red" )
then
  $p.setPolicyType_Logical( "A" );  // syntax to be determined yet! 
end

rule "Low"
@Defeasible
when
  $p : Person( age > 25 )
then
  $p.setPolicyType_Logical( "B" );
end

In this case, the override would be at the value level: unlike salience or
the previous example,
here the TMS will keep track of both attempts at setting the policy type
value. This means that
the policyType will be "A" BUT, should e.g. the Car be retracted, the
policyType will automatically
be modified to "B" since now that unblocked "set" would support the value.
(This case will actually require some more time to support)

Davide





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Re: [rules-users] Cutom Attributes in Drools

[dme1]

Thanks Davide.

Regarding "Multiple LHS and RHS.", this comment refers to the need for
Custom Attributes,and is not related to Overriding Rules. To elaborate I was
looking for a way for the Rules to fire when some Attributes are set
(multiple LHS) as well as for the rule set some attributes if/when fired
(multiple RHS), and you and others have satisfactorily answered with the
options available with Drools (including Metadata) which will allow me to
achieve this (albeit with some limitations).

Regarding Overridden Rules - We have scenarios where we need the Rule to
behave differently for lets say a specific customer or a specific territory.
These rules could be rules that validate conditions, or rules that calculate
values. 

A simple example could be 

Default Common Rule:
when 
  p : Person (age >= 25)
then
  p.setPolicyType("Premium");

A rule that overrides this would be lets say for Region X:
when
  p : Person (age >= 25)
then
 p.setPolicyType("Extensive");

In theory this can be done using a check for Region "X" within another rule.
However we have a rule-flow where this rule would be part of the flow, as
well as multiple rules within the flow, which depend on the result of the
value from this rule. SO rather than having a separate flow for each region
we would like to have a common flow, and the rule fired should depend on if
there is an overridden rule for the Region, if not use the default rule.

Ideally I would like to create a separate Project/Package in Guvnor for the
Region since we have enough differences, and for rules to be overridden
across packages, but this I don't think will be possible in Drools as I did
not see a way of specifying package dependencies and using rule flow define
in one package in another package.

Hope this provides a good use case for what we are trying to achieve.

Thanks,
dme




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Re: [rules-users] Cutom Attributes in Drools

[Davide Sottara]

The feature is being implemented even now, I will make available
incrementally over the next 10 days or so, unless I get preempted by too
many other matters :) As you may know, I'm not part of the Drools team
so I am not working 100% on this. It may take some more time to document and
release it officially, but
I can show you the principles once it's in place - and of course it really
fits your requirements!

It would be invaluable if you could provide some toy, deintified test cases
to show your expected behavior.
I'd like to better understand what kind of ovverrides you need exactly - and
btw I'm struggling a bit to 
understand what you mean with "choice between multiple elements LHS and
RHS"...
Thanks
Davide



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Re: [rules-users] Cutom Attributes in Drools

[dme1]

Thanks for the suggestions. However I have rules where the Control Fact is
not mandatory, as well as there is a choice between multiple elements (LHS
and RHS) so I have to come up with a Dummy which says something like does
not apply to this rule, a bit cumbersome but an approach that can be
explored.

@Davide - For the override rules, are you able to advise when this feature
will be available? Also in the interim is there a workaround that can be
used to simulate this feature?

Thanks,
dme



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Re: [rules-users] Cutom Attributes in Drools

[Davide Sottara]

Thank you for reporting this user experience... and I think this is of
interest for other users too.
I would address your problem at different levels..

You basically are asking for a more declarative approach to writing business
rules, and that is perfectly
understandable. The DRL rules are "technical" rules and are somewhat in
between a purely declarative
language and a programming language.

This said, "rules should fire or not depending on the context": if that
context is part of the business logic, i.e. lives at the same level of the
other preconditions, it should be added to the premises of the rules, 
and now the problem is finding a better language for your knowledge
engineers to model business rules.

If instead the logic can be understood to be a "meta-level" logic, so that
you'd have to create
"innatural" auxiliary control facts, you could possibly explore the
meta-rule approach I outlined in my previous comment. Of course, this still
suffers from the same technicality issue, but the rules would
be written by the business users and the meta rules by the technical ones...
(btw The reason for not updating metadata is that they are defined
statically at the rule level, whereas you would actually be interested in
the activations! and this is quite different)

Also remember that Drools is community driven: if you think that there is
some missing feature, please
submit a proposal (e.g. would something like SBVR be more suitable for
you?), maybe others will join
you in supporting that. A "critical mass" may help to get it done, and of
course you can help and contribute :)



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Re: [rules-users] Cutom Attributes in Drools

[Vincent LEGENDRE]

It is not a myth ... but indeed, it's hard. 
Most of times, you have to find one guy at client's side who is ready to learn 
at least the main principles of expert-systems. For my experience, it works 
well enough (ie most of rules dev time is done by the BA) in about 1 proj out 
of 3. For the others, an IT guy is still needed to help the BA (which is 
something doable if you have enough rules to author). 

DSL are hard to set, and harder to maintain, especially while using guvnor 
(using DSL in a dsrl rule is fine, but dsrl rules for non-IT guys is a myth). 
Usually I try as much as I can to set a business-compliant POJO model (ie 
simple, almost flat, with fields named in a way they understand what is behind) 
and no DSL at all... 
For the rules' firing control, it is harder ... 

@dme1 : May be you can think on an agenda filter that looks for the rule's 
package ? Or use "category rules", which is a rule binded to a category, which 
acts as a parent rule for all rules under this category (so all rules of the 
same category will have the same common first conditions, which can be the test 
of your control fact). But beware of that, there was a bug on sub-categories, 
or when a rule has more than one category (one the first category is taken if I 
remember well). A last thing could be to use verifier to ensure that all rules 
have a first condition that test the control fact . 

@GPatel : your approach sounds great. How much time did you spent to write such 
a Guvnor alternative ? 


- Mail original -

De: gpa...@tsys.com 
À: "Rules Users List"  
Envoyé: Jeudi 13 Septembre 2012 18:47:52 
Objet: Re: [rules-users] Cutom Attributes in Drools 

" I would not store the result of the (missed) activation of a rule in a rule 
attribute, anyway. Can't you just use a dedicated fact(s) for that?" 

I face a similar issue where the target audience are "business" users i.e users 
that dont really understanding or wish to get into logic. I am finding myself 
having to resort to all sorts of tricks (using categories/packages/standlone 
rule editor) to allow business users to easily specify which rules are for what 
purposes and when they should fire. I just cant rely on them using facts 
correctly to disable rules that should not fire. In fact, I am now down to 
using only the standalone editor and saving the rule xml in my tables (not 
guvnor) so that i have full control over itemized rule display, rule search, 
knowledgebase creation for different execution profiles, etc. 

Overall, I increasingly tend to think rules for business users is a myth. The 
business users wants rule-driven systems, yet they dont want to learn drools. 
And drools DSL just doesnt cut it. 



From: Davide Sottara  
To: rules-users@lists.jboss.org, 
Date: 09/13/2012 01:57 AM 
Subject: Re: [rules-users] Cutom Attributes in Drools 
Sent by: rules-users-boun...@lists.jboss.org 




You can add any metadata using the format @name( "value" ) or @name( 
key=value ). You can then look them up using rule.getMetaData(). 
Please notice that there's a bug (solved by an open pull request) that does 
not let you write just @name. 

In order to use those attributes to control whether a rule fires or not, you 
can use the "declarative agenda", i.e. add meta-rules to your knowledge base 
such as: 

rule "Meta" 
@activationListener('direct') 
when 
// assuming the attribute is @region( [value] ) 
$a : Activation( rule.metaData[ "name" ] != "MyDesiredRegion", $objs : 
objects ) 
// any condition on the tuple here, if needed 
then 
drools.cancelActivation( $a ); 
end 

notice that you'll have to enable the corresponding option first: 
KnowledgeBaseConfiguration kconf = 
KnowledgeBaseFactory.newKnowledgeBaseConfiguration(); 
kconf.setOption( DeclarativeAgendaOption.ENABLED ); 
KnowledgeBase kb = KnowledgeBaseFactory.newKnowledgeBase( kconf ); 


If you want to have rules override each other, watch out for an upcoming 
feature, "Defeasible logic". 
I would not store the result of the (missed) activation of a rule in a rule 
attribute, anyway. Can't you 
just use a dedicated fact(s) for that? 

Best 
Davide 



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Re: [rules-users] Cutom Attributes in Drools

[GPatel]

"I would not store the result of the (missed) activation of a rule in a 
rule
attribute, anyway. Can't you just use a dedicated fact(s) for that?"

I face a similar issue where the target audience are "business" users i.e 
users that dont really understanding or wish to get into logic. I am 
finding myself having to resort to all sorts of tricks (using 
categories/packages/standlone rule editor) to allow business users to 
easily specify which rules are for what purposes and when they should 
fire. I just cant rely on them using facts correctly to disable rules that 
should not fire. In fact, I am now down to using only the standalone 
editor and saving the rule xml in my tables (not guvnor) so that i have 
full control over itemized rule display, rule search, knowledgebase 
creation for different execution profiles, etc.

Overall, I increasingly tend to think rules for business users is a myth. 
The business users wants rule-driven systems, yet they dont want to learn 
drools. And drools DSL just doesnt cut it.



From:   Davide Sottara 
To: rules-users@lists.jboss.org, 
Date:   09/13/2012 01:57 AM
Subject:    Re: [rules-users] Cutom Attributes in Drools
Sent by:rules-users-boun...@lists.jboss.org



You can add any metadata using the format @name( "value" ) or @name(
key=value ). You can then look them up using rule.getMetaData(). 
Please notice that there's a bug (solved by an open pull request) that 
does
not let you write just @name.

In order to use those attributes to control whether a rule fires or not, 
you
can use the "declarative agenda", i.e. add meta-rules to your knowledge 
base
such as:

rule "Meta"
@activationListener('direct')
when
// assuming the attribute is @region( [value] )
$a : Activation( rule.metaData[ "name" ] != "MyDesiredRegion", $objs :
objects )
// any condition on the tuple here, if needed
then
drools.cancelActivation( $a );
end

notice that you'll have to enable the corresponding option first:
KnowledgeBaseConfiguration kconf =
KnowledgeBaseFactory.newKnowledgeBaseConfiguration();
kconf.setOption( DeclarativeAgendaOption.ENABLED );
KnowledgeBase kb = KnowledgeBaseFactory.newKnowledgeBase( kconf );


If you want to have rules override each other, watch out for an upcoming
feature, "Defeasible logic".
I would not store the result of the (missed) activation of a rule in a 
rule
attribute, anyway. Can't you
just use a dedicated fact(s) for that?

Best
Davide



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Re: [rules-users] Cutom Attributes in Drools

[dme1]

Davide,

Thanks for the suggestions. I was considering using the MetaData as well,
since it allows both evaluation on the LHS (just like the example you have)
as well as on the RHS where I can get the MetaData through code and use it
in the application.

And like you have suggested I can use dedicated Fact Types for the RHS, the
requirement for us is also for our business users to be able to set these
attributes/properties when creating or updating a rule in Guvnor, so having
a predefined list (attribute name as well as the values) to choose from
makes it easier and error free, and since its not possible with MetaData I
was wondering if there is another way to achieve this with Custom
Attributes.

Also thanks for the heads up on "Rule Overridability" features being added.
The current scenario I was trying to solve is where certain rule would
generate a Hard Stop for the application process (Non Overridable), while
others would generate a Confirmation message for the users to acknowledge
and continue or to abandon processing (Overridable). And since all rules in
our environment have to set this property I was wondering if we could do
this with a Custom Attribute that could be set by the rule (only when it
fires) and evaluated in the application to determine the course of action to
take.

Again thanks for your response, and I now understand the options available.

dme



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Re: [rules-users] Cutom Attributes in Drools

[Davide Sottara]

You can add any metadata using the format @name( "value" ) or @name(
key=value ). You can then look them up using rule.getMetaData(). 
Please notice that there's a bug (solved by an open pull request) that does
not let you write just @name.

In order to use those attributes to control whether a rule fires or not, you
can use the "declarative agenda", i.e. add meta-rules to your knowledge base
such as:

rule "Meta"
@activationListener('direct')
when
// assuming the attribute is @region( [value] )
$a : Activation( rule.metaData[ "name" ] != "MyDesiredRegion", $objs :
objects )
// any condition on the tuple here, if needed
then
drools.cancelActivation( $a );
end

notice that you'll have to enable the corresponding option first:
KnowledgeBaseConfiguration kconf =
KnowledgeBaseFactory.newKnowledgeBaseConfiguration();
kconf.setOption( DeclarativeAgendaOption.ENABLED );
KnowledgeBase kb = KnowledgeBaseFactory.newKnowledgeBase( kconf );


If you want to have rules override each other, watch out for an upcoming
feature, "Defeasible logic".
I would not store the result of the (missed) activation of a rule in a rule
attribute, anyway. Can't you
just use a dedicated fact(s) for that?

Best
Davide



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[rules-users] Cutom Attributes in Drools

[dme1]

Hi,

Is there support for Custom Attributes in Drools? What I want to do is add
attributes which determines when rules should be fired as well as attributes
that the rule updates which I can query at a later time.

E.g. Fire rule only for specific regions. So when new rules are
created/added BAs can define if it is applicable to specific regions.

Then the rule could result in a violation that could or could not be
overriden, so I want to add an attribute called override which is set by the
rule, which I can check after all rules are fired. I can use MetaData to
define this, but I need a pre-defined list which BAs can choose from when
creating a new rule.

Any thoughts on how I can implement this would be appreciated.

Thanks,
dme




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