[rules-users] Trouble getting Dynamic Salience working - add in rules-templates
Bill Tarr
javatestcase at yahoo.com
Wed Sep 2 03:26:01 EDT 2009
Thank you for the response Greg. For starters, I did NOT know about specificity... very helpful to know, and I feel certain I will be using it in the future. I don't feel any of the documentation I've read on Drools really got this subject across for me, I not sure the the Drools developer book really covers it at all.
Back to my actual implementation. We are using rules-templates, which have a "unique behavior" I've been calling a feature, but some might consider a bug... or have found a way to work around. Templates do not render rule lines which contains NULL parameters. This hasn't bit my too badly to this point, but MAY pose an interesting issue for specificity (now that I know about it!)
My real world example is a good bit more complicated. My LH includes:
PARAMETERS
--------------------------
Product - NOT NULL
Start Date
End State
Price Group - NOT NULL
State Group
Some of the info is coming from a single instance of an object I'm calling "transporter" I use to gather info from other rules. It will have a list of state groups and price groups. So psuedocode for my template LH will look something like:
template.pricegroups.contains( "@{PRICE_GROUP}" )
template.stategroups.contains( "@{STATE_GROUP}" )
policy (
startDate > @{START_DATE}
endDate < @{END_DATE}
product = "@{PRODUCT}"
)
The problem I run into here, is that in any given rule, only a subset of these will appear. So one rule may produce:
// this rules parameters have a NULL STATE_GROUP
template.pricegroups.contains( "pg1" )
policy (
startDate > 2009-01-01
endDate < 2010-01-10}
product = "prod1"
)
and another might produce
// this rule has a STATE_GROUP, but no START_DATE and END_DATE
template.pricegroups.contains( "pg1" )
template.stategroups.contains( "NY" )
policy (
product = "prod2"
)
In this example, I actually want the SECOND rule to win the conflict. It is "more specific" for our business rule, a policy for NY should match, but the the first rule should not. In reality, the first rule has more facts, so which one will actually fire first by rules of specificity?
My activation-group and salience hack was one workaround for this condition. I set the second rule with a higher salience, and add them both to the same activation-group.
I will try different combinations of rule-templates and specificity when I am in the office tomorrow (midnight here in San Diego.) If you have any further feedback on this, I do appreciate your taking the time to show a Drools newbie some very useful stuff.
Thanks!
Bill
Message: 2
Date: Tue, 1 Sep 2009 19:29:40 -0700 (PDT)
From: Greg Barton <greg_barton at yahoo.com>
Subject: Re: [rules-users] Trouble getting Dynamic Salience working
To: Rules Users List <rules-users at lists.jboss.org>
Message-ID: <52492.42683.qm at web81501.mail.mud.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"
I hope you're not going through all of that trouble just to get the functionality from that concrete example. You get that for free with Drools' default conflict resolution, which includes "specificity." Specificity means that rules with the more specific conditions, and all else equal, are fired first. So between these two rules, only the CheeseSausagePepperoniPepper one fires:
rule "CheeseOnly"
when
p : Pizza( )
t1: Topping( pizza == p, name == "cheese" )
then
System.out.println( "Eating cheese pizza" );
retract( t1 );
retract( p );
end
rule "CheeseSausagePepperoniPepper"
when
p : Pizza( )
t1: Topping( pizza == p, name == "cheese" )
t2: Topping( pizza == p, name == "sausage" )
t3: Topping( pizza == p, name == "pepperoni" )
t4: Topping( pizza == p, name == "pepper" )
then
System.out.println( "Eating cheese sausage pepperoni pepper pizza" );
retract( t4 );
retract( t3 );
retract( t2 );
retract( t1 );
retract( p );
end
See the attached project.
--- On Tue, 9/1/09, Bill Tarr <javatestcase at yahoo.com> wrote:
> From: Bill Tarr <javatestcase at yahoo.com>
> Subject: [rules-users] Trouble getting Dynamic Salience working
> To: rules-users at lists.jboss.org
> Date: Tuesday, September 1, 2009, 7:28 PM
> We have a winner!? Many thanks
> Michal, hope I can return the favor one day.
>
> salience ( return getSalience4() )
>
> for the record, my function looks something like (after
> tempate evaluation):
>
> <pre>
> function int getSalience4(){
> ??? int salience = 0;
> ??? if("VALUE"=="VALUE") salience += 1000;
>
> ??? return salience;
> }
> </pre>
>
> I think the combination activation-group and dynamic
> salience for rule-template projects are pretty useful.
>
> Just for anyone interested,?the tempate code looks
> something like this:
>
> <pre>
> rule "Some Rule_@{row.rowNumber}"
>
> ??? activation-group "@{PARAM1}-@{PARAM2}"
> ??? salience ( return getSalience@{row.rowNumber}() )
> </pre>
>
> where PARAM1 and PARAM2 make up a kind of key. I only want
> to execute one rule that matches that key, no matter how
> many options there are.
>
> Rules that have additional parameters get higher salience
> than rules with less parameters, so here is my function.
>
> <pre>
> function int getSalience@{row.rowNumber}(){
> ??? int salience = 0;
> ??? if("@{PARAM3}"=="@{PARAM3}") salience += 1000;
> ??? if("@{PARAM4}"=="@{PARAM4}") salience += 1000;
> ??? return salience;
> }
> </pre>
>
> A concrete example could be pizza.? So there are?3 types
> of pizza, all are grouped in the same activation-group.
>
> cheese, pepperoni
> cheese, pepperoni, sausage
> cheese, pepperoni, meatball, pepper
>
> Any cheese and pepperoni pizza should could match all these
> rules, but more toppings is always better for me.
>
> So cheese, pepperoni, onion, pepper getts a salience of
> 2000, and is the only rule evaluated.
>
>
>
> On Tue Sep 1 18:39:13 EDT 2009, Michal Bali michalbali at
> gmail.com? wrote:
>
> does this work?
> salience ( return getSalience() )
>
> or this:
>
> salience ( getSalience();)
>
>
> On Tue, Sep 1, 2009 at 6:50 PM, Bill Tarr <javatestcase
> at yahoo.com> wrote:
>
> > Possibily just a simple MVEL error, but I've been
> struggling for a while
> > and thought I'd see if anyone could help.
> >
> > I just want to run a logic test to determine salience
> for some rules I am
> > generating with rules-templates.??Even after making
> the logical test "true"
> > I can't get any of variation to compile.
> >
> > (true ? "1000" : "0")
> > **produces**
> > Unable to build expression for 'salience' : not a
> statement, or badly
> > formed structure
> >
> > ( true ? 1000 : 0)
> > **produces**
> > Unable to build expression for 'salience' : invalid
> number literal: 1000
> >
> > salience ( getSalience() )
> > ...
> > function int getSalience(){return 0;}
> > **produces**
> > Unable to build expression for 'salience' :
> org.mvel2.util.MethodStub
> > cannot be cast to java.lang.Class'(
> getSalienceNONCDW() )'
> >
> > Seems like I am missing something simple, but I've
> tried many variations on
> > the above, and have been unable to find any working
> examples of using a
> > logical test in salience, so if anyone has any
> direction it would be greatly
> > appreciated.
> >
> > Thanks!
> >
> > Bill
>
>
> ? ? ?
>
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