[rules-users] Abstracting Rules using extends

[Davide Sottara]

I'm not entering the discussion on the use case, just making a couple of
technical points

1) The rule extension does not work because your rules are defined in
two different packages,
which is currently not supported. There was a similar thread not long ago.
I do agree that at least a warning - if not an error - should be raised
at compile time rather
than causing a late NPE execption. I'll see into that.

2) The "declare RuleConstant" below does not define global variables,
but a class for
which the default constructor would initialize the fields to default values.
You may want to declare an enum instead:

declare enum RuleConstant
    COUPE( "C" ),
    SEDAN( "S" );

    code : String
end

you can then use it as an enum...

Vehicle( type == RuleConstant.COUPE )

or, more likely:

Vehicle( type == RuleConstant.COUPE.code )

assuming that the type field contains Strings such as "C" or "S"

Best
Davide


On 04/05/2013 11:17 AM, Arul Prashanth wrote:
> Thanks Laune for your insight. 
>
> 1. The idea of having RuleConstant in the workingMemory is that the
> constants are defined in a drl and is being inserted into the working memory
> by a high salience rule. This is to reduce the effort in actual  application
> build and deployment rather just package the rules and place the PKG file.
> On a longer run the rules  will be maintained by a different team who prefer
> working only in DRL's and not in java files  . I did considering them to be
> access as Global variables but wheren't able to access in LHS. Hence
> reverted back to adding them in working memory.
>
> /declare RuleConstant
>    COUPE			: String = "C";
>    SEDAN			: String = "S";
> end/
>
> 2. We did consider having the Vehicle object as fact but there were
> requirements that required us to move back and forth a list of vehicles,
> like if a vehicle is < 2011 and previous vehicle is > 1999 where vehicles
> are ordered by purchase date compute X = Y. Though the below example doesn't
> show case this scenario.
>
>
>
> -----
> - Prashanth
> --
> View this message in context: http://drools.46999.n3.nabble.com/Abstracting-Rules-using-extends-tp4023217p4023219.html
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