Krishna Satya wrote:

Hi, I am a new user to Drools and having passed the first few days of reading and experimenting with the tool I am now looking to see how rule parameters can be externalized. And along those lines looking for patterns and best practices. I have searched through the user forums (maybe not submitting the right search critera) and through samples etc.

My query is from my intent that application should be decoupled from rules and the rules are decoupled from its parameters.

I am wondering if Decision tables is the recommended approach or externalizing/sourcing from Db recommended. Does the Business Service that interacts with the rule engine source the rule parameters and push it into working memory for the rule to pickup...or should the rule declaration be tightly coupled to its parameters.

For example (Quick Psudo code, not sure if I have made any syntactical errors):

rule "Fee Waive Rule"
    when
         clientRequest : Request(account.balance > 2000 )
    then
          clientRequest.setFee(0);
end

rule "Fee Apply Rule"
    when
         clientRequest : Request(account.balance < 2000 )
    then
         clientRequest.setFee(5);
end

In the example above what are the best ways to externalize and make available to the rule the account balance and fee parameters?

Create web based forms that generate the rules on save, use something like MVEL for rule generation. I also recommend you flatten your objects, using account.balance foeld a field constraint is not optimal.

Any guidance on patterns/best practices/examples would be much appreciated.

Regards.
- Krishna
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