Ultimately I guess the decision is yours, as you possess the domain knowledge.
In your example, if the amount 2000 is static you could externalise this into a global; if however it is dependant upon another domain entity (ClientType for example) you might introduce it as another Fact.
You could also look into externalising by using the "from" keyword (although the result needs to be static as the rule engine cranks).
My preference, if the parameters are static, would be for the use of globals read by the service tier and put into the WM.
With kind regards,

From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Krishna Satya
Sent: 12 December 2007 15:10
To: rules-users@lists.jboss.org
Subject: [rules-users] Externalizing Rule parameters - patterns/bestpractices

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"
         clientRequest : Request(account.balance > 2000 )

rule "Fee Apply Rule"
         clientRequest : Request(account.balance < 2000 )

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

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

- Krishna