Dynamic business rules engine for ruby on rails

Question

I have an application which will require a "dynamic business rules" engine. Some of the business rules changes very frequently. Some of then applies for a limited set of business accounts. For example: my customer have a process where they qualify stores, based on their size, number of the sales person, number of products, location, etc. But he manages different account, and each account give different "weights" to each attribute.

How do I implement this engine using Ruby? I know Java has drools, but I find drools annoying and complex. And I prefer not having to use JRuby...

Regards,

Rubem

Answer 1

If you're sure a rule engine is what you need, you will need to find one you can use in Ruby. A quick Google search brought up Rools (http://rools.rubyforge.org/) and Ruby Rules (http://xircles.codehaus.org/projects/ruby-rules). I'm not sure of the status of either project though. Using JRuby with Drools might be your best bet but then again, I'm a Java developer and a big Drools advocate. :)

Without knowing all the details, it's a little hard to say how that should be implemented. It also depends on how you want the rules to be updated. One approach is to write a collection of rules similar to this: "if a store exists with more than 50 sales people and the store hasn't had its weight updated to reflect that, then update the store's weight." However, in some way you could compare that to hardcoding.

A better approach might be to create Weight objects with criteria that need to be met for the weight to apply. Then you could write one rule that matches on both Weights and Stores: "if a Store exists that matches a Weight's criteria and the Store doesn't already have that Weight assigned to it, then add the Weigh to the Store." Then the business folks could just create and update Weights, possibly in a web front-ended database, instead of maintaining rules.