Here are some guidelines to identify areas where you can use a rule engine.
1. The number of business rules is large
2. Externalize only those rules that you expect will change often
3. Externalize only those rules which the business is interested in.
4. Business Rules Visibility is important .
5. Remember this! Validation rules are typically written, maintained by IT. With Business Rules on the other hand, you should aim to involve your business analysts in writing, managing and evolving them eventually
