When most people think of business rules, they tend to think in terms of big collections of IF-THEN-ELSE statements. You see the same kinds of questions and statements from vendors, customers and consultants about the same, simple kinds of rules, that you start to think of all business rules in simple terms like:
IF the car is a subcompact AND the customer is not a loser
THEN apply the discount
ELSE warn the agent
If all you do is write these sorts of simple-minded rules, you’re likely under utilizing your BRE. Most BRE’s (but not all!) allow you to write conditions using full First Order Logic. Specifically, you can write statements like "IF all of the cars on the lot are damaged THEN send an alert to headquarters" or "IF the patient has had at least three surgeries in the last 2 years THEN notify the primary care provider." The power lies in the availability of the Universal ("something is true for all items") and Existential ("there exists", or "there are at least 5 instances of") quantifiers. Not only do these quantifiers make it easier for you to write certain rules, they are baked into the RETE algorithm and thus will perform much better than workarounds you might build into your rule set.
Make sure to check that any rule engine you are considering includes support for these quantifiers. They are some of the more difficult parts of the RETE algorithm to get right and many commercial vendors don’t include them.
