How Many Rules?
Daryl Pereira 270002AW8D firstname.lastname@example.org | | Tags:  ilogdialog business rules
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(Guest post by Steve Núñez of Illation)
I’m always surprised when customers ask: “How many rules do we need?” and a surprising number of them do. That’s a bit like asking: “How many lines of code do I need?” The answer is, always, “It depends”. It depends on a lot of things, primarily the complexity of the problem domain and the object model.
Travellers insurance gave an example that illustrates a typical ramp up in the number of business rules. Their initial implementation had 20K rules, a number not unusual for the insurance industry. Today, they have 40K, and are building capacity for 200K.
One attendee asked “How did you get from 20K to 40K rules”. The answer was, essentially, that they initially implemented a model that assigned the same risk to large segments of the population. Over time, their actuaries discovered additional risk factors and refined their model, leading to 40K rules.
So, the more fine-grained the risk model, the greater the number of rules. Seems obvious, but it’s an often missed point. The other lesson to take away from this example is that they can implement such a fine-grained model. Managing this number of rules in a traditional programming language would be difficult, if not impossible.
- Steve Nunez, Principal Consultant for BRMS, Illation Pty Ltd (Australia)