How to Build a Business Rules Engine

Introducing Rule Versions

The next major piece of functionality that has to be added to the Business Rules

Repository is needed to deal with rule versions.

Design for Rule Versions

What is different about the Screen Fields Valid Ranges rule type is that it is possible

for it to have different versions across time. The rule types discussed earlier could either

be implemented or not. The error messages and metadata about these rules could be

changed over time, but not the fundamental logic of each rule itself. The Screen Fields

Valid Ranges rule type can, in theory, be changed across time so that the ranges are

different. For instance, for the first year in which the sample application is imple-

mented, values in Investment Funding Date may not be allowed ...