How to Build a Business Rules Engine

ical name. Thus, it becomes possible to create a rule type definition screen that cal-

culates one subtotal on one report and that can determine whether any other rule

exists that targets the same subtotal on the same report.

Of course, rule type definition screens for calculations and derivations should

ensure that users cannot actually define multiple rules within what should be one

rule. There is always a temptation to create rule definition interfaces that permit very

complex logic to be entered. The danger is that this complex logic actually includes

intermediate results that need to be stored and reused somewhere else. Such inter-

mediate results should be broken out into additional rules, or atomicity of business

rules is surely being violated. ...