1. A method of integrating one or more declarative rules into a plurality of procedural instructions in a procedural computational system, the method comprising the steps of: executing, on a digital data processing system that comprises one or more digital data processors, a procedural sequence that comprises a plurality of procedural instructions, updating, upon execution of a procedural instruction that causes change to one or more variables, one or more other variables participating in one or more declarative rules so as to maintain relationships imposed by said one or more rules among said variables, wherein said one or more other variables are those not changed by the execution of that procedural instruction, and wherein said rules are defined outside that procedural instruction, and wherein said updating of said one or more other variables is performed by executing said rules on said digital data processing system prior to execution of any other procedural instruction in the sequence.