Using Rules in Object-Oriented Designs

System requirements often express some of the behavior of a domain model in the form of policies, constraints, invariants, and rules. Although an object-oriented approach helps with the design of this model, the implementation is often cluttered with details necessary to enforce the model's policies and constraints. As a result, the code is more prone to error and is more difficult to maintain since it tends to obscure the model’s fundamental structure. R++, a rule-based extension to C++, allows developers to express policies and constraints more clearly in the form of path-based rules. Since the rule evaluation mechanism is automatic, R++ rules enable developers to focus on what to do when a rule evaluates to TRUE, rather than on how and when these evaluations should be carried out. It is the absence of this mechanism in the source code, and the use of these rules in an object-oriented implementation that makes the code easier to maintain and makes for a clearer reflection of the underlying model. Category: Experience Report Contact: Anil Mishra, room 2C-053 AT&T Network & Computing Services 480 Red Hill Road Middletown, NJ 07748 email: [email protected] phone: (908) 615-4552 fax: (908) 615-5579