Also adapt the language of your application to the language of the problem itself. Doing so will make communication with your end-user much easier. It will also insure that your constraints are relevant to the problem, and in the long run, it will make maintenance easier as well. Even more important, the natural structure of the problem domain can lead directly to good models for the application. By good models, in this context we mean compact, flexible, and understandable. Always stay close to the semantics of the problem. Yes, always.

An object-oriented approach distinguishes structural constraints (inherent in a class) from specific constraints (intrinsic to an instance). This distinction offers a powerful tool for organizing the constraints expressed by an end-user.

We recommend that you create the first model as closely as possible to the way the end-user initially formulated the problem.