Chapter 4 -- Implementing the Rules

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Chapter 4

Before we go into the implementation of our rules, let's get acquainted with the vocabulary of the subject area of the application. In our experience, one of the best ways of doing that is to take a look at (or develop) an entity relationship, or data, model of the subject area.

This is in contrast to the attitude of an advocate of pure object orientation. He or she would argue that a class model is better. Maybe, but that depends on the role you give the class model. We see the class model as an abstraction of a set of objects, the purpose of which is to bring services to their clients. We don't see these objects as holders of persistent data. In our opinion, holding persistent data is a job for the database. We don't even consider the holding of temporary data as a primary task for a business object. For us, a business object is primarily a service provider.

Now let's take a look at a part of the data model.