Type Inheritance and Relational Theory

Chapter 3

Types with Inheritance

Ruinous inheritance

—Gaius:The Institutes (c. 175 CE)

This chapter provides a preliminary overview of some of the basic ideas of our inheritance model, in order to pave the way for a much more complete treatment of the material in subsequent chapters. It’s based in part on Chapter 12 of the Manifesto book (i.e., Databases, Types, and the Relational Model: The Third Manifesto, by Hugh Darwen and myself, 3rd edition, Addison-Wesley, 2007).

As noted in Chapter 1, there’s no consensus in the community at large on a formal, rigorous, and abstract type inheritance model. In our work on The Third Manifesto, therefore, Darwen and I were more or less forced to develop an inheritance model of our own—and of course it’s that model that’s the principal subject of the present book. Moreover, we were, and still are, very serious about our work in connection with that model. As we wrote in the Manifesto book:

We would like this effort on our part not to be seen as just an academic exercise. Rather, we would like our proposal to be considered by the community at large as a serious contender for filling the gap alluded to above (i.e., as a candidate for the role that is “formal, rigorous, and abstract” and can be generally agreed upon by that “community at large”). We offer it here in that spirit.

As I said in Chapter 1, these remarks remain just as applicable today as they were when we first wrote them.

WHY INHERITANCE?

Why is this topic worth investigating in ...