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Database in Depth by C.J. Date

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Chapter Eight. What Is the Relational Model?

You might think it odd for the final chapter in a book that's meant to explain the relational model to have as its title What Is the Relational Model? Aren't you supposed to know by now?

Well, yes, you are. But the point of this chapter is to serve as a kind of wrap-up for everything that's gone before; in particular, it's meant to give a precise definition, for purposes of future reference, of just what it is that constitutes the relational model. The trouble is, the definition I'll give is indeed precise: so precise, in fact, that I think it would have been pretty hard to understand if I'd given it in Chapter 1. (As Bertrand Russell once memorably said: Writing can be either readable or precise, but not at the same time.) Of course, I did give a definition in Chapter 1--a definition, that is, of what I there called "the original model"--but I frankly don't think that definition is even close to being good enough, for the following reasons among others:

  • For starters, it was much too long and rambling. (Well, that was fair enough, given the intent of that preliminary chapter, but now I want a definition that's succinct as well as precise.)

  • I don't really care for the idea that the model should be thought of as consisting of "structure plus integrity plus manipulation"; in some ways, in fact, I think it's actively misleading to think of it in such terms.

  • "The original model" included a few things I'm not too comfortable with: for instance, ...

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