SQL and Relational Theory, 2nd Edition

THE RELATIONAL MODEL vs. OTHERS

Perhaps you can begin to see now why it’s my opinion that (to repeat something I said in Chapter 5) the relational model is rock solid, and “right,” and will endure. A hundred years from now, I fully expect database systems still to be based on Codd’s relational model. Why? Because the foundations of that model—namely, set theory and predicate logic—are themselves rock solid in turn. Elements of predicate logic in particular go back well over 2,000 years, at least as far as Aristotle (384-322 BCE).

So what about other data models?—the “object oriented model,” for example, or the “hierarchic model,” or the CODASYL “network model,” or the “semistructured model”? In my view, these other models are just not in the same ballpark. Indeed, I seriously question whether they deserve to be called models at all.^[174] The hierarchic and network models in particular never really existed in the first place!—as abstract models, I mean, preceding any implementations. Instead, they were invented after the fact; that is, hierarchic and network products were built first, and the corresponding models were defined afterward, by a process of induction—here just a polite term for guesswork—from those products. As for the object oriented and semistructured models, it’s entirely possible that the same criticism applies; I suspect it does, but it’s hard to be sure. One problem is that there doesn’t seem to be any consensus on what those models might consist of.^[175] It certainly ...