Re: A question for Mr. Celko

On Fri, 16 Jul 2004 20:35:33 -0700, John Jacob wrote:

> I was browsing through the archives and found this gem, which remains
> unanswered. I for one would very much like to know what you are
> referring to, and why the solutions proposed in the book are "weird"

Joe Celko said that? Interesting, because I usually get the same reaction when talking to colleagues of mine that actually do research in the field of temporal databases.

One criticism I heard is that to simulate the PACK and UNPACK operators you have to use operators that violate 1NF as it is usually understood. But note that the exact definition of 1NF is not as well-understood as one might suppose. Chris Date, for example, apparently has decided to trivialize the notion.

Another criticism is that an algebraic approach is taken but one where the operators are not supposed to be implemented as such or where it would at least be impractical to do so. That deviates somewhat from the usual pattern. A calculus/logic-based approach would probably have been more appropriate here.

> The domain of integers is infinite, but we are quite content to model it
> with a finite set. In what way is this different?

If you mean "implement it" by "model it" then, yes, you are right. But we are talking about a logical data model, not an implementation model, so why then not model it as the infinite set that it really is?

> This is quite different from Rick Snodgrass's approach, which requires
> such Information Principle violating notions as hidden columns.

If those hidden columns can be made visible I don't see why this would be such a big problem. After all, the "information principle" is not some religious dogma but just a well-established well-tested and well-argued engineering principle.

• Jan Hidders