Re: The Theoretical Foundations of the Relational Model

In article <3d1736a2.2083746_at_news.verizon.net>, JRStern <JXSternChangeX2R_at_gte.net> wrote:
>
>What we have here is a sign that in doing something with the database, we
>may be doing something which is not entirely equivalent to predicate logic.
>In some cases, the "easy" way to do stuff would be to specify a logical or
>physical order as part of the data model (of views, perhaps of tables).

Er, a "physical order" in a logical/conceptual data model is an oxymoron.

Easy for the user, sure, and defining such a data model is not difficult at all. But can you give me a sound and complete axiomatization for this new type of logic? Can you give me a reasonably complete set of algebraic operators with lots of nice algebraic identities that allow me to do query optimizations? Do you have some nice results in descriptive complexity theory that tell me the complexity of several syntactically restricted subsets of your new logic?

• Jan Hidders