Re: Logical equivalence of simple and complex types under the relational model?

Rene de Visser wrote:
> I have read a number of papers that discuss whether complex data types
> should be allowed under the relational model.
>
> What I haven't seen analysed is whether there is actually any logical
> difference (upto renaming/isomorphism) between the resulting models.
>
> It seems to me at first sight that
>
> 1) RM with simple types
> 2) RM with complex types
>
> are indistiguishable at the logical level.

I agree with you that they are logically indistinguishable.

Where I think the question arises is when the relational system isn't kept totally separate from the type system, so you move away from the standard relational model to something else. For example, if you allow relation-valued attributes, but instead of handling them within the type system, you allow the relational system to directly access the values inside those internal relations.

Paul. Received on Tue Nov 30 2004 - 13:14:57 CET