Re: circular relationships ok?

Alexandr Savinov wrote:
>
> Notice that it has nothing to do with constraints imposed on data and
> implementing cycles indirectly. We still can impose any constraints just
> as in RM. The only difference is that we avoid cycles in referencing.
>

This is indeed the difference. In RM, foreign key references ARE constraints. There is no other type of reference in the model. Cyclical references are not implemented "indirectly" - In RM they are direct and explicit and are required for reasons of integrity. You still have the same cycles in constraints but you call them "indirect" for some reason.

--
David Portas