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
Received on Sat Mar 04 2006 - 16:37:03 CST
