Re: circular relationships ok?

Alexandr Savinov wrote:
>
> Customer Product
> \ /
> Favorite(c,p)
>
> Now we can get a list of favorite products for a customer and a list of
> customer for this product as a favorite.
>

But now you've removed Order from and Item from the diagram. Are you saying you can only avoid loops by drawing 2 diagrams instead of 1?

> I do not see in your SQL example circular references.

Then you didn't draw the ER diagram for the constraints in that schema.

>
> > Can "concept oriented" enforce such constraints?
> > If so, how do you draw diagrams of them without loops?
>
> A model with cycles is not a concept-oriented model (theoretically). It
> is a strong constraint but it is part of the definition. Then the
> question is if it is useful or not.

I think that means No. You are saying I have to change my business rules for concept-oriented to work?

--
David Portas