Re: Normalizing the ER model

"Jan Hidders" <hidders_at_REMOVE.THIS.uia.ua.ac.be> wrote in message news:3df142a5$1_at_news.uia.ac.be...
> Greg Boland wrote:
> >
> >I like ORM because of the contraints one can apply to relationships.
>
> Good. I like ORM because it has a good linguistic and philosophical
> foundation and its semantics are formally described. :-)
>
> >But in my experience, these constraints are usually implemented by stored
> >procedures or some other procedural logic. So what does normalization
have
> >to do with it?
>
> A fact type is a relation so all of normalization theory applies to it
> directly. For example if you have a fact type with the roles Street,
Number,
> City and Zipcode then it is not in BCNF if Zipcode only determines Street
> and City. However, AFAIK there is no graphical notation for functional (or
> other) dependencies in ORM.
>
> -- Jan Hidders

Jan,

I agree, and you stated my point. What I'm saying (or attempted to say) that ORM relationship constraints cannot be implemented in the relational model . The fact type is simply a relation, and no constraints(except for cardinality) can be applied to it. So I still contend that normalization for the fact type does not enforce constraints.

Greg Received on Sat Dec 07 2002 - 02:22:06 CET