Re: One-To-One Relationships
Date: Fri, 30 Nov 2007 19:51:21 GMT
Message-ID: <ZQZ3j.26$Uy.25_at_trndny07>
"paul c" <toledobythesea_at_ooyah.ac> wrote in message
news:Q9Z3j.8332$UQ1.1468_at_pd7urf1no...
> David Cressey wrote:
> >
> > Note that "attributes, values, and domains" are common elements to the
ER
> > model and to the relational model. They provide a brdige from one kind
of
> > modeling to the other.
>
> Of course people in different camps of any field will sometimes adopt
> the other side's lingo and call it their own, it's rampant among nations
> today. But attributes, values and domains aren't logical RM terms
> because they are "logical" nor because "they can be seen to exist" nor
> because they offer a bridge to some other theory but because they are
> necessary to define that model's operation.
The terms are not common because they are a bridge. They are a bridge because they are common. When Chen devised ER, and when I learned ER, it wasn't as a member of some "camp" or another. AFAIK, Chen never held that ER was a substitute for relational modeling. Rather, ER was a useful way ot look at the data, while leaving open the door to implementing in a relational system or some other kind of system (at the time network or hierarchical, which I kinda glossed over as CODASYL).