Re: One-To-One Relationships

On 4 dec, 21:55, vldm10 <vld..._at_yahoo.com> wrote:
> On Dec 3, 6:01 am, Jan Hidders <hidd..._at_gmail.com> wrote:
>
>
>
> > On 2 dec, 18:53, vldm10 <vld..._at_yahoo.com> wrote:
>
> > > On Dec 2, 4:36 am, Jan Hidders <hidd..._at_gmail.com> wrote:
>
> > > > On 1 dec, 06:26, vldm10 <vld..._at_yahoo.com> wrote:
>
> > > > > On Nov 30, 9:34 am, Jan Hidders <hidd..._at_gmail.com> wrote:
>
> > > > > > Why by only one attribute? Why not by a set of attributes? Or a
> > > > > > combination of attributes and relationships (as is the case for weak
> > > > > > entities)?
>
> > > > > This is OK, but my advice to you -don't use it often.
> > > > > I will give you one example:
> > > > > The relation has A1, A2, A3, A4 "attributes" and they are mutually
> > > > > independent (i.e. they are in BCNF)
> > > > > The "attributes" can change their values for "entity" like in
> > > > > "temporal DB". User needs on line all information for any "entity" in
> > > > > any moment.
> > > > > Can you please write the key for this relation so that we can discuss
> > > > > it.
>
> > > > You do realize we were talking about ER modeling, not RM modeling,
> > > > don't you?
>
> > > Here in this tread it is about E/R and RM as well as relationship
> > > among them and I also used terms "entity" and "attribute".
>
> > My remark that you responded to was only about ER modelling.
>
> I tried to explain my answer through an example.

You formulated the explanation of your answer to an issue in ER modeling in RM terminology. If you would have formulated it in ER terminology that might have helped you considerably to make your point. RIght now I still don't have a clue what you are trying to tell me or even whether it is actually relevant for the question at hand.

• Jan Hidders