Re: One-To-One Relationships
Date: Sun, 2 Dec 2007 05:16:46 -0800 (PST)
On 2 déc, 10:36, 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?
I am talking about neither of the two. If you ask me, I place terms like *entity* on the same level than terms like *object*: too subjective to be reliable to build logical reasonning onto. However, for the sake of discussion, I am trying to range relational bias aside to give a chance to ER modeling.
> -- Jan Hidders
Received on Sun Dec 02 2007 - 14:16:46 CET