Re: Objects and Relations

On Feb 23, 2:32 am, "David BL" <davi..._at_iinet.net.au> wrote:
> On Feb 22, 10:32 pm, "Walt" <wami..._at_verizon.net> wrote:
>
>
>
> > "JOG" <j..._at_cs.nott.ac.uk> wrote in message
>
> >news:1172092159.136958.258750_at_m58g2000cwm.googlegroups.com...
>
> > > On Feb 20, 2:18 pm, "David BL" <davi..._at_iinet.net.au> wrote:
> > > > [snip]
> > > > I still think we have a quite different understanding of what (in
> > > > practical terms) we mean by "entity". I think you're still
> > > > associating it with ERMs (even if you distinguish instance from type)
> > > > while I'm not. Let me explain what I mean by that...
>
> > > > You question whether written papers have an authors property or vice
> > > > versa. For me that question only arises at the point where you try
> > > > to create an ERM.
>
> > > Well yes I do see that. But I /don't/ think those issues start at the
> > > ERM, so I'm more than happy to address things outside the E/RM, at a
> > > 'real world' level (apologetic quotes for obvious reasons).
>
> > I'm a little confused by this. Perhaps I'd better explain what I use ERM
> > for. I use it for talking with subject matter experts about the data.
> > Subject matter experts never see the subject matter (aka universe of
> > discoure) as one vast amorphous blob of reality. They always see the
> > subject matter as made up of "things" and "associations among things".
>
> It would be useful if you could qualify whether you mean instances or
> types.
>
> > The word "entity" is just a fancy word for "thing". It has some advantages
> > over "thing". One of them is that if you call a person a "thing", some
> > people will be offended. If you call a person an "entity", no one will be
> > offended. The word "relationship" for "association" ias a little more
> > troublesome. In the RM, "relation" is used for mathematical relations
> > which are thought of, outside the area of data management, as ordered
> > tuples. "relationship" is a word that is used in the RM to describe
> > something very much like a relation, except that the components of the
> > tuples are referenced by name, and not by position.
>
> I thought the RM community had hijacked the word "relation" for their
> own purposes (ie for where a tuple is a map from attribute to value).
RM theory uses *relation* in its primal mathematical sense not in a general common sense. To RM advocates, a relation is not a *relationship* synonym but a precise concept defined in mahematical set theory and applied in computing.
Hope this clarifies further terminology issues... Received on Fri Feb 23 2007 - 09:57:59 CET