Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

From: vc <>
Date: 7 Jul 2005 12:02:00 -0700
Message-ID: <>

Jan Hidders wrote:
> VC wrote:
> > "Jan Hidders" <> wrote in message
> > news:ZmWye.138790$
> >
> >>VC wrote:
> >>
> >>>>>So what's the difference between an object and a conceptual object ?
> >>>>
> >>>>A conceptual object is an object that is part of the universe of
> >>>>discourse that is under consideration.
> >>>
> >>> That's cool, but what I was resally asking was what the difference
> >>>between an "object" and the "conceptual object". What is the word
> >>>"conceptual" doing here ?
> >>
> >>?? You mean, apart from indicating that this particular object belongs the
> >>universe of discourse?
> >
> > I still do not undertsand. Let's assume we define the object as an element
> > belonging to a set.


> Ok. Let's call that set UoE, the universe of everything.

> > You are saying that a "conceptual object" belongs to a
> > universe of discourse, the universe being a synonym of a set, I hope. Now,
> > my question is really simple: do an "object" and a "conceptual object"
> > belong to different sets ?

> Yes, "object" belongs to UoE and "conceptual object" belongs to UoD, the
> universe of discourse, which is a subset of UoE.

  A universe of discourse is usually understood as everything being talked about in a given discussion. E.g. in math we can talk about a model or a structure consisting from an underlying set U along with some relations. The underlying set, then, would be called the universe of discourse. Now, everything else beyond the U.o.D is simply irrelevant, it does not exist as it were, so why even mention it and reserve a special word for it ("object" without any qualifier) ? When something else becomes relevant, then this "something", naturally, will be included in the U.o.D. To sum up, why cannot we talk about just "objects in the U.o.D" and need this "conceptual object" thingy ?



> -- Jan Hidders
Received on Thu Jul 07 2005 - 21:02:00 CEST

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