RE: ONT RE: Data Models, Ontologies, Logic
Matthew,
I will study what you say and maybe ask you some questions off list.
Thank you,
Jim
On Wed, 29 May 2002, West, Matthew R SITI-ITPSIE wrote:
>
> Dear Jim,
>
> You are confusing the language with what is said.
>
> See comments below.
>
>
> Matthew West
> Principal Consultant
> Shell Information Technology International Limited
> Shell Centre, London SE1 7NA, United Kingdom
>
> Tel: +44 20 7934 4490 Other Tel: +44 7796 336538
> Email: matthew.r.west@is.shell.com
> Internet: http://www.shell.com
>
>
> > -----Original Message-----
> > From: Jim Farrugia [mailto:jim@spatial.maine.edu]
> > Sent: 28 May 2002 22:12
> > To: West, Matthew R SITI-ITPSIE
> > Cc: Ontology
> > Subject: Re: ONT RE: Data Models, Ontologies, Logic
> >
> >
> > Matthew,
> >
> > Just a few brief comments below.
> >
> > Oh, and apologies for the strange formatting - I tried to line things
> > up in my mail editor, apparently without success. :-(
> >
> >
> > Jim
> >
> > ---------------------------------------------------------------------
> >
> > JA - Jon Awbrey
> > JF = Jim Farrugia
> > MW = Matthew West
> >
> > MW: > Dear Jim,
> > >
> > > The best definition I know of "data model" is "the structure and
> > > meaning of data". This is some distance from the ones you offer
> > > below. See below for specific comments.
> > ...
> >
> > JF:
> > > >
> > ---------------------------------------------------------------------
> > > >
> > > > "A data model is an abstract, self-contained,
> > logical definition
> > > > of the objects, operators, and so forth, that together
> > > > constitute
> > > > the abstract machine with which users interact. The
> > > > objects allow
> > > > us to model the structure of the data. The operators
> > > > allow us to model
> > > > its behavior."
> > > >
> > > > Source: An Introduction to Database Systems, Seventh Edition
> > > > by C. J. Date. Addison Wesley Longmann,
> > 2000, p. 14.
> > >
> >
> >
> > > MW: This seems to be how data is represented and processed,
> > rather than
> > > anything to do with a data model (aka entity-relationship model).
> >
> > JF: I would agree that the above definition seems to deal with how
> > data are represented. It doesn't seem to me, though, that it
> > deals with how
> > data are processed, if you mean processed by an actual implementation.
>
> MW: This is how I interpret operators and abstract machine.
> >
> > (In the same book, a few lines below the definition quoted above, is:
> > "An implementation of a given data model is a physical
> > realization on a
> > real machine of the components of the abstract machine that together
> > constitute the model.")
> >
> > I don't mean to suggest that Date's definition is gospel. But he is a
> > significant author in database-land, and his way of defining
> > the phrase "data models" is probably at least worth considering.
>
> MW: Two points.
>
> 1. Date is significant at the "language" level. I have never seen a large
> schema definition with his name on it. This is like the difference between
> being expert at FOL and expert at metaphysics.
>
> 2. Terms get meaning by usage, not definition. At most he is saying how he
> is using the term in this context. Don't expect anyone in database
> development
> land to have this understanding of the term.
> >
> > Also, I would like to suggest that maybe Matthew's "structure
> > and meaning of
> > data" really does show up in Date's definition, in the following ways.
> >
> > Matthew's definition deals with the structure and meaning of data.
> > Perhaps one could sensibly claim that the definitions of objects and
> > operators (from Date's definition) are a representation that
> > allows one to
> > model the structure of data, maybe something like the way
> > that molded clay
> > represents and models a chair?
> > (Is it possible to model the structure of data without
> > representations?)
>
> MW: Quite. Date is talking about the language. I am talking about what is
> said in the language. Therefore they are nto the same thing, but there is
> a relationship.
>
> >
> > And perhaps the meaning of the data is gotten at, at least
> > partially, by
> > the operations that can be defined on that data.
> >
> > I'm just guessing here, and trying to see if this way of understanding
> > Date's definition makes sense to Matthew.
> >
> > For my part, I'd be happy to see Matthew and Jon more or less
> > agree on a
> > definition that suits them, or come to feel that they each
> > know what the
> > other means by "data model."
>
> MW: It is just a matter of understanding that there are different usages,
> and who uses them for what purpose.
> >
> > I'm more interested in following these ideas back and forth
> > to see what
> > may come of this discussion than in trying to foist on you an
> > inappropriate
> > definition.
> >
> > I'll leave comments on the Vianu article for later.
> >
> >
> > Jim
> >
> >
>