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.
(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.
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?)
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."
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