Re: Objects and Relations

On Feb 16, 4:04 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> JOG wrote:
> > On Feb 16, 4:40 am, Joe Thurbon <use..._at_thurbon.com> wrote:
>
> >>David BL wrote:
>
> >>[...]
>
> >>PMFJI, but I think there is an essentially definitional misunderstanding
> >>here. Although, you know, I'm only new at this, so take it with a grain
> >>of salt. I'm really interrupting to see if I'm getting a better
> >>understanding of all this, and I do so with some trepidation.
>
> >>The word that I think is being used extremely loosely is 'entity'.
>
> >>In your post you use it to describe, variously,
>
> >>- integers,
> >>- relations,
> >>- elements of any set,
> >>- things that we want to model with a relational theory*
>
> >>and a term that can be used to describe anything is basically useless.
>
> >>*BTW, I'm using theory here in the sense of a logical theory, i.e. a set
> >>of constants, functions, domains, etc. In this post, I'll not use theory
> >>in any other sense.
>
> >>I'm pretty sure that Jim is using 'entity' to describe 'things that we
> >>might agree exist in the real world', or at least, things outside the
> >>relational theory at hand. An in particular, I think that things that
> >>exist within the theory are not entities, by definition.
>
> >>Although Jim should feel free to correct me if I'm putting words into
> >>his mouth.
>
> > No you are pretty much on the money there imo Joe.
>
> > I am happy to put up with the definition of an entity describing a set
> > of attributes/value pairs. All I object to is the concept that these
> > sets are anything but arbitrary collections.
>
> > To some people a 'book' requires an attribute stating whether it is a
> > hardback or a softback. In other contexts a book might just be
> > composed of its title, its content, etc. (a book published online
> > perhaps). Please don't dwell on this example, it is just off the top
> > of my head to show that 'entities' are artifices and vary incredibly
> > from person to person and context to context. So as far as data
> > management is concerned, keep 'entities' out, and let humans resolve
> > such concepts outside of the logical model.
>
> If we have entities, then we have to accept that the book is nothing
> more than a property of the cover type entity.

well put indeed sir. Received on Fri Feb 16 2007 - 21:24:41 CET