Re: Modeling question...

On Oct 24, 12:23 am, paul c <toledobythe..._at_oohay.ac> wrote:
> David BL wrote:
>
> ...
>
> > I also find it rather telling that relational queries (ie RA
> > expressions) are not themselves represented using relations.
>
> Just because some syntax doesn't look like a relation doesn't mean that
> the result isn't defined by relations. Eg., the D&D relational operators
> are all defined in terms of relations, then a bunch of shorthands are
> given, so as to minimize tedium and clerical errors. SQL doesn't do
> this which may be why so many people who think it is obedient to the RM
> have such weird ideas, such as thinking a relation can be updated.
>
> Surely
>
> > if that were useful, many cdt folks would jump at the opportunity to
> > further promote the use of relations.
>
> A relation is a mathematical construction. How well implementations
> mimic it is very much in the mental "eye" of the beholder, in a way
> implementation is a misleading word for what is really just an
> mechanical aid for symbolic manipulation and storage of results.

Sorry I have no idea what you're getting at.

Let me be more specific: when you see a wff in some formal language, do you actually think of it as a relation? How is that useful? More specifically, how is the RA useful? Can you give me an example together with the relation's degree and the names and types of its attributes? Received on Fri Oct 24 2008 - 05:10:37 CEST