Re: Entity and Identity

On Jul 22, 11:53 pm, paul c <toledobythe..._at_oohay.ac> wrote:
> Nilone wrote:
>
> ...
>
> > Yes, that's what I was looking for.  Function composition is join, and
> > then function application would be selection, right?  The domain of
> > the function is the propositional condition that restricts the
> > selection, while the codomain would be the projection of the resulting
> > set of tuples.  Recursive queries would substitute the result set into
> > the the selection condition (of course they would have to be the same
> > type).  Recursively defined relations would produce infinite sets.
> > Any more references or information in this line?
>
> > I looked at some pages on relation algebra, but it's still beyond me,
> > I'll keep working at it, thanks for the info.
>
> See TTM Appendix A (pdf is online at ttm site) for concise explanations
> that reduce composition and selection to combinations of join and
> project, from a relational algebra viewpoint, it includes very tidy
> formal definitions.

Just read it, thanks. I'll have to get the book soon, I keep getting into things which have already been worked out.

BTW, I also came across the following article, which looks interesting:

RELATIONAL MODEL FOR PROGRAM SEMANTICS
http://www.ohiolink.edu/etd/send-pdf.cgi/Punnam%20Pradeep%20Kumar.pdf?acc_num=kent1226606883 Received on Thu Jul 23 2009 - 01:32:46 CEST