# Re: c.d.theory glossary (repost)

Date: Thu, 13 May 2004 22:36:11 -0500

Message-ID: <c81ern$kic$1_at_news.netins.net>

"Gene Wirchenko" <genew_at_mail.ocis.net> wrote in message
news:l338a0tlq4mrsdi31bg2tfbg1sdbn1ch5h_at_4ax.com...

> mAsterdam <mAsterdam_at_vrijdag.org> wrote:

*>
**> >Eric Kaun wrote:
**> >
**> >...
**> >> Ugh, can't find it - gone from my newsgroups.
**> >
**> >--------------- Do I contradict myself?
**> >Glossary 0.0.2: Very well then I contradict myself;
**> >may 5, 2004 I am large, I contain multitudes.
**> >--------------- -- Walt Whitman
**> >
**> >Preamble:
**> >---------------
**> >This glossary seeks to limit lengthy misunderstandings in
**> >comp.database.theory.
**>
**> It would help if it were more plainly written. I have been using
**> databases for quite a while, but I would like to learn more theory.
**> Some of the definitions here are rather obtuse. Examples follow:
**>
**> [snip]
**>
**> >[Class]
**> >A class is what provides a name and a place for
**> >the abstract behavior of a set of objects
**> >said to belong to the class. (Larry Wall, Apocalypse 12)
**>
**> I am glad that I already know what a class is.
*

Agreed. I've contested this definition a couple of times, but I don't have one that I think might pass a cdt test. I really, really don't like the "what" at the start. Find your favorite def of class and contribute it -- at the very least we could have an a. & b def of it.

*>
**> [snip]
**>
*

> >[Domain]

*> >Given a relation R, a domain is a set Sn such that for each tuple (A1,
**> >A2, ...An, ...Am) in R, An is an element of Sn.
**>
**> Huh?
*

> [snip]

*>
**> >[NULL]
**> >The insanity bit. No! The humility marker.
**> >mu: The absence of an answer to a question which requires an answer.
**>
**> Cute, but not of much practical help.
*

This exercise is new on the list -- notice the version number. So, jump in and help out and let's make it better.

*> [snip]
**>
*

> >[Relation]

*> >A relation is a subset of the set of ordered tuples (A1, A2, ... Am)
**> >formed by the Cartesian cross-product of sets S1 x ... x Sm where each
**> >An is an element of Sn.
**>
**> Huh?
*

That one was my contribution (as with function and domain, IIRC) and is the mathematical definition since there are many on this list who like precision (I among them, at times). Do you have another you would like to add for a list of valid defs of "relation"?

--dawn Received on Fri May 14 2004 - 05:36:11 CEST