Re: ANTISYMETRIC RELATIONS???

In article 214501U54778_at_uicvm.uic.edu, U54778_at_uicvm.uic.edu () writes:
>
> In an issue of Oracle magazine, dated Winter 1993, page 88, in an article
>by Hans J. Drucks named "Beyond the Relational Data Model", Mr. Druck refers
>several times to "antisymetrical relations". I know a little about
>relational theory. I know a little about object theory. Perhaps too little
>if this term does not fire any neurons in my brain.
> Considering the possibility that everyone knows what he is talking about
>and I am a rube from hodunk, have pity on me and please inform me of what
>is the meaning of this term.
> One can assume that he is talking about certain aspects of the object
>model as defined in a relational matrix. I just don't know of any
>descriptive usage that uses the term "symetrical" in relational which
>can then be
>turned around into "antisymetrical" when talking about object. I know
>someone will probably call me an idiot and ask just who am I and the
>donkey I road in on but have compassion and clue me in.
>
>ALAN ROGERS **** U54778_at_UICVM.UIC.EDU * I speak only for myself as a *
>VMKRAFT INC. 708-675-8615 * citizen of the UNIVERSE, not *
> * as an employee of Vmkraft nor*
> * as a user of U of I Services.*

I'll take a stab at it, although I am only working in the relational world part-time.

I suspect that the relations he is referring to are those between two entities in an Entity-Relationship-Diagram (ERD). As a simple example of a "Symmetrical" relation, we have two entities - CUSTOMER & ORDER. The relationship between these two might be "Customer places an order" and it's symmetrical inverse, "An Order is placed by a Customer".

In the ERD's that I have worked on, most relations are of this type - or perhaps more accurately, I make them this type unless there is a strong reason to specify anti-symmetrical relations. I can't think of a simple anti-symmetrical relation off the top of my head but most complex ERD's have several of them.

Tom Connolly

e-mail: connolly_at_udel.edu Received on Sun Jan 31 1993 - 13:31:00 CET