Re: Lucid statement of the MV vs RM position?

paul c wrote:
> BTW, I did have in mind as you probably suspect that {S#, {P#}} was
> "all-key". When I first read about GUNF, I seem to remember my quibble
> was the inclusion of 'normal form' in the term. Admittedly, a better
> mind than mine thought it up but at what seems to me to be a preliminary
> point, I'd rather label it temporarily as group-ungroup equivalence or
> somesuch.

Fine by me. I don't really know what "normal form" means anyway. :)

> I say preliminary because at least for me ttm's group and
> ungroup examples seem to operate on one rva at a time and I wasn't sure
> what happens when more than one rva is involved and whether that might
> have something to do with the typical examples of multi-valued
> dependencies

That's an interesting thought---a MVD is what occurs when you ungroup two (independent) RVAs in some relation? Are the grouped and the ungrouped relations equivalent? Does the grouped variant exhibit anomalies equivalent or analog to those associated with MVDs?

> (group and ungroup seem to always imply a key, possibly a
> different one from the input relvar's key and this seemed a little
> chicken and egg to me).

I don't understand this.

> Plus, I wondered whether there's anything
> canonical/axiomatical that can be said about the results of specifying
> all or none of the attributes in a group or ungroup expression.

Uh... If you group all the attributes in a relation, you get a relation with a single attribute (the type of which is the same as of the original relation) and a single tuple (containing the original relation)? I'll have to read up on the latest GROUP/UNGROUP definitions.

> Perhaps my troubles here are just the result of misconceptions but I'm
> tempted to go even further and wonder if the concept of relvars is even
> necessary to discuss the subject of rva's, eg., when are two relations,
> written down differently, the same?

Huh? I though that was very clear.

> I know that to put it loosely, ttm
> says they are the same when they have the same value,

When they ARE the same value.

> so the relation of
> 'integer 3' doesn't have the same value as the relation of 'integer 6
> divided by integer 2' as far as the system is concerned

I don't understand this---please use more standard notation if you want to denote relations---but I think you are wrong. The integer denoted by the expression "6/2" is the same as the one denoted by "3". Of course, the system must be able to evaluate the expression "6/2" for the comparison to make any sense.

> (I didn't try to pursue this with the ttm people because that would seem
> like either ignorance or insolence to me, questioning ttm's starting
> points without having a systematic replacement for it whereas ignorance
> is tolerated here, at least up to a point, by more knowledgeable people
> such as you. Maybe I've reached that point!)

Heh. Yes, I also find TTM list more intimidating; I have never posted anything except complaints about quoting. :) I'd say there are people more ignorant than you posting there, though.

-- 
Jon