Re: Pizza Example

From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Wed, 14 Apr 2004 21:32:01 GMT
Message-ID: <l5ifc.71570$MG1.4809827@phobos.telenet-ops.be>

Eric Kaun wrote:
> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
> news:KVZec.70676$MG1.4809827_at_phobos.telenet-ops.be...

>>
>>So, one would expect that the NEST and UNNEST operators of the nested
>>relational algebra would not be allowed, wouldn't one?

>
> Do you mean GROUP? As far as I know, those are merely shorthand, not
> something new.

?? Are you saying that the GROUP / UNGROUP operators, as Date calls them, can be expressed with the operators of the flat relational algebra?

>>I know I would.
>>What else could "logically expose" mean for a relation-valued column?

>
> Operators on an attribute/column of type T are exposed, same as operators on
> any other type are exposed for use on values of that type. But one could
> certainly argue that the "nesting" in values/subvalues in Pick are simply
> exposed operators of a 2/3 level type. Hmmm. Mayhap I've argued myself into
> a corner. Or maybe it's just late.

Maybe. Maybe it's just Date. :-)

>>Ah, well, let me say here and now that I'm not a big fan of Chris Date,
>>to put it mildly, and the arrogance of dbdebunk makes me physically
>>sick.

>
> I can certainly see that, and I don't claim to be an expert - from what
> you've written, I'm fairly sure you're much more knowledgable than I on
> relational matters. But I find their site interesting, and useful as a
> bulwark against the wave of "novel" new data management techniques. While
> I'm not familiar with the "deep" research, I don't see much understanding of
> relational in common practice, and think it's certainly better than the ad
> hoc approaches being advocated.

I agree with all of the above, although I would add that the "is certainly better than" should be qualified. An RDBMS is not *always* under all circumstances certainly better. As much as I dislike dbdebunk and Date's tendency to speak to us ex-cathedra of all things relational, I consider myself very much in the "relational camp" and believe it has the best (scientific and non-scientific) arguments of them all. That's exactly why we don't need all this religious zealotry with the apparently necessary condescending attitude and oversimplifications.

Jan Hidders

Received on Wed Apr 14 2004 - 16:32:01 CDT