Re: Lucid statement of the MV vs RM position?

"Jon Heggland" <jon.heggland_at_idi.ntnu.no> wrote in message news:e3s29k$t38$1_at_orkan.itea.ntnu.no...
> David Cressey wrote:
> > At first you said that SUMMARIZE is not an aggregate operator. Then you
say
> > it produces a relation. Did you not intend to imply that the fact that
it
> > produces a relation was relevant to its not being an aggregate operator?
>
> No, just that it was relevant to its not being the aggregate operator
> SUM. I'm trying to draw an analogy: If you call the "operator"
>
> SUMMARIZE R BY { X } ADD (UNION(RELATION{TUPLE{Y Z}}) AS W
>
> an aggregate operator---call it GROUP---then you must for consistency
> also call the "operator"
>
> SUMMARIZE R BY { X } ADD (SUM(Y) AS Z)
>
> an aggregate operator---and it seems you must also call it SUM (what
> else?). Which for one thing is a significant departure from Bob's own
> definition of an aggregate operator, because there is a *lot* more than
> iterated addition going on in the above expression. It also begs the
> question what manner of beast the "SUM(Y)" expression that's part of it
> denotes---is that *also* the aggregate operator SUM?
>
> To return to you question, the definition of the aggregate operator SUM
> implies that it results in a number. Thus, the SUMMARIZE expression
> above that uses SUM cannot be the aggregate operator SUM, because (among
> other reasons) it results in a relation.*
>
> Thus, the only recourse left if you don't accept my claim that GROUP
> (and by extension, SUMMARIZE...SUM) isn't an aggregate operator, is to
> use the term "aggregate operator" for *both* an iterated operation (as
> in Bob's definition) *and* the use an iterated operation (but presumably
> just one at a time!) as a term in a SUMMARIZE expression. And I don't
> understand why anyone would want to do this.
> --
> Jon
>
> *On the other hand, the aggregate operator UNION, defined as iterated
> union (of relations), is an aggregate operator that *does* result in a
> relation, so that argument isn't as obvious for GROUP.

Thanks for clearing that up. Received on Wed May 10 2006 - 13:20:48 CEST