Re: Lucid statement of the MV vs RM position?

Jon Heggland wrote:
>
> I focus on the significant difference between
>
> 1. An aggregate operator
> 2. The invocation of an aggregate operator within a SUMMARIZE operator
>
> You don't get from relation (1) to relation (2) in my post to Marshall
> just by using SUM. You have to use SUMMARIZE as well.

I agree, however I consider this point so obvious as to be not worth mentioning. No one bothers to distinguish carefully between, say, a function literal and an application of that function in speech. It's just quite clear from context.

There are quite a number of different programming models or functional programming languages that support "fold" or "reduce". (D&D here again making up their own terminology when perfectly good decades-old terms exist, confusing the discussion.) Only SQL and TutD, that I'm aware of, bother to have a separate abstraction called an "aggregate function." There really is no useful difference between SUM and +, or anyway between the pair (+,0). (In fact, most programming languages with fold put the identity element with the application of fold rather than with the folded function. In the math books I've read it seems that a function and its identity element are considered ineffeably bound.)

Marshall Received on Mon May 08 2006 - 16:20:28 CEST