Re: RM formalism supporting partial information

From: Marshall <>
Date: Mon, 19 Nov 2007 19:10:57 -0800 (PST)
Message-ID: <>

On Nov 19, 3:35 pm, paul c <> wrote:
> Marshall wrote:
> ...
> >> The important concepts are tuples, propositions, predicates etc.
> > For myself, I have found less and less use for the concept
> > of tuple over time. I try as much as possible to do everything
> > with just relations. Relations as sets-of-propositions, relations
> > as predicates, cardinality-1 relations instead of tuples, etc.
> > In fact I am going so far as to attempt the idea of a theory with
> > relations as the only primitive. (And possibly also including
> > scalars.)
> > Not 100% clear if the idea can be carried out all the way, but
> > it's promising so far.
> (Forgot to ask this before). I notice that D&D depend on tuples to
> define their GROUP operator. Is there a way to define a Grouping or
> group-by operator with tuples?

Um, I forget: their GROUP is not the same thing as SQL group-by, right?

I don't have a well-thought-out answer, but my general approach to anything
not plain-vanilla RA operators has been to do them with user-defined (or library) aggregates.

Marshall Received on Tue Nov 20 2007 - 04:10:57 CET

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