Re: Lucid statement of the MV vs RM position?
From: Jon Heggland <jon.heggland_at_idi.ntnu.no>
Date: Sat, 06 May 2006 13:42:29 +0200
Message-ID: <e3i233$7h4$1_at_orkan.itea.ntnu.no>
>
> To expand:
>
> GROUP : UNION :: SUM : +
>
> GROUP is to UNION as SUM is to PLUS.
Date: Sat, 06 May 2006 13:42:29 +0200
Message-ID: <e3i233$7h4$1_at_orkan.itea.ntnu.no>
Marshall Spight wrote:
> Marshall Spight wrote:
>> Isn't GROUP an aggregate operator?
>
> To expand:
>
> GROUP : UNION :: SUM : +
>
> GROUP is to UNION as SUM is to PLUS.
I don't agree completely. UNION is a set operator; the individual values that you group in a GROUP operation aren't sets. But since I don't fully accept GROUP being an aggregate operator, I won't/can't explore this further.
> Interestingly, UNION is parametrically polymorphic, which
> raises the issue of parametrically polymorphic aggregate
> operators.
Isn't SUM also? It works on both integers and rationals; perhaps even dates.
BTW, TTM defines UNION and INTERSECT aggregate operators. They work on relations (RVAs).
-- JonReceived on Sat May 06 2006 - 13:42:29 CEST