Re: Clean Object Class Design -- What is it?
From: Rico <TrooperRico_at_bugplanet.com>
Date: Sat, 21 Jul 2001 23:34:40 GMT
Message-ID: <gNJ17.1731$G42.3286_at_newsfeed.slurp.net>
Date: Sat, 21 Jul 2001 23:34:40 GMT
Message-ID: <gNJ17.1731$G42.3286_at_newsfeed.slurp.net>
"peter_douglass" <baisly_at_gis.net> wrote in message
news:9i7n3i$ju0$1_at_taliesin.netcom.net.uk...
>
> Rico wrote in message ...
>
> >"Set-level operations" have nothing to do with updating information.
> >"Set-level operations" are: union, intersection, difference, etc.
There's
> >no "update" in there.
>
>
> insert(x,S) = union (S, {x])
>
> remove(x,S) = difference(S, {x})
>
> update(x,y,S) = insert(y, remove(x,S) )
>
Ouch, completely obvious and I missed it. Relational algebra 101 and I blew it utterly. I stand corrected.
> --PeterD
>
>
Received on Sun Jul 22 2001 - 01:34:40 CEST