Re: Clean Object Class Design -- What is it?

"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 Sat Jul 21 2001 - 18:34:40 CDT