Re: Undefinedness

From: paul c <>
Date: Thu, 22 Nov 2007 17:59:43 GMT
Message-ID: <jsj1j.20824$PE.17773_at_pd7urf1no>

JOG wrote:
> While I was only really concerned about whether my logic statements
> are sticking to 2VL internally, you've sent me off at a tangent here
> because CWA is one of my bugbears. Imho its at best silly, and at
> worst contradictory. Take relations such as:
> Weather_is = { condition: Hot }
> Weather_is_not = { condition: Cold }
> Domain = {Hot, Cold}
> Perfectly fine with full information, and a constraint that a
> condition can't appear in both. And I can happily extrapolate from CWA
> from the first relation that: !is(condition:cold)), and from the
> second !is_not(condition:hot). Nice...
> ...until we're faced missing information. If both relations are empty
> (because we just don't have the data say), then CWA tells me that:
> !Weather_is(condition:Hot) and !Weather_is_not(condition:Hot). It is
> both hot and not hot. Genius. I don't see how CWA based directly on
> what propositions state can ever be justified for a system working in
> the real world (TM).
> ...

Wait a minute. Regarding "weather_is", its complement is (!Weather_is(condition:hot)) AND ((!Weather_is(condition:cold)). This is not the same as just !Weather_is(condition:hot).

Similarly for Weather_is_not. Received on Thu Nov 22 2007 - 18:59:43 CET

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