Re: Guessing?

From: Brian Selzer <brian_at_selzer-software.com>
Date: Tue, 8 Jul 2008 17:47:37 -0400
Message-ID: <_fRck.15052$N87.12329@nlpi068.nbdc.sbc.com>

"paul c" <toledobysea_at_ac.ooyah> wrote in message news:33Ock.59297$kx.264_at_pd7urf3no...
>
>> Brian Selzer wrote:
>> ...
>>> Consider the following statements:
>>>
>>> 1. Susan is an electrical engineer.
>>> 2. Susan is a mechanical engineer.
>>> 3. Susan is an electrical engineer or Susan is a mechanical engineer.
>>> ...
>
>
> I have another question. Suppose we have a database that involves only
> statement 3. Just what does its extension look like?
>

Correctly formed, each extension of the database would consist of two relations: one for mechanical engineers and one for electrical engineers. There are three possible extensions:

one where Susan is both an electrical engineer and a mechanical engineer,

MechanicalEngineers {{Person:Susan}}
ElectricalEngineers {{Person:Susan}};

one where Susan is not a mechanical engineer but is an electrical engineer,

MechanicalEngineers {}
ElectricalEngineers {{Person:Susan}};

and one where Susan is a mechanical engineer but is not an electrical engineer,

MechanicalEngineers {{Person:Susan}}
ElectricalEngineers {};

but only one of them represents what is actually the case. Received on Tue Jul 08 2008 - 16:47:37 CDT

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