Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!lll-winken!cert!netnews.upenn.edu!grad2.cis.upenn.edu!aaron
From: aaron@grad2.cis.upenn.edu (Aaron Watters)
Newsgroups: comp.databases
Subject: Re: errors and 4-valued logic
Message-ID: <31123@netnews.upenn.edu>
Date: 12 Oct 90 19:47:46 GMT
References: <1602@meaddata.meaddata.com>
Sender: news@netnews.upenn.edu
Reply-To: aaron@grad1.cis.upenn.edu (Aaron Watters)
Distribution: comp
Organization: University of Pennsylvania
Lines: 36

>|> In response to my brief account of one variety of 4-valued logic
>|> where I claimed:
>|> 
>|> `the king of North America is bald' is error.

In article <1602@meaddata.meaddata.com> gordon@meaddata.com (Gordon Edwards) writes:
>
>I respectfully disgree with your disagreement. :-)  You treat the statement,
>"The king of North America is bald" as  having a single semantic.
>What you really have is:
>
>assertion :-
>	is_ruled_by(North_America, king),
>	is(king, bald).  /* read as pseudo prolog */

Not at all.  This is the statement `X is the king of North America
and X is bald.' which is false for all X.  Not at all equivalent to
the statement `The king of north america is bald.' which involves
no quantification.'  If we have a relation
  landmass(Name,Kingname,Kinghashair)
Then the entry for northamerica should read
  landmass(`north america', NOT_APPLICABLE, NOT_APPLICABLE)
and the answer to the question `what is the name of the king
of north america?' and `Is the king of north america bald?'
are both ILLFORMED QUERY or ERROR.


>|> 
>|> PS: I also claim that `I am green years old' can reasonably be
>|> treated as false.
>
>OK, I'll bite.  How?

I am 2 years old (for the sake of argument and privacy).
It is perfectly reasonable to say that
  `I am X years old' is false exactly when x=!2.		-aaron