[Attempto] Should I allow for non-monotonic reasoning?

[Norbert E. Fuchs]

David

> On 11 Aug 2015, at 13:47 , David Whitten <whitten at netcom.com> wrote:
> 
> I don't know what I have done wrong.
> 
> I tried using the web interface for race, but don't know why (below) subset #1 (Mary) and set#2 (at least 1 woman) are included.
> I had the axiom set:
> 
> Every man is a human. Every woman is a human. 
> Mary is a human that is a woman. John is a human that is a man. Mack is a human.
> if a human is not provably a woman then the human is a man.

As it seems your axiom set contains some redundancy in axioms 1 and 4, and axioms 2 and 3. I would have written either

Every man is a human. Every woman is a human. 
Mary is a woman. John is a man. Mack is a human.
If a human is not provably a woman then the human is a man.

or somewhat less general

Mary is a human that is a woman. John is a human that is a man. Mack is a human.
If a human is not provably a woman then the human is a man.

But even with these simplifications you would not get the expected results. As it turns out RACE contains a bug: I did not apply some internal transformations to the negation-as-failure axioms that I apply to the other axioms. The is a result of adding the "odd fellow" negation-as-failure to an otherwise functioning system. I am working on this rather complex issue and will let you know when I will be done. Until that time I would like to thank you for exposing this bug.

> 
> I had the query:
> 
> ...

> I thought maybe I needed to say "man is a human" and "woman is a human" can't occur at the same time (or at least is abnormal) to exclude Subset #1 and Subset #2, but instead I get a syntax error:
> 
> Axiom Set:
> Every man is a human. Every woman is a human. 
> Mary is a human that is a woman. John is a human that is a man. Mack is a human.
> if a human is not provably a woman and the human is not provably a man then the human is a man.
> if a human is provably a woman and the human is provably a man then it is abnormal. 
> if a human is provably a man then the human is not a woman.
> if a human is provably a woman then the human is not a man.

The syntax error is not surprising since "is provably" does not exist in ACE since it is superfluous. There is no difference between "if a human is provably a woman" and "if a human is a woman".

Best regards.

   --- nef