From: James Edward Gray II <james@...>
Date: 2005-07-04T00:35:43+09:00
Subject: Re: [QUIZ] Inference Engine (#37)

On Jul 3, 2005, at 8:24 AM, Pit Capitain wrote:

> Ruby Quiz schrieb:
>
>> This week's Ruby Quiz is to build an inference engine that is  
>> capable of
>> answering questions based on the provided truths.
>> ...
>>
>
> Just out of curiosity, after entering
>
>   > All Foos are Bars
>   OK.
>
> what should be the response to
>
>   > No Foos are Bars

Basically, whatever you are comfortable with.

> If the answer is "OK." it would mean that the set of "Foos" is  
> empty, because no Foo can be a Bar and not be a Bar. Questions like
>
>   > Are all Foos <whatever>?
>
> should then be answered with Yes.

This is the correct logical interpretations, but...

> The other alternative would be to assume that when speaking of  
> "Foos" the set of "Foos" isn't empty and there exists at least one  
> Foo?

This makes more sense to me, so it's probably what I would choose.   
Given that, I would likely just print an error message to the user,  
in the example you give.

James Edward Gray II