Re: [ontolog-forum] Executable English and Logic (Was: accounting inteop

["Adrian Walker" <adriandwalker@xxxxxxxxx>]

Pat --

You can probably answer this off the top of your head.  

Is it correct to say that the model theoretic semantics of the following are compatible?

(1) Datalog extended with NAF 

          (Minimal model, stratified)

(2) Classical first order logic.

I think it's often loosely stated that Datalog + NAF is a subset of FOL, but that refers to syntax, and only holds if you -- dangerously -- use the same sign for negation in both.

                                   Cheers,  -- Adrian

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Adrian Walker
Reengineering

On Sun, May 11, 2008 at 9:51 AM, Pat Hayes <phayes@xxxxxxx> wrote:

At 10:26 PM -0400 5/10/08, John F. Sowa wrote:
>Adrian,

>
>  > Unfortunately, classical logic assigns a meaning to negation
>  > that differs from the way databases are actually used.
>
>That is true.  There are four widely used options:
>
>   1. The closed-world assumption (CWA) in which any ground clause
>      (n-tuple of constants) not asserted to be true is assumed
>      to be false.  This is typical of airline reservations:  if
>      your reservation is not in the DB, you don't have one.
>
>   2. The open-world assumption (OWA) in which any ground clause
>      not asserted to be true has an unknown truth value.  This
>      is typical of most databases generated from observations.
>      Anything not observed is not known to be true or false.
>
>   3. Three-valued logic (TVL) in which some ground clauses are
>      asserted to be true, others are asserted to be false, and
>      any others have an unknown truth value.
>
>   4. The whatever assumption (WA) in which anything not asserted
>      to be true may be false, unknown, or whatever.  This is the
>      widely used method of code-and-debug until you get tired
>      or the deadline has passed.
>
>

>  > Unfortunately, classical logic assigns a meaning to negation
>  > that differs from the way databases are actually used.
>
>Classical negation corresponds to the CWA.

I think you mean the OWA.

Pat
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