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expressing scope of negation of failure (wasRe: Open Worlds, Distribution, Delegation, Federation, Logic, NI )

From: Tim Berners-Lee <timbl@w3.org>
Date: Tue, 6 Mar 2001 23:25:19 -0500
Message-ID: <01fc01c0a6be$a0592e10$c1defea9@CREST>
To: <jos.deroo.jd@belgium.agfa.com>, "Sandro Hawke" <sandro@w3.org>
Cc: <www-rdf-logic@w3.org>, <www-rdf-interest@w3.org>

> My approach (not yet implemented) is much more explicit: conclude
> (instead of a literal) something like "this engine could not satisfy
> this proof", which I can't think of how to express in n3 right now.
> "This engine" is an identifier for the running process which tried to
> find the proof, and "this proof" is an identifier for the proof
> requested.  or something like that.

This requires a model of the knowledge  in the engine at a given time.
I was thinking along the lines of

followsFromUsingXXXReasoning(expression, document)

where document is the source of information, and expression is the
thing proved. "says" is a specific form of XXX involving only
subetting the outermost conjunction of a formula (subgraphing
and RDF graph)

</etc/passwd.rdf>  log:says {   :<#timbl> unix:inGroup <#www> } .

means that the file contains at the top level the assertion.
By contrast,

<~/calendar.rdf>   log:impliesByFPC  { :i a cal:OverCommittedPerson } .

means that there is a forst order proof of the conclusion from the evidence
in the document.

Now you can be specific about negation

</etc/passwd.rdf>  log:doesntSay {   :<#timbl> unix:inGroup <#www> } .

we can state a default in a well defined way:

{  </etc/passwd.rdf> log:doesn'tSay { :x unix:inGroup :y } } log:implies
 :x unix:inGroup <#others> } .

tim
Received on Tuesday, 6 March 2001 23:25:36 GMT

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