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Re: entailment-from-inconsistent-graph [was: proposed test of RDFS entailment rules]

From: Jos De_Roo <jos.deroo@agfa.com>
Date: Sat, 18 Oct 2003 20:25:11 +0200
To: "pat hayes <phayes" <phayes@ihmc.us>
Cc: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, "w3c-rdfcore-wg" <w3c-rdfcore-wg@w3.org>
Message-ID: <OFD7DE6283.B7A7DAC2-ONC1256DC3.0063DBA5-C1256DC3.006531D4@agfa.be>

[is redirected from rdf-comments to rdf-core]

Pat - that * suggestion is actually a very good one.
I've done a small test (just this particular case but
it could be generalized to all XML clashes and
maybe also other datatype clashes, but then we
need a bit more time to write code to invoke
XML parsers and/or datatype checkers).
The results are reflected in following proof

@prefix iw: <http://www.ksl.stanford.edu/software/IW/spec/iw#>.
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
@prefix eg: <http://example.org/eg#>.
   {[iw:Variable "?A"] = rdf:XMLLiteral.
    [iw:Variable "?B"] = rdfs:Literal.
    [iw:Variable "?A"] rdfs:subClassOf [iw:Variable "?B"]} =>
  {rdf:XMLLiteral rdfs:subClassOf rdfs:Literal}.
     {[iw:Variable "?P"] = eg:prop.
      [iw:Variable "?C"] = rdf:XMLLiteral.
      [iw:Variable "?P"] rdfs:range [iw:Variable "?C"]} =>
    {eg:prop rdfs:range rdf:XMLLiteral}.
     {[iw:Variable "?S"] = eg:foo.
      [iw:Variable "?P"] = eg:prop.
      [iw:Variable "?O*"] = "<"^^rdf:XMLLiteral.
      [iw:Variable "?S"] [iw:Variable "?P"] [iw:Variable "?O*"]} =>
    {eg:foo eg:prop "<"^^rdf:XMLLiteral}.
    [iw:Variable "?S*"] = "<"^^rdf:XMLLiteral.
    [iw:Variable "?A"] = rdf:XMLLiteral.
    [iw:Variable "?S*"] a [iw:Variable "?A"]} =>
  {"<"^^rdf:XMLLiteral a rdf:XMLLiteral}.
  [iw:Variable "_:Y_3*"] = "<"^^rdf:XMLLiteral.
  [iw:Variable "_:Y_3*"] a rdfs:Literal} =>
{"<"^^rdf:XMLLiteral a rdfs:Literal}.

in which you should see 6 occurences of *'ed variables
and an appropriate proof checker is informed that way.

Till now, I made separate rules to derive inconsistencies
but maybe this way is better; any further thoughts??

Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/

                      pat hayes                                                                                                           
                      <phayes@ihmc.us>            To:       Jos De_Roo/AMDUS/MOR/Agfa-NV/BE/BAYER@AGFA                                    
                      Sent by:                    cc:       "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>,                     
                      www-rdf-comments-req         www-rdf-comments@w3.org, www-rdf-comments-request@w3.org                               
                      uest@w3.org                 Subject:  Re: entailment-from-inconsistent-graph [was: proposed test of  RDFS           
                                                   entailment  rules]                                                                     
                      2003-10-18 03:18 PM                                                                                                 

The current (editor's draft) RDFS rules have a
criterion for detecting inconsistency, to wit,
the derivation of a triple called an 'XML clash'.

_:nnn rdf:type rdfs:Literal .

where the subject bnode _:nnn was introduced, and
allocated to an ill-typed literal by, the lg
generalization rule (formerly called rdf2). The
derivation for this example is as follows:



<http://example.org/prop> _:1*.      rule lg,
with _:1* allocated to
which is ill-typed. (Jos, can your code keep
track of this when the rule is applied and 'mark'
the bnode accordingly?)

<http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral> .   rule rdfs3

<http://www.w3.org/2000/01/rdf-schema#Literal> .
RDFS axiomatic triple

_:1* <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://www.w3.org/2000/01/rdf-schema#Literal>  .               rule rdfs9

So the 'ex cont quod' could reasonably be
restricted to this case, ie if you really believe
an XML clash then you will believe anything.
However, notice that the clash itself is not
inconsistent: it is a symptom of the original set
being inconsistent. So it would not be correct to
say that the silly conclusion is entailed by the
clash; rather, if you can derive a clash from a
graph, then  the silly conclusion is entailed by
your original graph.

>What a coincidence - while sitting in a plane this evening
>I did't think to implement a "ex contradictione quodlibet".
>The premise graphs are assumed to be the case unless they
>can be proven to be inconsistent and then we just say so
>and don't explicitly use them further. So we can't
>run that testcase.

I think it would be OK to be able to prove the
antecedent inconsistent, and call that a proper
run of the test-case. I think that was Peter's
main point.


>Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/

>                       Brian

>                       <bwm@hplb.hpl.hp.com
>To:       "Peter F. Patel-Schneider"
>                       >

>                       Sent by:
>Subject:  entailment-from-inconsistent-graph
>[was: proposed test of RDFS entailment
>                       www-rdf-comments-req




>                       2003-10-15 03:37



>The WG were unable to discuss this suggestion before publishing the 2nd
>last call documents.  I propose to track this as a 2nd last call comment:

>Peter F. Patel-Schneider wrote:
>>  I propose that the following be a positive entailment test in the RDF
>>  suite.  This is a valid RDFS entailment (modulo typing errors), but is
>>  a consequence of the current RDFS entailment rules.
>>  Premise
>  > <http://example.org/prop> <http://www.w3.org/2000/01/rdf-schema#range>
>http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral> .
>>  <http://example.org/foo> <http://example.org/prop> "<"^^<
>http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral> .
>  >
>>  Conclusion
>>  <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
>http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
>http://www.w3.org/1999/02/22-rdf-syntax-ns#type> .
>>  Peter F. Patel-Schneider

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Received on Saturday, 18 October 2003 14:27:16 EDT

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