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Re: [OWLWG-COMMENT] ISSUE-67 (reification): real semantic-free RDF-comments

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Thu, 29 Nov 2007 14:42:00 +0000
Message-ID: <474ECFB8.2030705@hpl.hp.com>
To: Alan Ruttenberg <alanruttenberg@gmail.com>
CC: Pat Hayes <phayes@ihmc.us>, Michael Schneider <schneid@fzi.de>, Owl Dev <public-owl-dev@w3.org>, Ian Horrocks <horrocks@cs.man.ac.uk>, bmotik@cs.man.ac.uk


Rather than talk about universal role, i.e. an object property; I 
perhaps should have talk about a universal attribute, i.e. a data 
property; or even the union of the two). In RDF, since all literals are 
resources, a universal role is a universal attribute.


A worked example is given in:

http://www.hpl.hp.com/techreports/2003/HPL-2003-142.html

Briefly, to make RDF canonicalization work effectively, I needed a 
source of meaningless triples, that I could add or delete freely without 
changing the semantics of the graph. For simplicity I sufficed with a 
near-universal attribute, with range xsd:long.

This can be achieved by defining the appropriate semantics of a new 
property as a semantic extension to RDF, or, less formally, with:


<rdf:RDF xml:base=”&c14n;” xmlns:c14n=”&c14n;#”>
   <rdfs:Property rdf:ID=”true”>
     <rdfs:description>This property is true whatever
resource is its subject, and whatever literal is its object.
Thus triples with literal objects, and c14n:true as
predicate, can arbitrarily be added to and deleted from an RDF
graph without changing its meaning. </rdfs:description>
   </rdfs:Property>
<rdf:RDF>

Or within OWL 1.0, with the defn

class(rdfs:Resource complete
       restriction(c14n:true cardinality=2^64))
       dataValuedProperty( c14n:true range( xsd:long ) )


In OWL 1.1, we have already had the universal role defined by:
http://lists.w3.org/Archives/Public/public-owl-dev/2007OctDec/0074
(modified)

 >   (A0) ClassAssertion(w owl:Thing)
 >   (A1) SubClassOf(owl:Thing ObjectHasValue(pA w))
 >   (A3) SubObjectPropertyOf(
 >          SubObjectPropertyChain(pA InverseObjectProperty(pA))
 >          pU )
 >   (A4) ObjectPropertyDomain(pU owl:Thing)
 >   (A5) ObjectPropertyRange(pU owl:Thing)

A4 and A5 seem unnecessary

The universal attribute cannot be defined directly in OWL 1.1 DL, 
mapping this construct to use DataProperty's hits various limits.

The universal attribute can simply be defined by fiat as the product of 
owl:Thing by rdfs:Literal (mapped into the appropriate domain of 
interpretation). Then it would be possible to have every annotation 
property defined as having such an extension. Then they would be 
explicitly meaningless, in that knowing that such an annotation held 
would tell you nothing.

But consider an axiom that is legally actionable: e.g. an axiom that 
contains within one or more of:

a) a libellous statement (e.g. classifying somebody within an offensive 
class)

b) a culpably negligent proposition e.g.
    subClassOf( owl:Thing, eg:KnownToBeSafeToConsume )

   (which could well result in poisoning)

Suppose that annotations are semantic free, then for either of these 
axioms, attribution information, such as who wrote them, can be freely 
added or deleted, and the culpability involved, would be ascribed 
mistakenly.

Annotations have semantics. The question is what semantics.

Jeremy
Received on Thursday, 29 November 2007 14:42:36 GMT

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