W3C home > Mailing lists > Public > www-rdf-interest@w3.org > February 2003

Re: Statings -- Much ado about nothing

From: Bob MacGregor <macgregor@ISI.EDU>
Date: Fri, 07 Feb 2003 15:04:17 -0800
Message-Id: <5.1.1.6.0.20030207145740.00bc4310@tnt.isi.edu>
To: Seth Russell <seth@robustai.net>
Cc: www-rdf-interest@w3.org

Hi Seth,

At 01:25 PM 2/7/2003 -0800, Seth Russell wrote:
>Bob MacGregor wrote:
>
>> >> The RDF reification vocabulary consists of a class name and three 
>> property
>> >> names.  Semantic extensions MAY limit the interpretation of these so that
>> >> a triple of the form
>> >>      aaa rdf:type rdf:Statement .
>> >> is true in I just when I(aaa) is a token of an RDF triple in some RD
>> >> document, and the three properties, when applied to such a denoted 
>> triple,
>> >> have the same values as the respective components of that triple.
>>
>>However, the caveats are legion:
>>
>>First, its says that 'extensions' may limit the interpretation.  This means
>>that RDF itself places no such limitations.
>>
>>Second, it refers to a triple in 'some' RDF document.  Nothing relates the
>>document where a stating occurs to that other document.  From an 
>>implementation
>>perspective, this means that there is no possible way that one could verify
>>that the triple referred to does not in fact exist, i.e., it is
>>impossible to check whether or not the triple that a stating refers to
>>does or does not exist.
>
>Sure there is a way:  the document (source, or database) which contins the 
>original triple is just more metadata about the stating.  If an 
>application needs that information, then it should annotate the stating 
>accordingly ... perhaps like the following:
>
>  _:1  rdf:type rdf:Statement
>  _:1  rdf:subject <Xsubject>
>  _:1 rdf:predicate <Ppredicate>
>  _:1 rdf:object <Oobject>
>  _:1 ex:containedIn <http:foo/bar.rdf>
>  _:1 ex:sethComment "The fact that, that statement is in that document, 
> sucks big time"

My point is completely different.  I'm not claiming that you can't invent a
way to find the matching/original triple.  I'm claiming that, because there is
no *official* way to find it, and more importantly, because there is no 
requirement
that such information need exist, there is no way for an automated verifier
to tell whether or not the triple exists.  Hence, no way, using the official
RDF vocabulary and semantics, to verify whether or not the stating is "valid".
Therefore, all statings are valid (unless one counts ones that point to 
literals
in the Xsubject, Ppredicate, or Oobject positions).

Cheers, Bob





>Seth Russell
>http://radio.weblogs.com/0113759/
>

Robert MacGregor
Project Leader
USC Information Sciences Institute
4676 Admiralty Way, Marina del Rey, CA 90292
macgregor@isi.edu
Phone: 310/448-8423, Fax: 310/822-6592
Mobile: 310/251-8488
Received on Friday, 7 February 2003 18:04:33 GMT

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