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Re: Statings -- Much ado about nothing

From: Seth Russell <seth@robustai.net>
Date: Fri, 07 Feb 2003 15:45:20 -0800
Message-ID: <3E444510.9080900@robustai.net>
To: Bob MacGregor <macgregor@ISI.EDU>
CC: www-rdf-interest@w3.org

Bob MacGregor wrote:

> 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). 

Yes, the stating *is* valid, independant of whether the triple it 
describes was asserted in any prticulr document or not.   Consider the 
case of a supposition:  "Were you to state that  'Sadam has no wepons of 
mass destruction', you would be in error."  Well you never did state 
that,  but we can still talk about such a stating anyway.   Also there 
is no such concept as the "official" triple.  There may be none (or 
many) triples scattered anywhere on the semantic web that qualify 
according to the criteria in the reified node  -  just which ones of 
those that are being described needs to be restrained by further 
metadata in the stating node.  True, RDF vocabulary gives us no standard 
way to encode that metadata; but then I dont think they could have 
defined that vocabulary without defining "context"; and ... alass....  
that's something they couldn't bring themselves to do.     

Needlessly to say,  this is only my opinion.

Seth Russell
Received on Friday, 7 February 2003 18:45:52 GMT

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