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Re: Can we express propositonal attitudes twards reified statements in RDF ?

From: Seth Russell <seth@robustai.net>
Date: Thu, 13 Feb 2003 12:58:12 -0800
Message-ID: <3E4C06E4.8050505@robustai.net>
To: www-rdf-comments <www-rdf-comments@w3.org>

pat hayes wrote:

>
>> Pat,
>>
>> The WG agreed:
>>
>>     "The group overwhelmingly, unanimously supports that
>>      we should, in  principle, focus on addressing the
>>      provenance use-case." [1]
>>
>> You said:
>>
>>        "Well, its (literally) impossible to give a coherent 
>> interpretation
>>         of reification which satisfies everyone. We had to choose one,
>>          and we chose the one that seemed to support the existing use
>>          cases that people felt strongly about. "  [2]
>>
>> So can I assume that the subsequent choices of the WG did in fact 
>> support the provenance use-case?
>
>
> Yes.
>
>> Then you say:
>>
>>      "In the present set-up, the reified triple is required to mean
>>        what it would mean if you de-reified it. It refers to the 
>> proposition,
>>        not to the surface syntax. "[3]
>>
>> In the light of the above wouldn't it be more accurate to say that 
>> the reified node refers to the stating of the proposition, and not 
>> the proposition itself ?
>
>
> Yes, it would. There are two dimensions here, in fact, which are kind 
> of orthogonal:
>
> stating/statement  (what the subject of rdf:subject/object et. refer to)
> de re/de dicto (what the object of the reification vocabulary refers to)
>
> We chose the stating/de re combination. What this means, in brief, is 
> this: if I write for example
>
> aaa rdf:subject bbb .
>
> then aaa refers to a stating (not a statement) and bbb does not refer 
> to the syntactic subject of the triple in the stating, which might be 
> a bnode or a uriref (de dicto)., but rather to whatever that subject 
> refers to (de re).  And similarly for rdf:object, etc.
>
> The stating choice was largely motivated by the provenance use case, 
> and that is what your citation [1] refers to. The other choice was 
> also based on consideration of use cases, but I do not recall clearly 
> what they were.
>
> What this combination allows one to do is to state a relationship 
> between a particular document and some entity which the RDF triples in 
> the document are talking about. This was what was needed for the 
> provenance use case, as I recall. 


I don't see that.  "aaa" is the name of the node that would participate
in any stated relationship, not the object of rdf:subject.   What is
more there is no URI of the document which contains the original
statement (if it even exists in a document somewhere) even in the scope
of the reification,  so I fail to see how a reified statement allows us
to "state a relationship between" it or anything else for that matter.
  That last paragraph of yours has totally confused me.

>
>
>> Now we all know that we cannot  substitute in a referentially opaque 
>> context [4]. 
>> I don't follow the reasoning that gets us from there to your statement:
>>
>>    "In a nutshell, :thinks isn't a relationship between
>>      an agent and an RDF reification, so it can't be an RDF property. 
>> "[5]
>>
>> Could you elaborate that reasoning for me?
>
>
> Well, the choice of the de re semantics means that it is possible, in 
> effect, to substitute into a reification context. It isn't technically 
> possible in RDF since there is no RDF equality, but if you put 
> together the intended semantics for RDF reification and those of say 
> OWL, then  the combination
> ...
> aaa rdf:subject bbb .
> bbb owl:sameIndividualAs ccc .
>
> entails
>
> aaa rdf:subject ccc .
>
> So reifications are not opaque; so they are not strictly a suitable 
> choice for representing an opaque context, such as the object of 
> :thinks: or :believes, etc. 

What is the reasoning behind your 'so' .. I still dont get it.

But, bottom line:  it is still my opinion that if the WG knew that the
choice of  de re was going to exclude expressing propositional
attitudes, then they would not have chosen it.  And I fail to see how
not supporting a full complement of propositional attitudes does support
the agreement to address the provenance use-case.   With this de re
option, the way you have defined its semantics, Just what kinds of
useful things are we permitted to say about a reified statement ?

Seth Russell
a dissatisfied customer of RDF.

>>
>> [1] http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Feb/0263.html
>> [2] 
>> http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0237.html
>> [3] 
>> http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0237.html
>> [4] http://gncurtis.home.texas.net/illisubs.html
>> [5] 
>> http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0229.html
>>
Received on Thursday, 13 February 2003 15:59:03 GMT

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