Re: #rdfms-identity-anon-resources: provenance

>At 10:27 PM 7/23/01 -0700, pat hayes wrote:
>>>I was chatting with a colleague to day and the subject of anon resources
>>>and provenance came up.
>>>
>>>Assume I recieve the following rdf from some source SOURCE, possibly with a
>>>digital signature:
>>>
>>><rdf:Description>
>>>  <foo:bar>foobar</foo:bar>
>>></rdf:Description>
>>><rdf:Description rdf:about="http://goo">
>>>  <foo:bar><foobar</foo:bar>
>>></rdf:Description>
>>>
>>>If were to represent this in my machine as:
>>>
>>><gensym:1234> <foo:bar> "foobar" .
>>><http://goo>  <foo:bar> "foobar" .
>>>
>>>this is not the information that SOURCE signed - SOURCE made no assertion
>>>about <gensym:1234>.  We'd have to be able to distinguish between the
>>>gensym'd URI and the 'real' one.
>>
>>As I said a while ago, it matters who generates the gensym. If 
>>SOURCE uses an anonymous node (existential quantifier) then indeed 
>>you are not entitled to replace it with a gensym and say that it 
>>represents what SOURCE said.
>
><aside>
>Is this in any sense related to Pierce's concepts of "Firsness", 
>"Secondness" and "Thirdness" (using terms from John Sowa's book on 
>Knowledge Representation, section 2.2, p60)?

Aaargh. I really don't know. This is one (of the very few) aspects of 
Sowa's thinking that seems to be completely off the wall. I have had 
many debates with him about it, some lasting for years. Other 
Peircian scholars seem to have the same obsession with this stuff, 
sometimes amounting almost to a religious conviction in a kind of 
Peircian revealed truth. Nobody else seems to think it anything more 
than an embarrassment or a joke, a kind of numerology. I have come to 
the conclusion that there isn't anything in this 
'firstness/secondness/thirdness' that is worth talking about at any 
length, so I won't.

>Taken in isolation, the statements of RDF seem to express ideas at 
>the level of "Secondness" -- relationship between things (and 
>"Firstness" -- types; characteristics inherent in things).
>
>It seems that a bare statement of a relationship (Secondness) may 
>not be affected by use of an existential or a Skolem, but that you 
>are suggesting here that a statement of mediation (Thirdness) may be 
>sensitive to the difference.

Well, if I was saying that, I wasn't aware of it :-)

>
>(I am beginning to wonder if the concept of provenance, or assurance 
>is a "Thirdness" beyond the ability of basic RDF to capture.  In my 
>attempts to capture such things in RDF, I've invoked ideas like 
>contexts which, in turn, seem to require that statements are 
>mappable to quadruple elements, or triadic predicates.  I'm still 
>absorbing some of this stuff, so can't fully separate fundamentals 
>from coincidental artefacts.)
></aside>
>
>>That is what the logic says also: the step from the existential to 
>>the skolem form is *not* a valid inference, so you would not be 
>>correct in saying that conclusion followed from what SOURCE said. 
>>However, SOURCE could have replaced his existential with a skolem 
>>constant ( a newly generated URI, guaranteed different from any 
>>other URI anywhere else) and, my claim is, that you would have been 
>>told virtually the same content by SOURCE under those circumstances 
>>as you would have been by SOURCE telling you his existential. (Not 
>>quite *exactly* the same, since you would know, in addition to the 
>>fact that the thing exists, that SOURCE was using this URI to refer 
>>to it. But that information wouldnt help you make any inferences 
>>about the thing that you couldnt have made from the existential.) 
>>But indeed, if someone signs a document then it isnt, in general, 
>>correct to transfer that signature to another document that differs 
>>even in the slightest respect, so the issue of whether the 
>>inferences are valid or not may be irrelevant here.
>
>In this case, a possible difference that I perceive is that:
>(a) when given the existential in a statement, the receiver knows 
>that no more information specifically about that resource can be 
>received

I guess so, though you would only know that if you knew that you had 
received the whole document since that is where the existentials are 
quantified (see discussion in the strawdog model theory).

>(unless that already provided constitutes a definite description),

Right, but it can't in RDF since the definite description uses a 
universal quantifer.

>(b) when given a constant identifier (which may or may not be a 
>skolem, and the receiver cannot know), then there is a possibility 
>that more information about the resource may be received in the 
>future.

Right.

>Then my question would be:  is this a difference we need to capture?

Good question.

Pat

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Received on Thursday, 26 July 2001 18:14:37 UTC