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Re: ISSUE-58: Scalability of URI Access to Resources

From: Xiaoshu Wang <wangxiao@musc.edu>
Date: Fri, 07 Sep 2007 13:36:35 +0100
Message-ID: <46E145D3.4010607@musc.edu>
To: "Williams, Stuart (HP Labs, Bristol)" <skw@hp.com>
CC: Chimezie Ogbuji <chimezie@gmail.com>, www-tag@w3.org

I think, what is at debate or unclear is this.  Given a sentence, such as

_:me a foaf:Person.

What is the meaning of it?  Is the meaning expressed by just that 
sentence alone or is it by that statement plus the FOAF ontology (due to 
follow the link)?  I think OWL and RDF uses two different models.  OWL 
uses explicit import, but RDF use follow-your-nose approach because 
there isn't any "import/include". 

The "RDF URI" that Chimezie coined may mean the the latter usage while 
the "symbol" is the URI used in OWL. The confusion is: given or writing 
an RDF document, how do I know if I should follow the nose or not 
because the interpretation and complexity can be quite different for two 
respective treatment.

Xiaoshu


Williams, Stuart (HP Labs, Bristol) wrote:
> Hello Chimezie,
>
> So... I'm going to be a little obtuse, maybe deliberately so... but
> maybe I should also make it clear what is bugging me, which is the use
> of the prefix RDF in the term "RDF URI"... they are just URIs... I don't
> see what insisting on calling them "RDF URI" buy's you.
>
>   
>> On 8/28/07, Williams, Stuart (HP Labs, Bristol) <skw@hp.com> wrote:
>>     
>>> Hello Chimezie,
>>>
>>> Probably  couple of obtuse questions...
>>>
>>> - How do "RDF URI" differ from URI in general?
>>>       
>> I tried to cover some of this in the following Wiki:
>>     
> http://esw.w3.org/topic/RDFSemiotics
>
> I'm afraid that didn't help me :-(. I certainly understood the semiotic
> triangle stuff and have been exposed to it before.
>
> As 'symbol' what makes "RDF URI" (your term)  different from URI in
> general.
>
>   
>> This is mostly a rehash from http://www.w3.org/TR/rdf-mt/ (so 
>> I hope Pat will slap me on the hand when I'm chatting 
>> rubbish), but generally, RDF URIs are 'symbols' which denote 
>> things in an interpretation (a 'theory').
>>     
>
> And URI in general do not? Even in the particular interpretation that we
> might commonly call 'the web'?
>
>   
>> The expressions in 
>> which the RDF URIs are used describe a set of conditions that 
>> must be met to satisfy the interpretation.  The end-game 
>> (goal, if you wish) is "to provide a technical way to 
>> determine when inference processes are valid, i.e.
>> when they preserve truth."
>>     
>
> I don't understand how I can tell whether or not I'm using an "RDF URI".
> OTOH, I can tell when I'm using a URI in RDF (or HTML or an email or...)
>
>   
>> The main difference is that the domain of discourse is a 
>> superset of what Web architecture is primarily concerned 
>> with: information resources and their representations.  
>>     
>
> Though I think Pat would wish it otherwise, I don't think that in terms
> of the denotation of URIs, the domain of discourse in Web Arch is
> constrained in the way that you describe.
>
>   
>> Whereas in a model-theoretic language, the 'semantics' are 
>> determined from the expressions which make use of the RDF 
>> URIs, Web architecture is (or it seems that way from the 
>> specific best practices in AWWW) primary concerned with the 
>> consumption of information resources to meet a different 
>> goal: a user browsing a page, or a web crawler browsing pages 
>> to create indices for subsequent searching.
>>     
>
> Hmmm.... I'll think about that. There is a particular artiefact, AWWW, a
> document which is an expression of a set of principles and best
> practices that we could agree on (at the time). However, there is the
> much larger conceptual artifact of "The Architecture of the Web". Whilst
> AWWW speaks mostly of what it calls "information resources" the scope of
> what URIs can (and I'll use the word here risking a blast from Pat)
> identify (by which I mean 'refer-to') is unconstrained by AWWW.
>
>   
>> In addition, outside of the consumption of information 
>> resources, there is no 'formal' mechanism to follow to 
>> 'interpret' or infer 'meaning' from web resources (other than 
>> specific representation formats - which are primarily 
>> concerned with syntax not 'semantics' )
>>
>>     
>>> - How would a recognise that a given URI is an "RDF URI"?
>>>       
>> By the context of its use.
>> http://metacognition.info/profile/webwho.xrdf#chime is the 
>> URI I've 'minted' to represent me.  
>>     
>
> ok...
>
>   
>> When used as a link in an 
>> HTML document, it is simply a (typed) link to my FOAF 
>> document.
>>     
>
> Hmmm... less ok... assuming that you are serving as
> "application/rdf+xml" the by virtue of the RDF media type definition
> that is still a reference to you, the person, rather than a bit of text
> in an RDF/XML representation of a graph - or more accurately it is a
> reference to a/the thing in an intepretation which statisfies the
> assertions made in the graph (which in all probability is you).
>
> ie. that that reference is made in an HTML document has not changed the
> intended referent of the URI.
>
>   
>>  When parsed by an RDF 'agent' - from that FOAF 
>> (RDF) document - it is understood to 'denote'
>> Chimezie Ogbuji (me).  
>>     
>
> And somehow the intended referrent is/or may be different if parsed from
> an HTML representation? IMO that is *not* an intention of Web
> Architecture.
>
> FWIW: I believe that "unique denotation of URI" is an intention the
> design of Web Architecture; I am equally aware that such a position
> denies "context of use" as a means to disambiguate the referrents of
> referring expressions. I am equally aware that in general the context in
> which a referring expression occurs can be significant. I have never
> been able to square that circle - though the closest I have come is to
> regard the web as one big context and referrents of references made
> using URI as invariant within that (large) context. It seems like a
> design choice in the design of Web Architecture - it is I think the
> place where the constraints of the Web apply to the semantic web. 
>
>   
>> So, the expressions which make use of 
>> this URI are the constraints which apply in order to meet the 
>> interpretation expressed in that FOAF graph.
>>
>>     
>>> Thanks,
>>>
>>> Stuart Williams
>>> --
>>> Hewlett-Packard Limited registered Office: Cain Road, 
>>> Bracknell, Berks
>>> RG12 1HN
>>> Registered No: 690597 England
>>>       
>
> Thanks,
>
> Stuart
> <snip/>
>   
>
>
>   
Received on Friday, 7 September 2007 12:37:08 UTC

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