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Re: web proper names

From: Henry Story <henry.story@bblfish.net>
Date: Mon, 20 Sep 2004 21:39:04 +0200
Message-Id: <BAAAFEFE-0B3C-11D9-AB5A-000A95D9FA7A@bblfish.net>
Cc: Jon Hanna <jon@hackcraft.net>
To: <www-rdf-interest@w3.org> <www-rdf-interest@w3.org> <www-rdf-interest@w3.org> <www-rdf-interest@w3.org>

On 20 Sep 2004, at 18:39, Jon Hanna wrote:

>> In particular the use/mention distinction has really helped locate a
>> problem that has kept bugging me when thinking about rdf.
> The analogy is false IMO. Mentioning a URI is saying something like 
> "The
> URI 'http://www.example.net/blah' has 27 characters, uses the common
> convention of naming a webserver 'www', has no query-string and doesn't
> use any of character escapes defined in RFC 2396".

I have to agree. I had half thought about this, when reading it, but 
was then take by the following example.

> On the other hand both using a URI to identify a resource and to
> retrieve a representation are using URIs.
>> This can be summarized by considering the following triples which
>> though formally contradictory, can in fact be seen to be compatible:
>> (A)     http://www.paris.org/Monuments/Eiffel
>>              http://purl.org/dc/elements/1.1/creator
>>          http://www.gustaveeiffel.com/
>> (B)     http://www.paris.org/Monuments/Eiffel
>>              http://purl.org/dc/elements/1.1/creator
>>          http://www.endex.com/gf/
>> If we only understand the above names to be used then the two
>> sentences
>> are contradictory.
>> (A) states that the Eiffel Tower was created by Gustav
>> Eiffel, whereas
>> (B) states that
>> it was created by Gary Feuerstein. (A) is true in this
>> interpretation,
>> whereas (B) is false.

I like your short explanation of this on the www-tag mailing list [1]

>> Harry's solution is to assume that rdf resources by default point to
>> the representation of the resource and not the thing itself, and then
> You can't even assume that a resource has a representation, or that
> there is only one. Assuming that this is what is being referred to is
> hence falls long before the first fence.
> (Also, I dispute the use of the term "rdf resources". There are
> resources. RDF is a way to describe them.)
>> to add a new wpn:// scheme to help create names that refer
>> directly to
>> an object.
> It follows from the argument that URIs don't identify resources that we
> need some sort of uniform resource identifier. I don't buy the problem,
> so I don't buy the solution.
>  It occurs to me right now that from a philosophical
>> perspective this cannot quite be the correct solution, since the
>> arguments have always been that names can be used in both ways.

I was thinking of the use/mention distinction. Whatever name you find 
you will
always be able to use it and mention it, so creating a new naming 
scheme is not
going to help.

> I've hardly ever heard this argued. What I have heard argued is:
> 1. URIs identify any sort of thing. When used with a given system (the
> web) they result in representations being returned. When used otherwise
> the system in question does whatever is appropriate for it to do with
> respect to that thing.
> 2. URIs identify "conceptual documents". When used with the web they
> result in a particular document being returned, which in regards to 
> such
> matters as content-type, language and other negotiable features is an
> instance of the more Platonic "conceptual document" (which is not in a
> particular language or content-type).
> Just because you get a representation when you do a particular action
> with it no more makes that representation the thing the URI identify
> than using my name in an enquiry makes "Jon Hanna" intrinsically bound
> to "Quite tall, shaven head, wears black a lot". It certainly doesn't
> make it bound to that and nothing else.

I agree.

>> Would it perhaps not be easier to extend RDF so that one can
>> point to a
>> resource in either way, for example by allowing the following:
>> <Entry rdf:about="http://www.paris.org/Monuments/Eiffel">
>> or
>> <Entry rdf:refers="http://www.paris.org/Monuments/Eiffel">
> That isn't extending RDF, it's extending RDF/XML. I think the way to
> extend RDF to deal with this is to define a predicate that defines the
> relationship between the resource identified by the URI and the zero or
> more representations that may be returned when you dereference it's
> URIs.

This type of relation is what I would like to better understand.

> (Amusingly one could usefully mention URIs for real here since a
> resource can have more than one URI, but the representation returned 
> may
> depend on which one is used - this is a feature of the character 
> strings
> the webserver received, not of the URI qua resource identifier.)
>> I have been confused a few times about this exact problem,
>> and am very
>> thankful to Harry Halpin, and Henry S.Thompson for the clear
>> explanation of this problem.
> I think the waters are muddier now.

For me they are a little clearer, but I think that is because I was in 
the dark.
I just happened upon this debate, and am looking forward to getting a 
better grasp on the concepts involved.

Henry Story

[1] http://lists.w3.org/Archives/Public/www-tag/2004Sep/0115.html
Received on Monday, 20 September 2004 19:39:24 UTC

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