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Links refer, URIs don't (was Re: Fragment Identifiers and Agent Perspectives)

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Thu, 13 Oct 2011 13:54:17 +0100
To: Jonathan Rees <jar@creativecommons.org>
Cc: ashok.malhotra@oracle.com, www-tag@w3.org
Message-ID: <f5bvcrt2gsm.fsf_-_@calexico.inf.ed.ac.uk>
I want to sketch an approaching to rethinking this architectural space
which is similar to but different from Manu's.  For some
background/motivation, interested parties are referred to a recent
talk [1] of the same name.

I think what underlies any number of suggestions about the
introduction/prior existence of some _flexibility_ with respect to
what URIs (with and/or without fragments) identity (e.g. the passages
from 3986 and WebArch which have been quoted, Manu's proposal) is a
more-or-less hidden recognition that the context of use of a URI can,
or even must, be taken into account (alongside the media type of the
document retriev(ed/able) from it, if a fragment is involved) when
determining its referent.

Purely 'linguistic' context of use may be sufficient (what kind of
document does the URI occur in?  What markup, if any, identifies it as
a URI?) in some cases.  In others, not only that, but also the nature
of the agent (client application, human being, server code, . . .)
that is as it were asking the question [tip-of-the-hat to Larry
Masinter] may be needed.

One distinction in terms of context which might prove useful is
between what I'll call 'actionable' and 'referential' contexts.

 <a href="[URI]">...</a> in a document of some ...html... media type, as
 interpreted by a web browser is an actionable context for the
 contained URI.

 <[URI]> rdf:type ... in a turtle or N3 document as interpreted by an
 RDF processor is a referential context for the contained URI.

Four examples, increasingly contentious:

 1) mailto:nadia@example.com -- in an actionable context this
    identifies a mailbox, in a referential context it identifies a
    person.  The context distinction is the only way I can make sense
    of the discussion at [2].

 2) http://www.example.org/PurchaseOrder.xsd#Items -- in an actionable
    context, e.g. <xi:include href="..."/> in another XML schema
    document being processed by an XInclude-supporting processor, it
    identifies an XML element, whereas in a referential context, it
    identifies the Complex Type Definition component named 'Items' in
    the schema corresponding to the named schema document.

 3) http://example.org/people.html#noah -- in an actionable context
    this identifies an element in an (X)HTML document, in a
    referential context (presuming there's some appropriate RDFa in
    the relevant document) it identifies a person.

 4) http://dbpedia.org/resource/Albert_Einstein -- in an actionable
    context, this identifies an RDF graph, in a referential context it
    identifies a person.


[1] http://www.ltg.ed.ac.uk/~ht/PhilWebURIs.pdf
[2] http://www.w3.org/TR/webarch/#indirect-identification
       Henry S. Thompson, School of Informatics, University of Edinburgh
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 651-1426, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
 [mail from me _always_ has a .sig like this -- mail without it is forged spam]
Received on Thursday, 13 October 2011 12:54:49 UTC

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