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

On 13 Oct 2011, at 14:54, Henry S. Thompson wrote:

> 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.

of course a URI considered as a string, as any other string in fact,  appearing in a document - i.e., something that has an interpretation - will be only interpretable as having a specific semantic value given first what the type of that document is chosen to be, and so what its grammar or mode of interpretation is.

For example "http://bblfish.net/#hjs" is a string, which can be parsed as a URI. As such for the moment, when it refers just to the string. But when you then add an interoperation function, for example some toURI function, that takes a string and points to it's referent, then you have

  toUri("http://bblfish.net/#hjs") 

which refers to me. The <a href="..."> is such a context where a string is changed to a URI. Let's write URIs when they are used as such by putting little angle brackets around them like this

   <http://bblfish.net/#hjs>

So that refers to me. And <mailto:henry.story@bblfish.net> refers to my mailbox, by definition of the mailto scheme. Now what is particular about 

    <http://bblfish.net/#hjs>

is that what it refers to is determined not purely analytically by the shape of the URL as with the mailto URL, but is in part defined by what is written in the document <http://bblfish.net/> . The document defines the meaning of that #URL - as per definition of the URL spec.

Then it is very easy to understand [2] below. 

<mailto:henry.story@example.com> refers to my mailbox. But it can indirectly identify me via a inverse functional property.


    <http://bblfish.net/#hjs> foaf:mbox <mailto:henry.story@example.com> .

That is because a function has only 1 value. This is how the number 4 can also be identified by

   2+2
   1+3
   5-1
   1+1+1+1

    etc...

All this seems very easy to me. I even put up a little picture that illustrates this

   http://www.w3.org/wiki/File:X509-Sense-and-Reference.jpg

Henry


> 
> 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.
> 
> ht
> 
> [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]
> 

Social Web Architect
http://bblfish.net/

Received on Thursday, 13 October 2011 13:22:18 UTC