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Re: #rdfms-difference-between-ID-and-about

From: Graham Klyne <Graham.Klyne@Baltimore.com>
Date: Fri, 15 Jun 2001 14:50:44 +0100
Message-Id: <5.0.2.1.2.20010615144632.03713880@joy.songbird.com>
To: Dan Brickley <danbri@w3.org>
Cc: rdf core <w3c-rdfcore-wg@w3.org>
I note that one of the options for 5.1.2 is "None".  The transfer protocol 
*might* supply a value, but then again it might not.

Maybe we might say that a relative URI is meaningful only if there *is* a 
URI (per 5.1.1-5.1.4) relative to which it can be evaluated?

#g

At 07:45 AM 6/15/01 -0400, Dan Brickley wrote:
>On Fri, 15 Jun 2001, Graham Klyne wrote:
>
> > At 02:29 AM 6/15/01 -0500, Dan Connolly wrote:
> > > > RDF absolutely has to make sense even outside the context of
> > > > an enclosing document which can be given a uri. so ...
> > >
> > >So... what? That doesn't make any sense to me.
> > >
> > >An RDF document is an XML document. Each XML document
> > >has a base URI (cf the infoset spec).
> >
> > If this is  true, then it is not possible to transfer RDF data in transient
> > protocol elements.
> >
> > Which means that (say) the CC/PP spec, formulated *by design* as a *format*
> > only for client capability data, cannot be regarded as a valid RDF 
> application.
>
>Can't we just say that it picks up the base URI from (broadly conceived)
>surrounding context? It remains true that each XML document has a base
>URI. How we determine that base is the only issue here.
>
>
>RFC2396 is pretty clear on this. See:
>http://www.faqs.org/rfcs/rfc2396.html section 5.1: establishing a base URI
>
>Both XML Protocol and CC/PP use seems to fall under 5.1.2, 'base URI of
>the encapsulating entity'. XML:base, by contrast, looks to fall under
>'base URI embedded in document's content'.
>
>[[
>5.1. Establishing a Base URI
>    The term "relative URI" implies that there exists some absolute "base
>    URI" against which the relative reference is applied.  Indeed, the
>    base URI is necessary to define the semantics of any relative URI
>    reference; without it, a relative reference is meaningless.  In order
>    for relative URI to be usable within a document, the base URI of that
>    document must be known to the parser.
>    The base URI of a document can be established in one of four ways,
>    listed below in order of precedence.  The order of precedence can be
>    thought of in terms of layers, where the innermost defined base URI
>    has the highest precedence.  This can be visualized graphically as:
>       .----------------------------------------------------------.
>       |  .----------------------------------------------------.  |
>       |  |  .----------------------------------------------.  |  |
>       |  |  |  .----------------------------------------.  |  |  |
>       |  |  |  |  .----------------------------------.  |  |  |  |
>       |  |  |  |  |       <relative_reference>       |  |  |  |  |
>       |  |  |  |  `----------------------------------'  |  |  |  |
>       |  |  |  | (5.1.1) Base URI embedded in the       |  |  |  |
>       |  |  |  |         document's content             |  |  |  |
>       |  |  |  `----------------------------------------'  |  |  |
>       |  |  | (5.1.2) Base URI of the encapsulating entity |  |  |
>       |  |  |         (message, document, or none).        |  |  |
>       |  |  `----------------------------------------------'  |  |
>       |  | (5.1.3) URI used to retrieve the entity            |  |
>       |  `----------------------------------------------------'  |
>       | (5.1.4) Default Base URI is application-dependent        |
>       `----------------------------------------------------------'
>[...]
>
>]]
>
>Dan

------------------------------------------------------------
Graham Klyne                    Baltimore Technologies
Strategic Research              Content Security Group
<Graham.Klyne@Baltimore.com>    <http://www.mimesweeper.com>
                                 <http://www.baltimore.com>
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Received on Friday, 15 June 2001 09:58:31 EDT

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