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Re: definition problem?: appending "#foo" without removing "#" from base URI

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Tue, 13 Jan 2004 12:07:04 +0000
To: Daniel Barclay <daniel@fgm.com>
Cc: www-rdf-comments@w3.org
Message-Id: <20040113120704.3cad6b34.dave.beckett@bristol.ac.uk>

On Mon, 12 Jan 2004 16:16:14 -0500 Daniel Barclay <daniel@fgm.com> wrote:

<snip/>

> Could you please clarify:
> 
> * exactly where any restrictions against having a fragment identifier
> are
>    specified (somewhere in RFC 2396, such as its rules on URI
>    resolution? somewhere in the XML Base specification?  somewhere in
>    the RDF/XML specification?), and


in XML Base, which RDF/XML uses, via the XML Infoset:

[[
4.1. Relation to RFC 2396 
RFC 2396 [IETF RFC 2396] provides for base URI information to be embedded
within a document. The rules for determining the base URI can be summarized
as follows (highest priority to lowest):

The base URI is embedded in the document's content.

The base URI is that of the encapsulating entity (message, document, or
none).

The base URI is the URI used to retrieve the entity.

The base URI is defined by the context of the application.

NOTE: The term "entity" in points #2 and #3 above uses the RFC 2396 meaning
of the term. Elsewhere in this document the term "entity" is used in the XML
sense.

This document specifies the details of rule #1 for embedding base URI
information in the specific case of XML documents.
]]
-- http://www.w3.org/TR/xmlbase/#rfc2396

Hence xml:base is used to override any document URI for the resolution of
relative URIs.


However, fragments are not part of a URI.


RFC2396 section 4:

[[
4. URI References

   The term "URI-reference" is used here to denote the common usage of a
   resource identifier.  A URI reference may be absolute or relative,
   and may have additional information attached in the form of a
   fragment identifier.  However, "the URI" that results from such a
   reference includes only the absolute URI after the fragment
   identifier (if any) is removed and after any relative URI is resolved
   to its absolute form.  Although it is possible to limit the
   discussion of URI syntax and semantics to that of the absolute
   result, most usage of URI is within general URI references, and it is
   impossible to obtain the URI from such a reference without also
   parsing the fragment and resolving the relative form.

      URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]
]]
-- http://www.ietf.org/rfc/rfc2396.txt

So URI-reference http://example.org/#fragment is URI 'http://example.org/'
(absoluteURI), plus the fragment identifier 'fragment'


> * where is it specified that any fragment identifier in the base URI
>    must be removed.  (My original concern was that I couldn't find
>    anything in the RDF/XML specification that specified to strip any
>    fragment identifier.)

See the quotes above from XML Base and RFC2396 above.  We
are dealing with URIs for documents and base URIs.

A fragment might be seen in the string content of the attribute
xml:base but it must be removed when the base URI is formed.

  <foo xml:base="http://example.org/#fragment">

the attribute value: http://example.org/#fragment
the base URI: http://example.org/

We check this in the RDF test cases for xml:base I pointed to
previously, plus some other xml:base corner cases.

(There is no XML Base test suite as far as I know)

Dave
Received on Tuesday, 13 January 2004 07:15:34 UTC

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