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Re: XLink 1.1: xlink:href requirements

From: Bjoern Hoehrmann <derhoermi@gmx.net>
Date: Wed, 25 Jan 2006 16:45:58 +0100
To: Norman Walsh <Norman.Walsh@Sun.COM>
Cc: www-xml-linking-comments@w3.org
Message-ID: <626ft19k6rjvk3ruoafjp0ghe1uo4q3kg6@hive.bjoern.hoehrmann.de>

* Norman Walsh wrote:
>Because it is impractical for any application to check that a value is
>a URI reference, this specification follows the lead of [RFC 3986] in
>this matter and imposes no such conformance testing requirement on
>XLink applications.

I note that the XML Core Working Group told me back in December this
text will not appear in XLink 1.1 as above, so it's quite odd to see
it here several weeks later.

>If the value of the href attribute is a relative URI, or results in a
>relative URI after escaping, its absolute version must be computed by
>the method of [XML Base] before use.


>5.4.1 XML Resource Identifiers

I gather the XML Core Working Group plans to introduce this new term
across a broad set of specification, possibly making changes that affect
conformance. For example, the current XLink 1.1 draft does not allow use
of C0 control characters in the xlink:href attribute value as far as I
can tell.

>An [Definition: XML resource identifier is an XML string meant to be

The term "XML string" seems undefined.

>used as an IRI reference or URI reference.] An XML resource identifier
>may contain characters that, according to [RFC 3987] and [RFC 3986],
>must be escaped before the string can be used to retrieve the
>referenced resource. To convert an XML resource identifier to an IRI
>reference, the following characters must be escaped:
>    * the control characters #x0 to #x1F and #x7F
>    * space #x20
>      Note:
>      Authors are advised to avoid unescaped spaces, as XML Schema has
>      identified them as an interoperability risk.
>    * the delimiters "<" #x3C, ">" #x3E and """ #x22
>    * the unwise characters "{" #x7B, "}" #x7D, "|" #x7C, "\" 
>      #x5C, "^" #x5E and "`" #x60
>These characters are escaped by applying steps 2.1 to 2.3 of Section
>3.1 of [RFC 3987] to them.
>If required, an IRI reference can be converted to a URI reference by
>following the prescriptions of Section 3.1 of [RFC 3987]. This
>conversion must be performed only when absolutely necessary and as
>late as possible in a processing chain. In particular, neither the
>process of converting a relative IRI to an absolute one nor the
>process of passing a IRI reference to a process or software component
>responsible for dereferencing it should trigger escaping.

Did the TAG, XCG, HCG, and I18N Core WGs review this definition? Why is
this put in the XLink 1.1 draft rather than a more appropriate place? I
don't think it's a good idea to encourage silent error recovery here,
nor does it seem to be a good idea to allow the space for these general
purpose "XML resource identifiers" since that precludes use e.g. of
"space-separated lists of XML resources identifiers".
Björn Höhrmann · mailto:bjoern@hoehrmann.de · http://bjoern.hoehrmann.de
Weinh. Str. 22 · Telefon: +49(0)621/4309674 · http://www.bjoernsworld.de
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Received on Wednesday, 25 January 2006 15:45:17 UTC

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