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XML Resource Identifiers

From: Norman Walsh <Norman.Walsh@Sun.COM>
Date: Thu, 16 Feb 2006 10:40:59 -0500
To: public-xml-core-wg@w3.org
Message-ID: <87fymjux9w.fsf@nwalsh.com>
/ Richard Tobin <richard@inf.ed.ac.uk> was heard to say:
| I have a few comments on Francois's XRI definition:

*Please* don't use "XRI" as the acronym for these things. There's an
OASIS TC that's created XRIs (Extensible Resource Identifiers).
They're just reinventing http...nevermind, wrong list. :-)

|     [Definition: *XML resource identifiers* are XML string meant to be used 
|     as IRI references or URI references].  System identifers are XML 
| I think we agreed to change "XML string" to "string" yesterday.  The

To "character string" actually

| definition should probably be changed to be in the singular too: "An
| *XML resource identifier* is a string ...".

I might have done that as well.

|     resource identifiers.  An XML resource identifier may contain characters 
|     that, according to [IETF RFC 3897] and [IETF 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 (most of which cannot 
|     appear in XML)
| Most of these *can* appear in XML 1.1 as character references.
| Character references cannot be used in system identifiers, but you can
| construct an internal entity containing a system identifier containing
| a control character.  I suggest dropping the parenthesized comment.

Works for me.

|          * 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 to them steps 2.1 to 2.3 of 
|     Section 3.1 of [IETF RFC 3987].
|     If necessary for the implementation, an IRI reference is converted to a 
|     URI reference by following the prescriptions of Section 3.1 of [IETF 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.
| What about the XRI->IRI escaping?  Must it happen late?  And I can no
| longer remember exactly what we're getting at here; how exactly can you
| tell whether the conversion was done early or late?
| Also, I would prefer it if the definition actually defined which strings
| are legal XRIs.  It's implicit that they are ones that do in fact result
| in IRIs after the escaping, but this should either be stated explicitly
| or a production should be given.  This seems particularly important for
| Namespaces, where no escaping is in fact done.

Uh....Francois? :-)

                                        Be seeing you,

Norman.Walsh@Sun.COM / XML Standards Architect / Sun Microsystems, Inc.
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Received on Thursday, 16 February 2006 15:41:09 UTC

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