[xX][mM][lL] is reserved

James Clark jjc at jclark.com
Fri May 8 10:52:08 BST 1998

Chris Lovett wrote:
> Spec issue:
> Section 2.3 paragraph 3:
>         "A Name is a token beginning with a letter or one of a few
> punctuation characters, and continuing with letters, digits, hyphens,
> underscores, colons, or full stops, together known as name characters.
> Names beginning with the string "xml", or any string which wouild match
> (('x' | 'X')('m' | 'M') ('l' | 'L')) are reserved for standardization in
> this or future versions of this specification".
> Currently MSXML disallows "xml" from being used as a "namespace", for
> example: "xml:foo" since this seems to be the way the XML spec is heading
> with "xml:space" and "xml:lang".  So is the above paragraph just a little
> too restrictive and should it include the colon ?  If not then the following
> very common XML example is illegal:
>         <XML>
>                 This is a test.
>         </XML>
> Tim Bray's web site (http://www.xml.com/axml/axml.html) says explicitly that
> "xmlu" is an illegal name, but James Clark's expat seems to allow this ??
> Can the XML spec gurus clarify this paragraph ? Thanks.

I would say this is an "error" as defined in 1.2 of the spec but not a
fatal error nor a violation of a validity constraint.

Your processor is therefore free to ignore it or to detect and report
it.  I think it's probably best to report this only at user option. If
tools blow up when they see such names, it's going to cause problems if
future versions of XML make use of these names.  For example, I don't
want my XML processor to complain because I'm using an xml:stylesheet
PI, although it would be nice to have a "pedantic" option to tell me
that this is strictly an error (until such time as this gets licensed by
the XML spec).


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