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RE: Summary: xml:lang validity and RFC 1766 refs to outdated code s

• From: Mike Brown <mbrown@c...>
• To: 'John Cowan' <jcowan@r...>
• Date: Tue, 08 Aug 2000 13:06:40 -0600

[I'm removing the Unicode list from the recipients]

>	<span xml:lang="roa">Yn nediwn seint yn llinghedig,
>		yn nediwn seint yn cor</span>
>
> is not proper XML, although it is well-formed
> [...]
> > It seems that XML says I must use them, but it would not
> > a violation of validity if I didn't use them.
> 
> It is a violation of the intent of the xml:lang attribute
> not to use them.
> 
> > It doesn't necessarily follow that xml:lang values can
> > avoid conforming to RFC 1766.
> 
> They cannot avoid it.

Hmm, how's this for a reconciliation, then...

There are 3 sets of rules at work, here:

1. XML processor-enforced rules of well-formedness that do not hold xml:lang
values to any requirements that are different from other attributes;

2. Validating XML processor-enforced constraints on validity, for which
there is no binding language in the XML spec for xml:lang values; and

3. Optionally enforced rules that are neither well-formedness nor validity
constraints, but that satisfy certain intentions, so that document authors
can produce "proper" XML. Rules of this type which are broken do not change
a document's  XML 1.0 conformance status.

The statement that xml:lang values are RFC 1766 (and successors) language
identifiers falls under number 3. (correct?) And the normative reference to
RFC 1766 and its successors means that the rules for constructing "proper"
language identifiers are described in those documents. As long as those RFCs
say so, in typical cases this will result in the use of certain ISO lists of
language and country codes.

A similar example is found in the requirement by the Namespaces in XML
Recommendation that xmlns attribute values be URIs as defined by RFC 2396.
This is not held as a requirement for conformance to the Recommendation, for
well-formedness, nor for validity. <myDoc xmlns:wink=";-)"/> would be
improper but no XML processor would be required (by the specs) to complain
about it.

Is this correct?

IMHO, the way these subtleties are expressed in the language of the specs
make XML frustrating not only for document authors, but also for people in a
position of teaching others how to author XML documents. "Rules that are not
or cannot be easily enforced, but that you have to follow anyway" :)

-Mike

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