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Re: Conformance value of "+xml"?

Dan Kohn wrote:

> The concern with fragment identifiers was that certain media types developed
> before the XLink spec (I remember SVG being mentioned),

SVG was developed concurrently with the XLink spec and is, in fact, the
first W3C specification to use XLink.

However, since you mention fragment identifiers, I suspect you were
thinking of XPointer? SVG supports a subset of XPointer, not the ful spec.

>  might not confirm to
> the later linking spec.  If all it takes to conform to the linking spec is
> to be valid XML, 

No, conformance to XLink requires use of the XLink spec (which SVG for
example does); conformance to XPointer requires an application to conform
to XPointer, and cannot be inferred from looking at the content that is
being pointed into.

> Let me close by quoting the RFC 2119 definitions for MUST and SHOULD, to
> point out that the distance between them is really quite large.  We worked
> hard to only use MUST when interoperability guarantees demanded it:

I think it was interoperability guarantees that Mark was looking for.
However, the point about non-XML applcations MUST NOT be registered with a
+xml suffix seems to at least guarantee that the message body will be a
well formed XML instance.

> For the fifth paragraph I'd recommend changing the wording to reflect
> that for fragment identifiers at least, registrations are free to
> *extend* the syntax, but must at least support the XML syntax;

In the case of SVG, since there seemed to be little prior experience with
the full complexities of XPoinbter, SVG supports a subset of the syntax. So
the uses in an  SVG instance will all conform to the XPointer spec, but the
converse is not true - not all valid XPointers are guaranteed to be
processd by SVG-aware user agents.