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Re: Media types, fragment identifiers, and XPointer

I was expecting more response, but only Larry responded ;-)
#Thanks.  > Larry

Larry Masinter wrote:
> It would be good if we could extend the MIME registry of media
> types to include, where possibly, a description of how
> "fragment identifiers" apply to that media type.
> Currently this information is not in the media type registry,
> and fragment identifiers are, in practice, only used for HTML.

RFC2396 ("Uniform Resource Identifiers (URI): Generic Syntax"), which 
you co-authored, says:

   The semantics of a fragment identifier is a property of the data
   resulting from a retrieval action, regardless of the type of URI used
   in the reference.  Therefore, the format and interpretation of
   fragment identifiers is dependent on the media type [RFC2046] of the
   retrieval result.  The character restrictions described in Section 2
   for URI also apply to the fragment in a URI-reference.  Individual
   media types may define additional restrictions or structure within
   the fragment for specifying different types of "partial views" that
   can be identified within that media type.

   A fragment identifier is only meaningful when a URI reference is
   intended for retrieval and the result of that retrieval is a document
   for which the identified fragment is consistently defined.

text/html is defined by RFC1866 (HTML 2.0).  HTML 2.0 and its subsequent 
versions define the interpretation of fragment identifiers.  

There appear to be no information in the media type registry, which is:

> To make this useful might mean some extensions to current
> platform definitions of MIME dispatch (to pass along the
> fragment identifier to the media type rendering agent), but

RFC 2045 says:

   The purpose of the Content-Type field is to describe the data
   contained in the body fully enough that the receiving user agent can
   pick an appropriate agent or mechanism to present the data to the
   user, or otherwise deal with the data in an appropriate manner. The
   value in this field is called a media type.

Fragment identifiers are not mentioned by RFC 2045 or RFC 2046.

Are there any documents about generalization of fragment identifiers?  
I suppose that there is no such.

> it was desirable to have named or identified components for
> other types. If there's a general definition of how this
> works for XML types that aren't otherwise specified, that's
> great, too. 

Here are some questions about requirements.

Q1.  Do we need XPointers for every XML instance?  

I personally think that this is too much.  For example, I do not think we have 
use XPointers for RDF, which is in the XML syntax.

Q2.  Do we need XPointers only for human-readable documents that are rendered 
     by some browsers?

I am not sure if the answer is Yes.  How do XLL experts in this ML feel?


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