non-authoritative syntaxes for fragment identifiers

Hello,

The issue I would like to submit here is the following: Does the use of 
a non-authoritative fragment identifier syntax make a URI invalid? In 
relation to this problem, I have a suggestion for the Last Call on 
RFC2396bis.

In the AWWW document, Paragraph 4 of clause 3.3 specifies:

"Parties that draw conclusions about the interpretation of a fragment 
identifier based solely on a syntactic analysis of all or part of a URI 
do so at their own risk; such interpretations are not authoritative 
because they are not licensed by specification."

This clause seems to allow the use of a non-authoritative fragment 
syntax although there is no guarantee it can always be processed. I 
think it is reasonable to allow the use of non-authoritative fragment 
syntaxes, especially considering that:

- although in some cases Internet media types owners may not need/want 
to define a syntax, content owners may want to address fragments of 
content, and have to define non-authoritative syntaxes,
- in the future, it may be beneficial to establish common conventions 
for addressing fragments consistently across multiple representations of 
a content. Indeed at the moment, very few Internet media types have 
defined a syntax for fragment identifiers.

At the moment, both the RFC2396bis and the AWWW specify that:

The semantics of a fragment identifier are defined by the set of
   representations that might result from a retrieval action on the
   primary resource.  The fragment's format and resolution is therefore
   dependent on the media type [RFC2046] of a potentially retrieved
   representation, even though such a retrieval is only performed if the
   URI is dereferenced.

This does not clearly state whether the use of a non-authoritative 
scheme is valid or not. Another situation could happen if a 
non-authoritative fragment syntax is widely used on the web for a 
particular representation and later on an Internet media type owner 
registers a fragment syntax. Both schemes could potentially coexist and 
be deployed assuming that the syntaxes use a mechanism to help the 
processor identify which scheme applies (for instance using a scheme 
name as for the Xpointer Framework).

If the use of non-authoritative fragment identifier syntaxes in URIs is 
allowed, although at the user's own risk, such URIs should be valid. 
Therefore, I suggest that RFC2396bis clarifies whether a URI with 
non-authoritative fragment identifier is still a valid URI or not.

Best regards
Myriam