xml-dev - Re: Possible changes for XML 2nd Edition

["David Brownell" <david-b@pacbell.net>]

> I do not see any reason to rule out fragment identifiers in system
identifiers.
> There are lots of potential uses for them. Consider:

Compatibility is such a reason.  Removing that contraint would
create a non-interoperable class of "XML 1.0" (not!) documents:


> * Grabbing a piece of an XML document to embed in another (a whole object
> that is text/xml or application/xml, cannot generally be referenced as a
> non-NDATA entity (since it includes the DOCTYPE, at least if it's valid).

Making XML 1.0 dependent on something analagous to XPath, which
creates a circular dependency (yeech).


> * A URI could point to a zip or tar archive, and the fragment identifier
> may specify a particular XMl file out of the archive.

Having that level of intelligence about URI processing seems better
suited to something like XInclude.


> * A URI could point to a big XML document that serves only to collect a
lot
> of modular fragments for re-use: such as the tables of FAA-mandated
warning
> text used in aircraft manuals.

Or, each warning could have a unique URI.  Makes it a lot easier to
maintain the warnings, under many development models, as well as to
process them (just read one little file, not a monstrous compendium).


> * system identifiers can be used for lots of other things, like DTDs
(later
> presumably schemas), and data in all kinds of notations.

XML 1.0 doesn't address schemas, they're out of scope.

I could see notations having fragment IDs though, since they're
never interpreted directly by the XML processor (application issue).


> What motivation could there be for absolutely prohibiting fragment
> identifiers?

More to the point, what motivation _was_ there?  I think simplicity
(for external entities) is a big win.

At this point, removing this constraint seems to me quite unwise.


>    It seems to me it's none of XML's business what the syntax of
> URI references is, or whether fragment identifiers are needed. What of a
> media type which defines the fragment identifier (they are media type
> specific, after all) in such a way that it ends up being *required* for
> proper interpretation

None of the text/xml or application/xml media types is so defined.
So that argument doesn't work with SYSTEM identifiers used for external
entities.

- Dave




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