Re: XPointer (was Re: XInclude vs SAX vs validation)

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

Daniel wrote:
> > The gap from SAX to XPath or XPointer is probably like going from assembly
> > to Lisp or Prolog, it's a lot but it should not stop people needing high
> > level tools.

However, nobody should then be positioning such tools
using XPointer as "low level" general purpose tools, the
way XInclude does.

There are two obvious ways to fix that positioning:
drop XPointer, or admit it's a "high level" tool that
applies some hypertext models to XML.


Simon responded:
> I don't grasp what you're saying here.  Mixing assembler and C and even
> Java isn't that difficult. Supporting all of XPath in a SAX framework
> seems largely impossible.

... without first implementing an expensive DOM-like representation of
the infoset data, which can be an anti-goal.  Using Daniel's earlier example
of a 200 MB document, the rule of thumb is that the DOM-ish version
of that infoset data is going to cost  about 2 GB of virtual memory, which
is rather contrary to SAX-ish system goals.

It'd have been different if XPointer were _only_ the "streamable subset"
of XPath that Daniel mentioned, but I don't believe that's how it stands.

- Dave