RE: Streaming basically impossible in the face of XPointers

It appears to be impossible to improve streamability without removing
functionality from XInclude.  The WG decided instead to bless a kind of
"streamable subset" by adding text along these lines:

_______
The abscense of a value for the href attribute, either by the appearance
of href="" or by the absence of the href attribute, represents a case
which may be incompatible with certain implementation strategies. For
instance, an XInclude processor might not have a textual representation
of the source infoset to include as parse="text", or it may be unable to
access another part of the document using parse="xml" and an xpointer
because of streamability concerns. An implementation may choose to treat
any or all absences of a value for the href attribute as resource
errors. Implementors should document the conditions under which such
resource errors occur.
_______

We hope this is an acceptable resolution of your concern.

> -----Original Message-----
> From: www-xml-xinclude-comments-request@w3.org
[mailto:www-xml-xinclude-
> comments-request@w3.org] On Behalf Of Elliotte Rusty Harold
> Sent: Monday, January 26, 2004 8:36 AM
> To: www-xml-xinclude-comments@w3.org
> Subject: Streaming basically impossible in the face of XPointers
> 
> 
> This has been brought up before, but a recent test case raised by
> Jonathan Marsh indicated that the problem was worse than I had
> thought. An XPointer without an href part can point iunto the same
> document. For exxample,
> 
> <root>
>    <element id="bar"/>
>    <xi:include xpointer="bar"/>
> </root>
> 
> Since XPointers can point forwards and backwards this means that even
> a minimally conforming implementation has to keep the entire document
> in memory until it has been completely processed. Furthermore, even a
> tree-based implementation can't modify a document in place because it
> may need to resolve XPointers that refer to the original, unmodified
> document.
> 
> As an implemennter, I see no plausible way to handle XPointers in
> SAX, and even in tree-based APIs like XOM (and presumably other
> tree-based APIs) it's very tough. XPointers are an implementation
> dependance conformance issue to start with because some
> implementations support the xpointer scheme, some don't, and some
> support it partially. However, a lot of use cases don't require
> XPointers at all.  I wonder if it would be better if they were
> removed completely?
> --
> 
>    Elliotte Rusty Harold
>    elharo@metalab.unc.edu
>    Effective XML (Addison-Wesley, 2003)
>    http://www.cafeconleche.org/books/effectivexml
> 
>
http://www.amazon.com/exec/obidos/ISBN%3D0321150406/ref%3Dnosim/cafeaula
it
> A
>

Received on Wednesday, 25 February 2004 18:53:36 UTC