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From Jim Dixon <...@dixons.org>
Subject Re: xinclude
Date Fri, 08 Sep 2006 11:10:41 GMT
On Fri, 8 Sep 2006, Ross Gardler wrote:

> > -------------------------------------------------------------------------
> > <!ENTITY % local.inline "|xi:include">
> > <!ENTITY % document PUBLIC
> >     "-//APACHE//ENTITIES Documentation V2.0//EN"
> >     "document-v20.dtd">
> > %document;
> >
> > <!ATTLIST document
> >   xmlns:xi CDATA #FIXED "http://www.w3.org/2001/XInclude"
> >
> > <!ELEMENT xi:include EMPTY>
> > <!ATTLIST xi:include
> >   parse     (text|xml)  "xml"
> >   href      CDATA       #REQUIRED
> >   encoding  CDATA       #IMPLIED
> >
> > -------------------------------------------------------------------------
> >
> > This works for my purposes.  I enable XInclusion by using this doctype
> > instead of document-v20.dtd.
> >
> > If this were to be done as a patch, I suppose the patch would introduce
> > a new doctype V2.1, with the xi:include element moved into what would now
> > be document-v21.mod.  This would be added to catalog.xcat.
>
> I don't think we need to create a version 2.1 for this to be honest. I
> know we *should* but it is an optional element that is 100% backward
> compatible.
>
> Can we just slip it in without causing any upset? Naughty I know, but I
> don't have the time to do a "proper job" on this.
>
> > The exact place(s) where the xi:include element would be permitted might
> > be an issue to some.  I would add it to link-content.mix.

I've thought about this a bit more.  One of the problems here is that
adding xi:include elements has unexpected results.

If the DTD is extended as above, then the validator will, I think, not
check beyond the xi:include element, and so a document may validate
even though what is being XIncluded is nonsense.  I can write
  <p><xi:include href="rubbish.xml"/></p>
and validation will succeed, because the xi:include element has the
pattern required by the DTD even though rubbish.xml isn't XML at all

The expected behavior is that the validator recognizes that what is being
XIncluded is XML (as it is by default) and goes through to validate that
as well, silently replacing the xi:include element with whatever is
XIncluded.  I think that some parsers do this - perhaps only if an
option is set - but most don't.

A better approach would be to process the XIncludes before validation,
stripping off the xlmns:xi attribute from the document element and
replacing xi:includes with whatever they resolve to.  This should be
cheaper than it might seem: unless the xmlns:xi is present, the
document is simply handed on to the validator untouched.

--
Jim Dixon  jdd@dixons.org   tel +44 117 982 0786  mobile +44 797 373 7881

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