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Date: Fri, 08 Sep 2006 12:21:13 +0100
From: Ross Gardler <rgardler@apache.org>
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To: dev@forrest.apache.org
Subject: Re: xinclude
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Jim Dixon wrote:
> 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

Good point.

> 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.

Does Xalan do it? This is the default parser for Forrest. A healthy 
warning in the docs and output of the validate task may be sufficient 
for those using a different parser.

> 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.

I can't see an easy way of doing this as, in many cases, the included 
content is generated by Forrest. In fact, this would be a problem if the 
parser were doing the includes.

Ross