slow xsltproc XInclude processing w/complex document?

Subject: slow xsltproc XInclude processing w/complex document?
From: Paul DuBois <paul@xxxxxxxxxxxx>
Date: Tue, 6 Jul 2004 14:58:42 -0500
I've been running some tests on a document that includes nested
Xinclude directives. The document is complex: upwards of 1500 files,
nested to a depth of up to 4 levels.  Total size of content is about 4.8MB.

For simple testing, I'm attempting only to produce a "flattened"
document that just resolves the XIincludes.  Stylesheet looks like

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="";>

<!-- Identity transform, but "flatten" xincludes -->

<xsl:output method="xml" indent="yes"/>
<xsl:preserve-space elements="*"/>

<xsl:template match="xi:include" xmlns:xi="";>
  <xsl:for-each select="document(@href)">

<!-- identity transform -->

<xsl:template match="/ | node() | @* | comment() | processing-instruction()">
    <xsl:apply-templates select="@* | node()"/>


My processing command is:

xsltproc --xinclude --novalid xinclude.xsl input.xml > output.xml

This takes about 12 minutes on my 900 MHz G3 iBook (Mac OS X), and about
4 minutes on my 2.8 GHz Pentium 4 Gentoo Linux box.

That seems pretty slow, particular given that the control condition takes
mere seconds (running the flattenedly document through a standard identity
transform with xsltproc).

I don't want to post the input here because it's so big, so this is really
just a preliminary post to ask for advice as to how I might go about
improving the XInclude-d transform: Is this a known issue with
xsltproc/XInclude?  Or is there perhaps some flag I should be using that I
am failing to use?  Something bad about my stylesheet?

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