Comparing direct ancestors

Hi List,

Thanks in advance for any help.

I've been banging my head around this problem for awhile now and could
use any advice anyone is willing to give. I have the following xml:

<?xml version="1.0"?>
<root>
	<change-begin/>
	<a>
		<p>Foo<change-end/></p>
	</a>
	<change-begin/>
	<b>
		<d>
			<t>Bar</t>
		</d>
		<d>
			<t>Foo</t>
		</d>
	</b>
	<change-end/>
	<p>Nothing <change-begin/>to worry<change-end/> about</p>
</root>

I need to write an xslt (2.0 is fine) that will "move" the
<change-begin/> and <change-end/> elements to be children of the
nearest pre-defined allowable element. So in the example above I have
<p> and <t> as elements that allow the <change-begin/> and
<change-end/> elements. The output should look like this:

<?xml version="1.0"?>
<root>
	<a>
		<p><change-begin/>Foo<change-end/></p>
	</a>
	<b>
		<d>
			<t><change-begin/>Bar</t>
		</d>
		<d>
			<t>Foo<change-end/></t>
		</d>
	</b>
	<p>Nothing <change-begin/>to worry<change-end/> about</p>
</root>

My plan was a multi-pass stylesheet that first took care of the
<change-begin/> then went on to take care of the <change-ends/>. For
brevity I've limit this post to trying to deal with the
<change-begin/>:

<?xml version='1.0'?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:variable name="allowed">
	<n>p</n>
	<n>t</n>
</xsl:variable>

<xsl:template match="/">
	<xsl:apply-templates select="root" mode="begins"/>
</xsl:template>

<xsl:template match="*" mode="begins">
<xsl:variable name="name" select="name()"/>
		<!-- ok here we narrow our field of vision -->
        <xsl:choose>
			<!-- Only worry about elements that are possible candidates for
moving changes in -->
            <xsl:when test="$allowed/n[name() = $name]">
                <xsl:choose>
					<!-- Is a sibiling a change-begin tag, or are any ancestors
siblings a change-begin tag? -->
					<xsl:when test="preceding-sibling::change-begin or
(ancestor::*[preceding-sibling::change-begin])">
						<xsl:copy>
							<change-begin/>
		                    <xsl:copy-of select="@*"/>
		                    <xsl:apply-templates mode="begins"/>
						</xsl:copy>
					</xsl:when>
					<xsl:otherwise>
		                <xsl:copy>
		                    <xsl:copy-of select="@*"/>
		                    <xsl:apply-templates mode="begins"/>
		                </xsl:copy>
					</xsl:otherwise>
                </xsl:choose>
            </xsl:when>
            <xsl:otherwise>
                <xsl:copy>
                    <xsl:copy-of select="@*"/>
                    <xsl:apply-templates mode="begins"/>
                </xsl:copy>
            </xsl:otherwise>
        </xsl:choose>
</xsl:template>

<!-- remove the begins outside of allowable elements. -->
<xsl:template match="change-begin" mode="begins">
	<xsl:if test="parent::*[name() = $allowed/n/.]">
        <xsl:copy>
            <xsl:copy-of select="@*"/>
            <xsl:apply-templates mode="begins"/>
        </xsl:copy>
	</xsl:if>
</xsl:template>

</xsl:stylesheet>

So far it doesn't work and is fast becoming a bunch of spaghetti
<choose> statements. If anyone has any ideas I would love to hear
them.

Thanks