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xpath ancestors

From: Chuck Jungmann <NOchuckSPAM@----.--->
To: NULL
Date: 1/9/2008 4:28:00 PM


Although I've been working with XSLT and XPATH expressions for some years, I am
occasionally stumped about why recursing back through node parents gives me funny results.
Using a named template works, using a matching template results in a stack overflow
because the the parent::node() axis of the root node is again the root node. Today, in
what seems to be a related unexpected result,  I was using the ancestor-or-self axis and
it returned an unexpected number of nodes (too many).  It seems that root node is in the
node list twice.

I've tested this in Internet Explorer, Firefox (different XML implementations) and in
oXygen using Saxon6.5.5 and all return the same results. Clearly my understanding is
lacking.  Could someone please explain to me why I should expect these results?

Thanks
Chuck Jungmann


**--- banking.xml ---**

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="banking.xsl"?>
<banking>
	<bank name="WF">
		<account name="checking"/>
		<account name="saving"/>
		<account name="mortgage"/>
	</bank>
	<bank name="BankOne">
		<account name="brokerage"/>
		<account name="creditcard"/>
	</bank>
</banking>



**-- banking.xsl --**

<?xml version="1.0"?>
<xsl:stylesheet
	version="1.0"
	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
	xmlns:html="http://www.w3.org/1999/xhtml"
	xmlns="http://www.w3.org/1999/xhtml"
	exclude-result-prefixes="html">

	<xsl:output method="xml" />

	<xsl:variable
		name="demoNode"
		select="/banking/bank[@name='WF']/account[@name='saving']" />

	<xsl:variable
		name="anc"
		select="$demoNode/ancestor-or-self::node()" />

	<xsl:template match="/">
		<html>
			<head><title>xpath demo</title></head>
			<body>
				<p>
					Expecting 3 nodes in ancestor-or-self, getting
					<xsl:value-of select="count($anc)" /> (four) instead.
				</p>
				<p>
					If I use a template to display the node list,
					I'll see "banking/banking/bank/account"
					<xsl:apply-templates select="$anc" mode="nameNode" />
				</p>
				<p>
					Using a calling a named template seems to work
					<xsl:call-template name="makePath">
						<xsl:with-param name="node" select="$demoNode" />
					</xsl:call-template>
				</p>	

				<p>
					Calling with apply-templates results in a stack-overflow:
					It seems that the root node is its own parent?!
					<!--
					<xsl:apply-templates select="$demoNode" mode="makePath" />
					-->
				</p>


			</body>
		</html>
	</xsl:template>

	<xsl:template match="node()" mode="nameNode">
		<xsl:text>--</xsl:text>
		<xsl:value-of select="name()" />
		<xsl:text>--  </xsl:text>
	</xsl:template>

	<xsl:template name="makePath">
		<xsl:param name="node" />
		<xsl:variable name="pnode" select="$node/parent::node()" />
		<xsl:if test="$pnode">
			<xsl:call-template name="makePath">
				<xsl:with-param name="node" select="$pnode" />
			</xsl:call-template>
		</xsl:if>
		<xsl:text>/</xsl:text>
		<xsl:value-of select="name($node)" />
		<xsl:if test="$node/@name">
			<xsl:text>[@name='</xsl:text>
			<xsl:value-of select="$node/@name" />
			<xsl:text>']</xsl:text>
		</xsl:if>
	<xsl:template>

	<xsl:template match="node()" mode="makePath">
		<xsl:variable name="pnode" select="parent::node()" />
		<xsl:if test="$pnode">
			<xsl:apply-templates select="$pnode" mode="makePath" />
		</xsl:if>
		<xsl:text>/</xsl:text>
		<xsl:value-of select="name()" />
		<xsl:if test="@name">
			<xsl:text>[@name='</xsl:text>
			<xsl:value-of select="@name" />
			<xsl:text>']</xsl:text>
		</xsl:if>
	</xsl:template>

</xsl:stylesheet>

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