Something

<!-- THE XML FILE -->
<root>

<title>An Addition</title>

<calculation>

<sum first="5" second="7"></sum>

</calculation>

</root>





<!-- THE XSLT FILE -->
<xsl:stylesheet	version="1.0"

	xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

	<xsl:output method="xml" indent="yes"/>



	<xsl:template name="addition">

		<xsl:param name="p1"/>

		<xsl:param name="p2"/>

			<xsl:value-of select="$p1+$p2"/>

	</xsl:template>




<xsl:template name="//sum">

			<xsl:attribute name="result">

				<xsl:call-template name="addition">

				<xsl:with-param name="p1" select="@first"/>

				<xsl:with-param name="p2" select="@second"/>

				</xsl:call-template>

			</xsl:attribute>

</xsl:template>



	<xsl:template match="/">

	<xsl:copy-of select="*">		

<xsl:apply-templates select="//sum"/>	

	</xsl:copy-of>



	</xsl:template>

</xsl:stylesheet>