Summary If you are really going to get nitty and gritty, this sample does without the sum() function

Additional information

<!--Main.xsl--> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <xsl:call-template name="sum"> <xsl:with-param name="pList" select="orders/*"/> </xsl:call-template> </xsl:template> </xsl:stylesheet> <!--sum.xsl--> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:sum-fold-func="sum-fold-func" exclude-result-prefixes="xsl sum-fold-func" > <xsl:import href="foldl.xsl"/> <sum-fold-func:sum-fold-func/> <xsl:template name="sum"> <xsl:param name="pList" select="/.."/> <xsl:variable name="sum-fold-func:vFoldFun" select="document('')/*/sum-fold-func:*[1~"/> <xsl:call-template name="foldl"> <xsl:with-param name="pFunc" select="$sum-fold-func:vFoldFun"/> <xsl:with-param name="pList" select="$pList/@uprice"/> <xsl:with-param name="pA0" select="0"/> </xsl:call-template> </xsl:template> <xsl:template name="add" match="*[namespace-uri() = 'sum-fold-func'~"> <xsl:param name="arg1" select="0"/> <xsl:param name="arg2" select="0"/> <xsl:value-of select="$arg1 + $arg2"/> </xsl:template> </xsl:stylesheet> <!--foldl.xsl--> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template name="foldl"> <xsl:param name="pFunc" select="/.."/> <xsl:param name="pA0"/> <xsl:param name="pList" select="/.."/> <xsl:choose> <xsl:when test="not($pList)"> <xsl:copy-of select="$pA0"/> </xsl:when> <xsl:otherwise> <xsl:variable name="vFunResult"> <xsl:apply-templates select="$pFunc[1~"> <xsl:with-param name="arg0" select="$pFunc[position() > 1~"/> <xsl:with-param name="arg1" select="$pA0"/> <xsl:with-param name="arg2" select="$pList[1~"/> </xsl:apply-templates> </xsl:variable> <xsl:call-template name="foldl"> <xsl:with-param name="pFunc" select="$pFunc"/> <xsl:with-param name="pList" select="$pList[position() > 1~"/> <xsl:with-param name="pA0" select="$vFunResult"/> </xsl:call-template> </xsl:otherwise> </xsl:choose> </xsl:template> </xsl:stylesheet>