Namespace problem

I'm working on a stylesheet to process an XML (WSDL) file where some of the 
attribute are QNames. I need to separate the QName in the namespace URI and 
the local name. I'm having trouble resolving the correct namespace URI.
I have the following template which is producing the wrong value for the 
attribute portType_nspc.
        <xsl:template match="wsdl:operation">
                <xsl:element name="operation">
                        <xsl:choose>
                                <xsl:when 
test="contains(parent::node()/@name,':')">
                                        <xsl:attribute name="portType_nspc">
                                                <xsl:choose>
                                                        <xsl:when 
test="contains(parent::node()/@name,':')">
								<xsl:value-of 
select="namespace::*[starts-with(name(),substring-before(parent::node()/@name,':'))]"/>
                                                        </xsl:when>
                                                        <xsl:otherwise>
                                                                <xsl:value-of 
select="ancestor::*[last()]/@targetNamespace"/>
                                                        </xsl:otherwise>
                                                </xsl:choose>
                                        </xsl:attribute>
                                </xsl:when>
                                <xsl:otherwise>
                                        <xsl:attribute name="portType_nspc"/>
                                </xsl:otherwise>
                        </xsl:choose>
                </xsl:element>
        </xsl:template>

when run on the following document

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://schemas.xmlsoap.org/wsdl/"; name="TemperatureService"
        targetNamespace="http://www.xmethods.net/sd/TemperatureService.wsdl";
        xmlns:tns="http://www.xmethods.net/sd/TemperatureService.wsdl";>
        <portType name="tns:TemperaturePortType">
                <operation name="tns:getTemp">
                        <input message="tns:getTempRequest"/>
                        <output message="tns:getTempResponse"/>
                </operation>
        </portType>
</definitions>

I'm getting

        <operation portType_nspc="http://www.w3.org/XML/1998/namespace"/>

when I expect to get

	<operation 
portType_nspc="http://www.xmethods.net/sd/TemperatureService.wsdl"/>
I've tried it with several different versions of Xalan (both C++ and Java 
versions) and get the same results.
Any ideas as to what is going wrong?

Marc