Hello,
I am getting an error when performing a transformation. Both the xml and xsl files are otherwise well-formed. Getting the following error:

Error in XPath expression, Not a node set

at the following point in xsl file

<xsl:if test="$packageCount[. > 0]">

Here is more surrounding context:

<xsl:template name="rolledUpChildren">
        <xsl:param name="childNodes"/>
        <xsl:param name="packageCount"/>
        <xsl:param name="actorCount"/>
        <xsl:param name="useCaseCount"/>
        <xsl:param name="activityCount"/>
        <xsl:if test="count($childNodes) > 0">
            <xsl:call-template name="rolledUpChildren">
                <xsl:with-param name="childNodes" select="$childNodes/ownedMember"/>
                <xsl:with-param name="packageCount" select="$packageCount + count($childNodes[@xsi:type='uml:Package'])"/>
                <xsl:with-param name="actorCount" select="$actorCount + count($childNodes[@xsi:type='uml:Actor'])"/>
                <xsl:with-param name="useCaseCount" select="$useCaseCount + count($childNodes[@xsi:type='uml:UseCase'])"/>
                <xsl:with-param name="activityCount" select="$activityCount + count($childNodes[@xsi:type='uml:Activity'])"/>
            </xsl:call-template>
        </xsl:if>
        <xsl:if test="count($childNodes) = 0">
            <b>
                <xsl:if test="@xsi:type='uml:Package'">
                    <xsl:if test="$packageCount[. > 0]">
                        <xsl:call-template name="indent1"/>Packages:
            <xsl:value-of select="$packageCount"/>
                    </xsl:if>
                    <xsl:if test="$actorCount[. > 0]">
                        <xsl:call-template name="indent1"/>Actors:
            <xsl:value-of select="$actorCount"/>
                    </xsl:if>
                    <xsl:if test="$useCaseCount[. > 0]">
                        <xsl:call-template name="indent1"/>UseCases:
            <xsl:value-of select="$useCaseCount"/>
                    </xsl:if>
                    <xsl:if test="$activityCount[. > 0]">
                        <xsl:call-template name="indent1"/>Activities:
            <xsl:value-of select="$activityCount"/>
                    </xsl:if>
                </xsl:if>
                <xsl:if test="@xsi:type='uml:Model'">
                    <xsl:if test="$packageCount[. > 0]">
                        <xsl:call-template name="indent1"/>Packages:
            <xsl:value-of select="$packageCount"/>
                    </xsl:if>
                    <xsl:if test="$actorCount[. > 0]">
                        <xsl:call-template name="indent1"/>Actors:
            <xsl:value-of select="$actorCount"/>
                    </xsl:if>
                    <xsl:if test="$useCaseCount[. > 0]">
                        <xsl:call-template name="indent1"/>UseCases:
            <xsl:value-of select="$useCaseCount"/>
                    </xsl:if>
                    <xsl:if test="$activityCount[. > 0]">
                        <xsl:call-template name="indent1"/>Activities:
            <xsl:value-of select="$activityCount"/>
                    </xsl:if>
                </xsl:if>
            </b>
        </xsl:if>
    </xsl:template>

Interestingly (or not..), I do not get this error when transformation is against newer version of XMLSPY (2007 sp2), but do against older (version 5 rel 2). Thanks for any help.

It's complaining that $packageCount isn't a node-set (and therefore, in XSLT 1.0, can't be filtered). So you need to look for the calling code that sets this parameter. Perhaps it doesn't set the parameter, in which case $packageCount will be a zero-length string.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

Michael, oh, sort of like a null string I guess in compiled languages parlance. How do I check for zero-length or null string? Thanks so much.

Michael, thank you for assistance. I check the length now ahead of the XPath expression.

There's no such thing as a null string in XPath. You can test for a zero-length string with test="$x=''". But you need to be looking at the code that calls this template to see what value it supplies for this parameter.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference