If your stylesheet contains
<xsl:call-template name="pmml:ItemRef">
then there must be a template declared with
<xsl:template name="pmml:ItemRef">
Declaring it as
<xsl:template match="pmml:ItemRef">
won't work. However, it's possible for a template to have both a match attribute and a name attribute.
Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference