I want to get informations about the used variables in an xlst script and use an own
TraceListener. I tried this:

public void enter(InstructionInfo instruction, XPathContext context) {
        StackFrame stackFrame = context.getStackFrame();
        List variables = stackFrame.getStackFrameMap().getVariableMap();

because StackFrame says "This class represents a stack frame holding details of
the variables used in a function or in an XSLT template."

But for the following script "variables" is always empty and I never get an instruction
that shows the variable!?

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0"> 
  <xsl:output method="xml" encoding="ISO-8859-1"/> 
  <xsl:template match="/">
      <xsl:variable name="title" select="/Order/Title"/> 
        <xsl:value-of select="$title"/>

best regards, marc.