Xalan Porting Problem

[Marco]

Hallo,
I'm trying to porting an old application which uses an old version of 
Xalan to a newer which uses Xalan  2.6.0.
That old application  instantiates an XSLTEngine object in a servlet 
Java, then passes this object as parameter to a stylesheet.
The code that  does this is:

               try {
                   this.xsltproc.reset();
                   this.xsltproc.setTraceSelect(true);
                   this.xsltproc.setTraceTemplates(true);
                   this.xsltproc.setDiagnosticsOutput(System.out);
                   this.xsltproc.setStylesheetParam("ttdb", _xslteng);
                   this.xsltproc.process(new XSLTInputSource(doc),
                                new XSLTInputSource(xsltfile),
                                new XSLTResultTarget(xml_sink));
               } catch(SAXException e) {
                   docerr = -1;
                   docerrtext = "Error processing Stylesheet : " + 
e.getMessage();
                   System.out.println("ttprocessor servlet: could not 
process request. Error processing                             Stylesheet");
                   System.out.println("exception is " + 
e.getMessage());                           
               }

where _xslteng is an XObject created passing the XSLTEngine object to 
XObject constructor, and xsltproc is an object of type 
org.apache.xalan.xslt.XSLTProcessor (which doesn't exixst in Xalan 
2.6.0.??????.......)

Now, I use the following code:
            Transformer transformer;
           try
           {
               Templates templates = factory.newTemplates(new 
StreamSource(new File(xsltfile)));
               transformer = templates.newTransformer();
               transformer.setParameter("ttdb", xslteng);
               DOMResult res = new DOMResult();
               transformer.transform(new DOMSource(doc), res);
            }
........................................................
Where xslteng is an object of type ttdblib.XSLTEngine

The xsl file is:
       <?xml version="1.0" encoding="UTF-8" ?>
       <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
                       xmlns:java="http://xml.apache.org/xalan/java";
               xmlns:eng="xalan://ttdblib.XSLTEngine"
                       version='1.0'>
   
       <xsl:param name="ttdb"/>
       <xsl:template match="/">
           <xsl:apply-templates select="/message/OrdinativoImbarco"/>
       </xsl:template>
           <xsl:template match="OrdinativoImbarco">
               <xsl:variable name="valore" select="eng:prova($ttdb)"/>
                   <p>Valore: <xsl:value-of select="string($valore)"/></p>
            </xsl:template>

       </xsl:stylesheet>
When I run that program, I receive an error like this:
'METHOD_NOT_FOUND_ERR ttdblib.XSLTEngine:prova'
The method prova is public in the class XSLTEngine, and it returns a string.