__log.debug("Compiling expression " + xpathStr);
XPathFactory xpf = new XPathFactoryImpl();
JaxpFunctionResolver funcResolver = new JaxpFunctionResolver(
_compilerContext, out, source.getNamespaceContext(), _bpelNS);
JaxpVariableResolver varResolver = new JaxpVariableResolver(_compilerContext, out);
XPath xpe = xpf.newXPath();
xpe.setXPathFunctionResolver(funcResolver);
xpe.setXPathVariableResolver(varResolver);
xpe.setNamespaceContext(source.getNamespaceContext());
XPathExpression expr = xpe.compile(xpathStr);
// evaluate the expression so as to initialize the variables