Hi there, In my application I have this method: public static String getAllPartsAsTree(String a) throws XQException, XQQueryException { XQConnection con = Connection.getConnection(); XQExpression xqe = con.createExpression(); xqe.bindString(new QName("b"), a, null); String xqueryString = "import module namespace lib=\" http://www.example.com/library_module\";" + "declare option output:method \"xhtml\";" + "declare variable $b external; " + "lib:gethtml($b)"; XQResultSequence rs = xqe.executeQuery(xqueryString) ; String b = rs.getSequenceAsString(null); con.close(); return b; } When I run the app I get the following error message: Exception in thread "main" javax.xml.xquery.XQException: The prefix "output" is unknown in this static context. I can't understand how to interpret the error message. The same query in BaseXGUI works perfectly. I hope someone can help me. Thanks!