OSLC ValidatedBy bidirectional link

I created OSLC ValidatedBy link Requirement to TestCase using function below from Example04.java but link is unidirectional how can i make it bidirectional. Link shows in RRC but not in RQM 'Validates Requirements'.

    private void updateRequirement(String requirementURL, String testcaseURL) throws Exception {
        //Get the document
        HttpGet query = new HttpGet(requirementURL);
        query.addHeader("Accept", "application/xml");
        query.addHeader("OSLC-Core-Version", "2.0");       

        HttpResponse response = HttpUtils.sendGetForSecureDocument(RM_server,
                query, login, password, httpclient, RM_JTS_Server);
       
        if (response.getStatusLine().getStatusCode() != 200) {
            response.getEntity().consumeContent();
            throw new HttpResponseException(response.getStatusLine()
                    .getStatusCode(), response.getStatusLine()
                    .getReasonPhrase());
        }
       
        // Retrieve the designated Service Provider
        InputSource source = new InputSource(response.getEntity().getContent());
        Document doc = parse(source);
        response.getEntity().consumeContent();
        Header etag = response.getLastHeader("etag");
       
        //Add a link, with DOM
        NodeList elementsByTagName = doc.getDocumentElement().getElementsByTagName("oslc_rm:Requirement");
        if (elementsByTagName.getLength() == 1){
            Element req = (Element)elementsByTagName.item(0);
            //Note: You can only add links for OSLC link types,
            //Check the OSLC RM V2 specification for a list of available types
            // http://open-services.net/bin/view/Main/RmSpecificationV2?sortcol=table;table=up#Resource_Requirement
            Element validatedBy = doc.createElement("oslc_rm:validatedBy");
            validatedBy.setAttribute("rdf:resource", testcaseURL); //Any valid url can be added
            req.appendChild(validatedBy);
        }
       
        //Write out our content then do a PUT
        Transformer transformer = TransformerFactory.newInstance().newTransformer();
        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes"); //$NON-NLS-1$
        transformer.setOutputProperty(OutputKeys.INDENT, "no"); //$NON-NLS-1$
        transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8"); //$NON-NLS-1$
        StreamResult result = new StreamResult(new StringWriter());
        transformer.transform(new DOMSource(doc), result);
        String newContent = result.getWriter().toString();
        System.out.println("Modified Requirement Content ->>\n" + newContent);
       
        //Do the PUT
        HttpPut put = new HttpPut(requirementURL);
        put.addHeader("Accept", "application/xml");
        put.addHeader("Content-Type", "application/xml");
        put.addHeader("OSLC-Core-Version", "2.0");
        if ( etag != null) {
            put.addHeader("If-Match", etag.getValue());
        }
        put.setEntity(new StringEntity(newContent, HTTP.UTF_8));
        response = HttpUtils.sendPutForSecureDocument(RM_server, put, login, password, httpclient, RM_JTS_Server);
        response.getEntity().consumeContent();
        if (response.getStatusLine().getStatusCode() != 200) {
            throw new HttpResponseException(response.getStatusLine()
                    .getStatusCode(), response.getStatusLine()
                    .getReasonPhrase());
        }
        //If we get here then our PUT succeeded and the requirement should have our link now
    }