code: public String getRdfaAttr() {
  
          String result = "";
          CmsObject cms = obtainCmsObject();
          if (cms != null) {
              if (isDirectEditEnabled(cms)) {
                  if (m_contentValue != null) {
                      // within the offline project return the OpenCms specific entity id's and property names
                      result = CmsContentService.getRdfaAttributes(m_contentValue);
                  } else if ((m_nullValueInfo != null)) {
                      if (m_nullValueInfo.getParentValue() != null) {
                          result = CmsContentService.getRdfaAttributes(
                              m_nullValueInfo.getParentValue(),
                              m_nullValueInfo.getValueName());
                      } else if (m_nullValueInfo.getContent() != null) {
                          result = CmsContentService.getRdfaAttributes(
                              m_nullValueInfo.getContent(),
                              m_nullValueInfo.getLocale(),
                              m_nullValueInfo.getValueName());
                      }
                  }
              } else {
                  // TODO: return mapped property names etc. when online
              }
          }
          return result;
      }
docs: Returns the RDF annotation to this content value.<p>
  
  Use to insert the annotation attributes into a HTML tag.<p>
  Example using EL: &lt;h1 ${value.Title.rdfaAttr}&gt;${value.Title}&lt;/h1&gt; will result in
  &lt;h1 data-oc-id="..." data-oc-field="..."&gt;My title&lt;/h1&gt;<p>
  
  @return the RDFA