public static ELearner getELearner(QuerySolution qs, Model model) {
   ELearner el = new ELearner();
   String uri = qs.get("?elearner").toString().trim();
   String id = model.getResource(uri).getLocalName();
   String name = qs.get("?el_name").toString().trim();
   String grade = qs.get("?el_grade").toString().trim();
   String email = qs.get("?el_email").toString().trim();
   String address = qs.get("?el_address").toString().trim();
   el.setId(id);
   el.setName(StringExchanger.getCommonString(name));
   el.setGrade(StringExchanger.getCommonString(grade));
   el.setEmail(StringExchanger.getCommonString(email));
   el.setAddress(StringExchanger.getCommonString(address));
   return el;
 }
 public String toString() {
   return id + "\t" + elearner.getId() + "\t" + resource.getRid() + "\t" + value + "\t" + datetime;
 }