code: private char getRelationFromStringMatchers(String sourceLabel, String targetLabel) {
          char relation = IMappingElement.IDK;
          int i = 0;
          while ((relation == IMappingElement.IDK) && (i < stringMatchers.size())) {
              relation = stringMatchers.get(i).match(sourceLabel, targetLabel);
              i++;
          }
          return relation;
      }
docs: Returns semantic relation holding between two labels as computed by string based matchers.
  
  @param sourceLabel the string of the source label
  @param targetLabel the string of the target label
  @return semantic relation holding between two labels as computed by string based matchers