code: public void addRoleRelation(String roleFrom, String roleTo) throws PropertyException{
  		validateStringValue(roleFrom);
  		validateStringValue(roleTo);
  		
  		String relationName = String.format(ROLE_RELATION_FORMAT, getNextRelationIndex());
  		props.setProperty(relationName, String.format(ROLE_RELATION_VALUE_FORMAT, roleFrom, roleTo));
  		addRelationNameToList(relationName);
  	}
docs: -- Role relations