code: public int getElementPosition(String element_id) {
  		int index = -1;
  		for (int i = 0; i < entities.size(); i++) {
  			QueryControllerEntity element = entities.get(i);
  
  			if (element instanceof QueryControllerQuery) {
  				QueryControllerQuery query = (QueryControllerQuery) element;
  				if (query.getID().equals(element_id)) {
  					index = i;
  					break;
  				}
  			}
  
  			if (element instanceof QueryControllerGroup) {
  				QueryControllerGroup group = (QueryControllerGroup) element;
  				if (group.getID().equals(element_id)) {
  					index = i;
  					break;
  				}
  				else {
  					// Searching inside the group.
  					Vector<QueryControllerQuery> queries_ingroup = group.getQueries();
  					for (QueryControllerQuery query : queries_ingroup) {
  						if (query.getID().equals(element_id)) {
  							index = i;
  							break;
  						}
  					}
  				}
  			}
  		}
  		return index;
  	}
docs: Returns the index of the element in the vector. If its is a query and the
  query is found inside a query group. The position of the group is
  returned instead.