protected void xscalarCondition(
     String function, SubQuery<ServiceRankCB> subQuery, String operand) {
   assertObjectNotNull("subQuery<ServiceRankCB>", subQuery);
   ServiceRankCB cb = new ServiceRankCB();
   cb.xsetupForScalarCondition(this);
   subQuery.query(cb);
   String subQueryPropertyName = keepScalarCondition(cb.query()); // for saving query-value.
   registerScalarCondition(function, cb.query(), subQueryPropertyName, operand);
 }