public InsertObservationParameters(
     final ObservationParameters observationParameters, final Collection<String> offerings)
     throws IllegalArgumentException {
   if (observationParameters == null
       || observationParameters.isEmpty()
       || !observationParameters.isValid()) {
     throw new IllegalArgumentException(
         "Parameter 'ObservationParameters' is required and may not be null or empty!");
   }
   addNonEmpty(INSERT_OBSERVATION_OFFERINGS_PARAMETER, offerings);
   mergeWith(observationParameters);
   observation = observationParameters;
 }
 public boolean isValid() {
   return !isEmptyValue(INSERT_OBSERVATION_OFFERINGS_PARAMETER) && observation.isValid();
 }