code: static Integer parseTimeConstraint(Instance instance, String constraint,
              ConnectionManager cm) throws KnowledgeSourceReadException {
          Integer constraintValue = null;
          if (instance != null && constraint != null) {
              constraintValue = (Integer) cm.getOwnSlotValue(instance,
                      cm.getSlot(constraint));
          }
  
          return constraintValue;
      }
docs: Calculates a time constraint in milliseconds from a pair of time
  constraint and units values in a Protege instance.
  
  @param instance a Protege <code>Instance</code> object.
  @param constraint a time constraint slot name. The named slot is expected
  to have an Integer value.
  @param constraintUnits a time constraint units slot name. May have the
  values "Minute", "Hour", or "Day".
  @return a <code>Weight</code> object representing a time in milliseconds.