code: public void addValidator(Schema schema, ModeUsage modeUsage) {
        // adds the schema to this section schemas
        schemas.addElement(schema);
        // creates the validator
        Validator validator = createValidator(schema);
        // adds the validator to this section validators
        validators.addElement(validator);
        // add the validator handler to the list of active handlers
        activeHandlers.addElement(validator.getContentHandler());
        // add the mode usage to the active handlers attribute mode usage list
        activeHandlersAttributeModeUsage.addElement(modeUsage);
        // compute the attribute processing
        attributeProcessing = Math.max(attributeProcessing,
                                       modeUsage.getAttributeProcessing());
        // add a child mode with this mode usage and the validator content handler
        childPrograms.addElement(new Program(modeUsage, validator.getContentHandler()));
        if (modeUsage.isContextDependent())
          contextDependent = true;
      }
docs: Adds a validator.
  @param schema The schema to validate against.
  @param modeUsage The mode usage for this validate action.