code: public void validate(final VAlarm target) throws ValidationException {
          /*
           * ; the following are all REQUIRED,
           * ; but MUST NOT occur more than once action / description / trigger / summary
           * ; the following is REQUIRED,
           * ; and MAY occur more than once attendee /
           * ; 'duration' and 'repeat' are both optional,
           * ; and MUST NOT occur more than once each,
           * ; but if one occurs, so MUST the other duration / repeat /
           * ; the following are optional,
           * ; and MAY occur more than once attach / x-prop
           */
          Arrays.asList(DESCRIPTION, SUMMARY).forEach(property -> PropertyValidator.getInstance().assertOne(property, target.getProperties()));
  
          PropertyValidator.getInstance().assertOneOrMore(ATTENDEE, target.getProperties());
      }
docs: {@inheritDoc}