code: public void addInvalidatingAddress(final GroupAddress ga)
  	{
  		if (getMainAddress().equals(ga))
  			throw new KNXIllegalArgumentException(
  					"updating address " + ga + " equals main address of this datapoint '" + getName() + "'");
  		if (!invalidating.contains(ga))
  			invalidating.add(ga);
  	}
docs: Adds an invalidating group address to this datapoint to indicate that KNX messages with that address are allowed
  to invalidate the associated datapoint state (i.e., the state value related to this datapoint). An address is
  added at most once.
  
  @param ga the KNX group address to add