When an alarm is in the address space the values of the properties may hold values that change over time (e.g. the Quality/SourceTimestamp) or properties which can be changed (e.g. AlarmLimits).

The specification is not clear on what to do if these values change. Options are:

1) Change the property values and generate a new event with a new event id;
2) Change the property values but do not generate an event;
3) Do not change the property values unless an event is generated for another reason (e.g. alarm acked).

None are ideal and potentially create issues wrapping existing non-UA alarm systems. 3) seems preferable with caveat that changes to alarm limits shall always trigger an event.