There is a symantic change event, that notifies a client if somethign changed that a client should be aware of, such as an engineerng unit. There should also be a Historical Configuration Change Event. This event would be generate when either a historical nodes historical configuration is changed (added/deleted assigned to a different configuration). This event would allow a client to easily discover if an items historical configuration has changed.

There are Audit events available for historical value changes, entering of Annotation and other changes. A client may also want to be able to obtain this same information in a more general manner. I.e. an event that disclose that either a historical value has been edited or an annotation has been entered for the historicalnode.