The historical event replace functionality clear states that a nodeid is required to replace a record. The historical Event Update section implies an EventId is required for replace or that it can uniquely identify and event. this text should be updated to more clearly state an EventId, if it is provided and exist in the historian will result in a replace if it does not exit will result in an insert, if not provided then it is server depended on how it determines if the record is an update or inserts.