Structured History Data provides metadata describing an entry in the history database. The Server shall define what uniqueness means for each Structured History Data structure type. For example, a Server may only allow one Annotation per timestamp which means the timestamp is the unique key for the structure. Another Server may allow Annotations to exist per user, so a combination of a username and timestamp may be used as the unique key for the structure. In 6.8.3.3, 6.8.3.4, 6.8.3.5, and 6.8.3.6 the terms ‘Structured History Data exists’ and ‘at the specified parameters’ means a matching entry has been found at the specified timestamp using the Server’s criteria for uniqueness.

In the case where the Client wishes to replace a parameter that is part of the uniqueness criteria, then the resulting StatusCode would be Bad_NoEntryExists. The Client shall remove the existing structure and then Insert the new structure.