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,,, and 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.