The returned meta-information in the entity-header is not the definitive set as available in the original server. It comes from a local or a third-party copy. The set presented MAY be a subset or superset of the original version. For example, including local annotation information about the resource might result in a superset of the meta-information known by the origin server. The use of this response code is not required. It is only appropriate for a response of 200 (OK).