18.104.22.168 If an otherwise valid HTTP PUT request is received that contains properties the server chooses not to persist, e.g. unknown content, LDP servers must respond with an appropriate 4xx range status code [RFC7231]. LDP servers should provide a corresponding response body containing information about which properties could not be persisted. The format of the 4xx response body is not constrained by LDP. LDP servers expose these application-specific constraints as described in section 4.2.1 General.