Module v4 

Constants

DOCUMENT_VERSIONS_V4

Document serialization moves to format 3: the document is stamped with the data contract version its bytes conform to, right after the format prefix. The stamp lets a property carry requiredSince (required from a given contract version) while documents written before that version keep the presence-flagged layout they were serialized with. Formats 0-2 predate the stamp and deserialize with an unstamped (pre-annotation) layout.