A file format that embeds a binary heiarchial serializer within a normal change set. Initially built to support DeltaStreams, but should be generic enough for any code storage format that desires maximal backward-compatability with older squeak versions. It has three nice features:the file can be filed in as a normal change-set if no reader is loadedthe format can be written in append-only mode, (like the .changes file)The serialization format is binary, pointer-based and fast, as it requires no parsing or compiling.