Data Language (DL) was originally conceived of as the next evolutionary step in computer graphics file formats for describing 3D geometry and associated scene data, but its applicability is potentially much broader. (Update: Its utility has since been supplanted by Google's protobuf and flatbuffers, but it still contains novel and potentially fruitful ideas.)

A document describing DL can be found here. Two implementations currently exist. The first is a 'reference' implementation in Standard ML to help confirm that the design is logically sound, and to provide a starting point for future utilities. It is available here. The second is written in C++ and is implemented to optimize data structures typically used by 3D graphics applications.