I ran across another community working in the same space as DFDL: BSDL as part of MPEG21 (someone at the NARA conference mentioned it). From a quick look at what they have, it appears to be inverse DFDL with plans to make DFDL next, i.e. they go from model to output binary format, but not vice versa. Similar schema approach, etc. with some comments on things in schema that they don't allow. I haven't found a spec doc yet, just a paper and some presentations you can google for. Jim Bitstream Syntax Description Language: Application of XML-Schema ... <http://www2002.org/CDROM/alternate/334/> ... Language (BSDL) that embraces such XML bitstream descriptions. ... 2/; [13] IEEE Standard for Binary Floating-Point ... Final Draft Amendment 4: Streaming video profile ... www2002.org/CDROM/alternate/334/