We have found a number of places that use offset-binary numeric representation. This is also called excess-K, or biased, but I think offset binary is a better description of it. In this representation you take an unsigned binary, and just subtract an offset. E.g., for a 3-bit number, mostSignificantBitFirst: bits unsigned twos-comp offsetBinary 000 0 0 -4 001 1 1 -3 010 2 2 -2 011 3 3 -1 100 4 -4 0 101 5 -3 1 110 6 -2 2 111 7 -1 3 At the moment, users have to work around this in Daffodil using inputValueCalc and outputValueCalc. This is feasible, but really awkward for such a simple concept. So we suggest that the next revision of DFDL include dfdl:binaryNumberRep="offsetBinary" Thoughts? ...mikeb Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy <http://www.ogf.org/About/abt_policies.php>