[DFDL-WG] Action 233 (deferred) - "byte order not sufficient..." - draft document on experience with binary format MIL-STD-2045

[Mike Beckerle]

I have created an experience document about the "bit order" issue, which
was a deferred action 233, and the subject of a public comment.

The document is here: http://redmine.ogf.org/dmsf_files/13268. The public
comment item is http://redmine.ogf.org/boards/15/topics/43.

It recommends a new dfdl:bitOrder property, and a new dfdl:byteOrder enum
value, without which it is impossible to model these data formats. It also
recommends  several other improvements to DFDL to facilitate handling these
data formats.

The formats in question are a variety of MIL-STD formats which are all
densely packed binary data. These formats are in broad use. MIL-STD-2045 is
one part of this family and this particular format specification is
generally available without any restrictions from a US DoD web site (
http://assistdocs.com) so I made this specific format the subject of the
document as it illustrates all the problematic issues.

We have implemented the dfdl:bitOrder property in Daffodil, and it works
with some useful tests now passing.

We have also enhanced our TDML implementation to enable creation of tests
for this feature (and in the process actually found two bugs in the
MIL-STD-2045 spec!).

Both the property and this TDML enhancement are described in the document.

The sponsors of the Daffodil project are extremely keen to get this needed
binary support into the DFDL v1.0 standard so as to have multiple DFDL
implementations support it.

...mikeb

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
www.tresys.com
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