From UC2 source code (SUPERMAN.H)

Total (multivolume) archive format:
   XHEAD [BAREBLOCKS...] CDIR [SEAL] [CRYPT] [BANNER]

File format (single volume):
   FHEAD 'part of archive' [DAMAGE_RECOVERY_INFO]

BAREBLOCK ::=
   none     // directory
   'data'   // file
   'data'   // master

CDIR ::=
   COMPRESS '[BASINF...]'

BASINF ::=
   OHEAD - OSMETA DIRMETA
         - OSMETA FILEMETA COMPRESS LOCATION
         - MASMETA COMPRESS
         - end of list

SEAL ::=
   ... // documented in USAFE/USEAL software

CRYPT ::=
   ... // documented in UCRYPT software

The order of the BASINF objects is NOT random. There are many possible orders
but some things have to be correct:

 - first the directory then its contents
 - revisions in reverse order (first n then n-1 until 0) only !!
 - no missing revisions (always 5,4,3,2,1 etc never 5,2,1)
   (notice we are talking EXTERNAL revision numbers here)

But notice:

 - masters, directories and files can bee freely intermixed
 - neuro models can be put both before and after usage
 - the order in the archive does not have to resemble the order in the CDIR