This file contains associations between messages and objects, as parsed from MDATAx.DAT. This is just what I found from some small samples, and seems to be rather intrinsic to VPA.
+0 n DWORDs For each message from MDATAx.DAT:
Bits 0..10 Object Id (0..2047)
Bits 11..14 Object Type:
0000 if not associated with anything
0001 if message is associated with a planet
0010 if associated with a ship
0011 if associated with a minefield
0100 if associated with an ion storm
0101 if associated with a marker (object
Id is number of marker in VPAx.DB,
"MARK" block, counting from 1
0110 if associated with a wormhole
0111 if associated with an Ufo
Bits 16..? associated VCR number or 0 (?)
E.g., a `(-d0167)' message has the value 08A7h here,
where A7h = 167 is the planet/starbase Id, and bit 11
is set to tell this message belongs to a planet.
+? n WORDs For each message in the VPA database, "IMSG" block
(messages that will be kept): position of this message
in MDATAx.DAT, 1-based.
