DS = DAZ Studio, probably in this case DS3 or earlier, or 4.0 or earlier, or it may be DS settings for the V4/M4 etc. version of soemthign like hair that has old and Genesis versions.
TRX=TriAx, Genesis and other weight-mapped figures for DS4+, or it may be a 4.5+ version
DPC=Poser content
Unfortunately that doesn’t absolutely pin down which are optional - if it isn’t a dual thing I would expect the TRX to be self-contained, butt hat can’t be relied on when there’s an item with Poser and DS versions of the same thing.