x1=das1 is a signal recording and playback tape-type medium (cassette/DAT/tape drive) containing data/sound/image x2=dat1 with data storage mechanism/method x3 (analog/digital)
x1=d1=v4 is a signal recording and playback tape-type medium (cassette/DAT/tape drive) containing data/sound/image x2=v2 with data storage mechanism/method x3 (analog/digital)