DAT is a physical audio format developed by Sony, originally intended as a replacement for the Compact Cassette, but it was strangled by the american music industry before it could release.
Without the failure of DAT, the MiniDisc probably wouldn’t exist.
Also, I don’t yet know how similar DAT is to Digital Compact Cassette.
After looking into it (barely), I found that DAT effectively uses a shrunken-down VHS mechanism. DCC uses a modified Compact Cassette mechanism. There are other differences I don’t fully understand yet.