(And by that I mean the file hme-protocol.html, as found in TiVo's Java SDK. I refer to the version in 1.4.1 here.) Not only are some things undocumented, but more interestingly, it documents some things that aren't. One is "HME Receiver Compliance", a link to a document that doesn't exist (or at least, isn't in the package). If it did, presumably it would give some additional details for people who wanted to implement HME receivers -- i.e., the Tivo side -- on non-Tivo hardware. I'd love to see that. But the most intriguing is this section: Also in that section: I can't find anything relevant for "Trio Mind" on Google.