Currently the Hive Language Manual and many other critical pieces of documentation are on the Hive wiki.
Right now we count on the author of a patch to follow up and add wiki entries. While we do a decent job with this, new features can be missed. Or using running older/newer branches can not locate relevant documentation for their branch.
..example of a perception I do not think we want to give off...
We should generate our documentation in the way hadoop & hbase does, inline using forest. I would like to take the lead on this, but we need a lot of consensus on doing this properly.