The document looks good. I have a few questions/comments:
1. The document seems mostly about functionality. Will there be a design document as well?
2. Will there be any metastore api changes/additions? If so, it would be good to specify them here also.
3. It would be good to specify in the doc what's in line with SQL standard, which deviates from that.
4. For using a UDF on data from a different database, it seems to me that Hive should prevent from this, at least as a functional goal. Otherwise, all UDFs will be global, and db name becomes namespace, similar to java package name.
5. There seems a little inconsistency between the text and the syntax, thought a very minor point:
Sets of JARs can be saved to the warehouse using CREATE JARSET.
CREATE JARSET | FILESET | ARCHIVESET ...
6. Does "SHOW JARSET | FILESET | ARCHIVESET" need to specify database name?