The Expert documentation contains unresolved docbook tags <kw>...</kw> in many places.
The new "calendars" rule attribute isn't mentioned. There's no indication that "duration" is now deprecated (as written in http://blog.athico.com/2010/07/drools-51-m2-release-notes.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+DroolsRSS+(Drools+-+RSS)
Nothing is said about "Live queries". And the javadoc for openLiveQuery describes neither its function, nor parameters or return type.
Javadoc's main page (the top-level index.html) compes up with