Hi,
The doc you linked to seems rather old (SU5) to me (nothing about observers for instance).
BUT the ruby doc has always been (IMHO) crappy, with a lot of errors and voids, not to speak of the examples !
For me it is often a trial-error-trial-error-trial-chance-got it! process
EDIT: sorry, there are some infos about observers... but it seems that there is nothing more than in the 'old' doc, if not less