JCR2 defines two optional features related to observation.

The first, OPTION_OBSERVATION_SUPPORTED, seems to basically be JCR1 observation with a few relatively minor changes (although one of these assumes that identifiers exist for nodes and properties). Additionally, this feature relaxes the requirements for which events fire when a tree of nodes is moved, copied, or deleted, matching the behavior of our existing observation code.

There is also a new feature defined - OPTION_JOURNALED_OBSERVATION_SUPPORTED. This allows sessions to review recent events in a journaled format. This may be useful for ModeShape in the future, but is not the focus of this issue.