I put up a preliminary Wiki page highlighting areas where the Proposed OASIS UIMA Specification currently deviates from what we've implemented.
http://cwiki.apache.org/UIMA/architecturecomplianceissues.html These aren't necesarily things we need to address any time soon, since the OASIS UIMA Specification is far from finalized and may evolve. However, it is important that as we do evolve the Apache UIMA implementation we are all informed by the current thinking of the OASIS TC. -Adam