I think that one of the requirements that has not been satisfied by the
current model is the ability to handle legacy web service - although having
reviewed the recent list of requirements sent around by Steve (based on the
use cases), this appears to have been left out (possibly because it is non
functional).

What I would like to see is the 'abstract' choreographies focusing on the
passive monitoring of interactions between multiple participants, and
therefore not imposing any requirements on any of those participants - and
thus coping with legacy web services. This also means that it should have no
'state/variables' that it is required to manage (locally or as part of the
interaction).

Then the 'portable' choreography could aim to support the more active
monitoring of a choreography, but only where all participants support the
choreography interface. Not sure why the 'concrete' choreography is
required, unless the choreography mechanism now will assume the role of
connecting participants?
(G.Brown)