i have read Cesare Pautasso's presentation about RESTful service composition with JOpera .
Does the example workflow (doodle map mashup, p27) integrate existing REST apis ? If yes, is this testable in the current release (2.4.2) ? I have only found the screenshot of the doodle REST api call  in the documentation.
As I am currently dealing with REST service integration in workflows I find your project really interesting and look forward to your answer.