I have previously made use of ECJ 15 to evolve behavior from within the Xholon open-source modeling tool. I tried it with ECJ 16, and it works with just a few small changes. In these models, Xholon and ECJ nodes coexist within the same Java tree structure. I have to change the declaration of the ECJ GPTree and GPNode classes, so that they implement IXholon and extend Activity, and then add a few new methods. Thanks to Sean and the rest of the ECJ team, Ken -- Ken Webb Primordion www.primordion.com/Xholon Ottawa, Ontario, Canada Xholon and Cellontro open-source projects.