Both the implementation and the user’s view of eXene rely heavily on the concurrency model provided by CML . CML is based on the sequential language SML[MTH90, MT91] and inherits the following good features of SML: functions as first-class values, strong static typing, polymorphism, datatypes and pattern matching, lexical scoping, exception handling and a state-of-the-art module facility. The sequential performance of CML benefits from the quality of the SML/NJ compiler. In addition CML has the following properties: