The Reference Model of Open Distributed Processing (RM-ODP) is a joint standardization effort by ITU-T and ISO/IEC for the specification of large open distributed systems. RM-ODP is becoming increasingly relevant now because the size and complexity of large distributed systems is challenging current software engineering methods and tools, and because international standards have become key to achieve the required interoperability between the different parties and organizations involved in the design and development of complex systems. RM-ODP defines five viewpoints for decomposing the design activity into separate areas of concern. One of the RM-ODP viewpoints, the computational viewpoint, focuses on the basic functionality of the system and its environment, independently of its distribution. Although several notations have been proposed to model the ODP computational viewpoint, either they are not expressive enough to faithfully represent all its concepts, or they tend to suffer from...