A revised, inheritance-supporting parallel object model in PDEFA-I

Abstract

PDEFA is a distributed Ada95 pre-compiler, compiler and run-time system. PDEFA-I is the latest version of PDEFA that supports inheritance between parallel objects. Because of the inheritance anomaly problem with concurrent objects Ada95 does not support this mechanism, so we have to slightly modify the language to make inheritance possible. The code of each interface of a protected object in Ada95 is divided into two parts, synchronization code called condition and implementation code called action. These two parts of code can be changed or replaced independently in subclasses, making great effort for maximum code reuse. Consequently, PDEFA evolves into PDEFA-I with its parallel object model improved in order to solve the inheritance anomaly. We demonstrate mainly the work we have done with service objects.