The chance for ada to support distribution and real-time in embedded systems

Abstract

This paper presents a modification of GLADE —the current GNAT implementation of the Ada 95 Distributed Systems Annex (DSA)— to support the development of distributed applications with hard real-time requirements. This modified implementation, that we call RT-GLADE (Real-Time GLADE), is specially suitable for embedded applications composed of a small number of heterogeneous processors and communication networks, because it ensures predictable timing behaviour. A real-time model of the implementation allows the application developer to determine and optimize the overall timing behaviour by applying the corresponding schedulability analysis and priority assignment techniques. This realtime version of GLADE continues to conform to the DSA, so the entire real-time application can be built within the Ada 95 context. To implement RT-GLADE, we provide a priority-based communication network over standard Ethernet that is used to ensure predictable transmission times.