Integration of CORBA services with a dynamic real-time architecture

The Common Object Request Broker Architecture (CORBA) is the most successful representative for an object-bused distributed computing architecture. Although CORBA simplifies the implementation of complex, distributed systems significantly, support of techniques for reliable, fault-tolerant software, such as online-replacement or replication is not within scope of today's CORBA or Real-time CORBA. The Simplex architecture developed at the Software Engineering Institute at Carnegie Mellon University support rs the online-replacement of software components within a fault-tolerant, real-time control application. Simplex middleware consist of both a hard real-time publisher/subscriber service and a soft real-time service to support human-in-the-loop supervisor control activities. We have replaced Simplex' soft real-time services with CORBA services while retaining its hard real-time publication and subscription service. This composite approach allows us to take advantage of both the strength of CORBA in distributed computing and Simplex' strength in hard real-time control applications. In this paper, we will discuss the trade-off issues in this composite system approach and present the tele-laboratory experiment, which is based on the extended Simplex system.