| Ever since distributed systems technology became increasingly popular in the real-time computing area about two decades ago, real-time distributed object computing technologies have been attracting more attention from researchers and engineers. While highly effective object-oriented methodologies are now widely adopted to reduce the development complexity and maintenance costs of large scale non-real-time software applications, real-time systems engineering practice has not kept pace with these system development methodologies. Indeed, real-time design techniques have not fully adopted the concepts of modular design and analysis which are the main virtues of object-oriented design technologies. As a consequence, the demand for object-oriented analysis, design, and implementation of large-scale real-time applications has been growing.; To address the need for object-oriented real-time systems engineering environments we propose the Real-Time DEVS/CORBA (RTDEVS/CORBA) distributed object computing environment. In this dissertation, we show how this environment is an extension of previously developed DEVS-based modeling and simulation frameworks that have been shown to support an effective modeling and simulation methodology in various application areas. The major objective in developing Distributed Real-Time DEVS/CORBA is to establish a framework in which distributed real-time systems can be designed through DEVS-based modeling and simulation studies, and then migrated with minimal additional effort to be executed in the real-time distributed environment. This environment provides generic support for developing models of distributed embedded software systems, evaluating their performance and timing behavior through simulation and easing the transition from the simulation to actual executions. In this dissertation we describe, in some detail, the design and implementation of the RTDEVS/CORBA environment. It was implemented over Visibroker CORBA middleware along with the use of ACE/TAO real-time CORBA services, such as the real-time event service and the runtime scheduling service. Implementation aspects considered include time synchronization issues, priority-based message dispatching for timely message delivery, implementation of activity with threads, and other features required for simulating and executing real-time DEVS models. Finally, application examples are presented in the last part of the dissertation to show applicability of the environment to real systems-engineering problems. |
