Real-Time Computing with Off-the-Shelf Components: The Case for CORBA

The Common Object Request Broker Architecture (CORBA) is a successful standardized system integration framework based on distributed object technology. The key feature of CORBA is that users can create application systems by integrating existing heterogeneous hardware and software components. CORBA abstracts from implementation details like object's locations, hardware and operating systems.Correctness of real-time computing depends not only on output values generated by a computation but also on the times at which outputs are generated. Therefore, locations, hardware speeds, workloads, and the schedulers used by the operating systems can affect timing and the correctness of real-time computing.The real-time extension of CORBA is not a simple refinement of the existing CORBA model. Rather, it is at the heart of CORBA specifications: what should and should not be abstracted away and how to do it. In this paper, we study the application of principles from the real-time computing domain within a CORBA-based framework. We have investigated the Simplex system's coordinated inverted pendulum demo developed at the SEI, CMU, and a real-time manufacturing system developed at NIST (National Institute of Standards and Technology). We view those applications as model problems that are present in numerous application domains (telecom, manufacturing, etc.).Based on our experiences, we have developed Composite Objects as a methodology for predictable integration of real-time and distributed (non-real-time) computing. We discuss our implementation of Composite Objects and present results of an experimental evaluation.

[1]  K. H. Kim,et al.  An implementation model for time-triggered message-triggered object support mechanisms in CORBA-compliant COTS platforms , 1998, Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98).

[2]  Bhavani M. Thuraisingham,et al.  Concurrency control in real-time object-oriented systems: the affected set priority ceiling protocols , 1998, Proceedings First International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC '98).

[3]  Douglas C. Schmidt,et al.  A high-performance end system architecture for real-time CORBA , 1997, IEEE Commun. Mag..

[4]  Lui Sha,et al.  Evolving dependable real-time systems , 1996, 1996 IEEE Aerospace Applications Conference. Proceedings.

[5]  Richard Mark Soley,et al.  Object management architecture guide (3rd ed.) , 1995 .

[6]  Shirish S. Sathaye,et al.  Generalized rate-monotonic scheduling theory: a framework for developing real-time systems , 1994, Proc. IEEE.

[7]  K. H. Kim,et al.  Toward new-generation real-time object-oriented computing , 1995, Proceedings of the Fifth IEEE Computer Society Workshop on Future Trends of Distributed Computing Systems.

[8]  Lui Sha,et al.  The real-time publisher/subscriber inter-process communication model for distributed real-time systems: design and implementation , 1995, Proceedings Real-Time Technology and Applications Symposium.

[9]  Gerhard Fohler,et al.  Predictable network computing , 1997, Proceedings of 17th International Conference on Distributed Computing Systems.

[10]  Lui Sha,et al.  Composite objects: real-time programming with CORBA , 1998, Proceedings. 24th EUROMICRO Conference (Cat. No.98EX204).

[11]  Bhavani M. Thuraisingham,et al.  On real-time extensions to object request brokers: a panel position paper , 1996, Proceedings of WORDS'96. The Second Workshop on Object-Oriented Real-Time Dependable Systems.