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

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A. Polze
K. Wallnau
D. Plakosh
M. Malek


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 Symplex system's coordinated inverted pendulum demo developed at the SEI, CMU, and a real-time manufacturing system developed at NIST (National Intitute 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.

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