Timothy H. Harrison

The design and performance of a real-time CORBA event service

The CORBA Event Service provides a flexible model for asynchronous communication among objects. However, the standard CORBA Event Service specification lacks important features required by real-time applications. For instance, operational flight programs for fighter aircraft have complex real-time processing requirements. This paper describes the design and performance of an object-oriented, real-time implementation of the GORBA Event Service that is designed to meet these requirements.This paper makes three contributions to the design and performance measurement of object-oriented real-time systems. First, it illustrates how to extend the CORBA Event Service so that it is suitable for real-time systems. These extensions support periodic rate-based event processing and efficient event filtering and correlation. Second, it describes how to develop object-oriented event dispatching and scheduling mechanisms that can provide real-time guarantees. Finally, the paper presents benchmarks that demonstrate the performance tradeoffs of alternative concurrent dispatching mechanisms for real-time Event Services.

A high-performance end system architecture for real-time CORBA

Many application domains (e.g., avionics, telecommunications, and multimedia) require real-time guarantees from the underlying networks, operating systems, and middleware components to achieve their quality of service (QoS) requirements. In addition to providing end-to-end QoS guarantees, applications in these domains must be flexible and reusable. Requirements for flexibility and reusability motivate the use of object-oriented middleware like the Common Object Request Broker Architecture (CORBA). However, the performance of current CORBA implementations is not yet suited for hard real-time systems (e.g., avionics) and constrained latency systems (e.g., teleconferencing). This article describes the architectural features and optimizations required to develop real-time ORB end systems that can deliver end-to-end QoS guarantees to applications. While some operating systems, networks, and protocols now support real-time scheduling, they do not provide integrated solutions. The main thrust of this article is that advances in real-time distributed object computing can be achieved only by systematically pinpointing performance bottlenecks; optimizing the performance of networks, ORB end systems, common services, and applications; and simultaneously integrating techniques and tools that simplify application development.

Operating system support for high-performance, real-time CORBA

A broad range of applications (such as avionics, telecommunication systems, and multimedia on demand) require various types of real-time guarantees from the underlying middleware, operating systems, and networks to achieve their quality of service (QoS). In addition to providing real-time guarantees and end-to-end QoS, the underlying services used by these applications must be reliable, flexible, and reusable. Requirements for reliability, flexibility and reusability motivate the use of object-oriented middleware like the Common Object Request Broker Architecture (CORBA). However the performance of current CORBA implementations is not suitable for latency-sensitive real-time applications, including both hard real-time systems (e.g., avionics), and constrained latency systems (e.g., teleconferencing). This paper describes key changes that must be made to the CORBA specifications, existing CORBA implementations, and the underlying operating system to develop real-time ORBs (RT ORBs). RT ORBs must deliver real-time guarantees and end-to-end QoS to latency-sensitive applications. While many operating systems now support real-time scheduling, they do not provide integrated solutions. The main thesis of this paper is that advances in real-time distributed object computing can be achieved only by simultaneously integrating techniques and tools that simplify application development; optimize application, I/O subsystem, and network performance; and systematically measure performance to pinpoint and alleviate bottlenecks.

Object-oriented framework for high-performance electronic medical imaging

This paper describes the design and performance of an object-oriented communication framework we developed to meet the demands of next-generation distributed electronic medical imaging systems. Our framework combines the flexibility of high-level distributed object computing middleware (like CORBA) with the performance of low-level network programming mechanisms (like sockets). In the paper, we outline the design goals and software architecture of our framework, illustrate the performance of the framework over ATM, and describe how we resolved design challenges we faced when developing an object- oriented communication framework for distributed medical imaging.