Applying Patterns to Develop Extensible ORB Middleware

Distributed object computing forms the basis for nextgeneration application middleware. At the heart of distributed object computing are Object Request Brokers (ORBs), which automate many tedious and error-prone distributed programming tasks. Like many other distributed applications, conventional ORBs use statically configured software designs, which are hard to maintain, port, and optimize. Likewise, conventional ORBs cannot be extended without modifying their source code, which forces recompilation, relinking, and restarting running ORBs and their associated application objects. This article makes two contributions to the study of extensible and maintainable ORB middleware. First, it presents a case study of key patterns needed to develop ORBs that can be dynamically configured and evolved for specific application requirements and system characteristics. Second, we quantify the impact of applying patterns to reduce the complexity and improve the maintainability of common ORB tasks, such as connection management, data transfer, demultiplexing, and concurrency control.