From Component Infrastructure To Component - Based Development

Much of the existing work in component-based software technology has concentrated on developing infrastructure capabilities and middleware solutions for connecting independent pieces of system functionality. The result of this work is a range of maturing infrastructure products for supporting deployment of distributed systems. Examples include message-oriented middleware (MOM) products such as Microsoft's MQ Server and IBM's MQSeries, and object request brokers (ORBs) such as Microsoft's Distributed Component Object Model (DCOM) and the various implementations of the Object Management Group's (OMG's) Common Object Request Broker Architecture (CORBA) [3]. The availability of these products has led many application developers to consider their use in the development and deployment of large, distributed, mission-critical applications requiring robust operation in the face of high transaction rates, multiple simultaneous users, and so on. However, to achieve this requires substantially more than the component infrastructure products now available. It requires a move from component infrastructure products to a broader notion of component-based development (CBD). In particular, to be effective, developers of large-scale, mission-critical applications require many additional capabilities, including ways to: • reengineer legacy applications to harvest existing components reusable in other applications, or replaceable by newer technologies; • find suitable components both locally and externally; • integrate components implemented in a variety of different technologies; • validate a component's behavior before using it; • manage multiple implementations of the same component in different technologies, and as it evolves over time. It is our belief that large-scale adoption of component-oriented approaches in these demanding business applications must be built on four key advances: • methods for designing CBD solutions that help the organization focus on the major functional pieces of their domain, and how those pieces will interact; • tools that support specification of business components using techniques that allow the functionality to be described independently of a particular implementation technology; • implementation techniques for components that support demanding requirements for key business goals such as performance, usability, availability, etc.; • a component management and assembly infrastructure to knit together all the pieces specified, built, and acquired, even when those pieces have been developed using different technologies, or by different people. The next two sections of this paper briefly expand on these ideas, and focus on how these advances can be realized in practice. The paper concludes with a brief summary. The move toward CBD requires existing software analysis and design approaches to be reconsidered. In particular, …