R Component Calculus Component Calculus

the governments of the People's Republic of China and Portugal through a contribution to the UNU Endownment Fund. As well as providing two-thirds of the endownment fund, the Macau authorities also supply UNU/IIST with its ooce premises and furniture and subsidise fellow accommodation. The mission of UNU/IIST is to assist developing countries in the application and development of software technology. UNU/IIST contributes through its programmatic activities: 1. Advanced development projects, in which software techniques supported by tools are applied, 2. Research projects, in which new techniques for software development are investigated, 3. Curriculum development projects, in which courses of software technology for universities in developing countries are developed, 4. University development projects, which complement the curriculum development projects by aiming to strengthen all aspects of computer science teaching in universities in developing countries, 5. Schools and Courses, which typically teach advanced software development techniques, 6. Events, in which conferences and workshops are organised or supported by UNU/IIST, and 7. Dissemination, in which UNU/IIST regularly distributes to developing countries information on international progress of software technology. Fellows, who are young scientists and engineers from developing countries, are invited to actively participate in all these projects. By doing the projects they are trained. At present, the technical focus of UNU/IIST is on formal methods for software development. UNU/IIST is an internationally recognised center in the area of formal methods. However, no software technique is universally applicable. We are prepared to choose complementary techniques for our projects, if necessary. UNU/IIST produces a report series. Reports are either Research R , Technical T , Compendia C or Administrative A. They are records of UNU/IIST activities and research and development achievements. Many of the reports are also published in conference proceedings and journals. Abstract This report introduces a component calculus, whereby a system can be divided into a number of interconnected components. We model the behaviour of individual service by a design, which enables one to separate the responsibility of clients from the commitment made by the system. We adopt the notion of reenement to formalise the replaceability of components. This allows developers to improve the system performance by reorganising its data components. He Jifeng is a senior research-fellow of UNU/IIST. He is also a professor of computer science at the Software Engineering Institute of East China Normal University. His research interests include the theories of programming languages, formal methods for safety-critical systems, parallel and …