This article presents a mathematical characterization of object-oriented concepts by defining an observation-oriented semantics for a relational objectoriented language with a rich variety of features including subtypes, visibility, inheritance, type casting, dynamic binding and polymorphism. The language is expressive enough for the specification of object-oriented designs and programs. We also propose a calculus based on this model to support both structural and behavioral refinement of object-oriented designs. We take the approach of the development of the design calculus based on the standard predicate logic in Hoare and He’s Unifying Theories of Programming (UTP). We also consider object reference in terms of object identity as values and mutually dependent methods.

We present a model for component software. We describe how components are specified at the interface level, design level and how they are composed. From its external view, a component consists a set of interfaces, provided to or required from its environment. From its internal view, a component is an executable code that can be coupled with other components via its interfaces. The developer has to ensure that the specification of a component is met by its design and implementation. We also combine component-based and object-oriented techniques in component-based software development Keywords: Component, Contract, Interface, Object-Orientation, Refinement This report is a refined version of UNU-IIST Report 276 and is to be presented at and published in the proceedings IFIP WCC-TCS2004, 24-26 August 2004, Toulouse, France.

Abstract not found

We give a formal model of component interface for real-time component based systems. We add to the speci cation of a method a time constraint which is a relation between the resource availability and the amount of time spent to perform the method. We de ne contract to include method speci cation, and de ne component as an implementation of a contract. This implementation may require services from other components with some assumption about the schedule for the use of shared methods and resources with the presence of concurrency. Our model supports the separation between functional and non-functional requirements, and the formal compositional veri cation of component-based real-time systems.

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 office 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