The vision of pervasive computing promises a shiſt from information technology per se to what can be accomplished by using it, thereby fundamentally changing the relationship between people and information technology. In order to realize this vision, a large number of issues concerning user experience, contextual change, and technical requirements should be addressed. We provide a design rationale for pervasive computing that encompasses these issues, in which we argue that a prominent aspect of user experience is to provide user control, primarily founded in human values. As one of the more significant aspects of the user experience, we provide an extended discussion about privacy. With contextual change, we address the fundamental change in previously established relationships between the practices of individuals, social institutions, and physical environments that pervasive computing entails. Finally, issues of technical requirements refer to technology neutrality

This dissertation provides constructive proof, through the implementation of a middleware, that distribution transparency is practical, generic, and extensible. Fault tolerant distributed services can be developed by using the failure detection abilities of the middleware. By generic we mean that the middleware can be used for many different programming languages and paradigms. Distribution for each kind of language entity is done in terms of consistency protocols, which guarantee that the semantics of the entities are preserved in a distributed setting. The middleware allows new consistency protocols to be added easily. The efficiency of the middleware and the ease of integration are shown by coupling the middleware to a programming system, which encompasses the object oriented, the functional, and the concurrent-declarative programming paradigms. Our measurements show that the distribution middleware is competitive with the most popular distributed

We propose a design for CORBA's Transaction Service with soft real-time and high availability properties. Soft real-time is ensured by reducing the variability of reply latencies. High availability is ensured by quick restarts and fault tolerance. We reduce the time for a restart by periodic checkpointing, and implement fault tolerance by object replication. Replication is implemented on top of Eddie, a freeware request router developed by OTP. Finally, we discuss how to map subsystems to processing nodes to improve efficiency and availability. CONTENTS 1 Contents 1 Introduction 2 1.1 real-time system and high availability . . . . . . . . . . . . . . . 2 1.2 Transactional Algorithms . . . . . . . . . . . . . . . . . . . . . . 2 1.2.1 Flat or Nested Transactions . . . . . . . . . . . . . . . . . 4 1.3 CORBA Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3.1 Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3.2 CORBA Architecture . . . . . . . . . ...

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