Personal assistance by means of mobile objects

In the rst part the common structure of a mobile distributed system will be elaborated. A layered model will be presented, including the layers of hardware, operating system kernel, operating system services, middleware and applications. Many structuring concepts are used within these layers, especially with respect to object orientation. They will be shown. Additionally replication and consistency of replicas play an important role within mobile distributed systems. They are integrated too. The second part focuses on operating system and application support for mobile systems. Some research and development results in the areas of PDA operating systems and their applications will be presented. The overall objectives in this paper are: (1) the introduction into the elds of objects, mobility, and replication, (2) the presentation of recent research trends in operating systems usable for mobile distributed (object oriented) systems, and (3) the application of mobile objects in the area of personal assistance. In mobile distributed systems resources of any kind are more and more mobile, applications require mobility, and applications require replication for reasons of eeciency, fault tolerance, and disconnection. The principle of mobility states, that information access and processing should be possible always and everywhere. The market especially for personal assistance evolves into a mass market. A common global model of a mobile distributed system consists of the following ve layers, listed from bottom to top: (1) Hardware, (2) Operating system kernel, (3) System services, (4) Application services, and (5) Applications (see gure 1). Objects, object mobility, and object replication could be found everywhere in the system's global model. Outline of the paper: (1) Motivation and introduction, (2) General model and its layers, (3) Recent trends in mobile distributed operating systems, (4) Personal assistance at the application layer, (5) Summary and conclusions.