| Abstract: | The development of distributed systems is an intricate task due to inherent characteristics of such systems. In this paper these characteristics are categorised into software engineering, concurrency, distribution and non-functional criteria. Popular classes of distributed systems are classified with respect to these challenges, and it is deduced that modern technological trends lead to the inception of new application classes with increased demands regarding challenges from more than one area. One recent example is the class of ubiquitous computing, which assumes dynamic scenarios in which devices come and go at any time. Furthermore, it is analysed to which extent today's prevailing software development paradigms – object, component, service and agent orientation – are conceptually capable of supporting the challenges. This comparison reveals that each of the paradigms has its own strengths and weaknesses and none addresses all of the challenges. The new active component approach is proposed aiming at a conceptual integration of the existing paradigms in order to tackle all challenges in an intuitive and unified way. The structure, behaviour and composition of active components are explained, and an infrastructure for active components is introduced. To underline the usefulness of the approach real-world applications is presented and an evaluation according to the challenges is given. |
