Acknowledgments I

Advances in software engineering technology continue to assist engineers in building more complex systems than before, but even if these systems are more complex they sustain the same problems of previous developments. First, they are never error-free and second, they need continuous improvement to meet users requests for more and improved functionality. These changes often result in downtime, where users can not use the system. In other types of systems downtime can be interdicted, for instance the switching systems in the telecommunications domain. A dynamic reconfigurable system that updates or replaces software without stopping the executing applications is needed. This thesis discusses support for the modeling and implementation of software systems with a dynamic architecture. Using software architectures as a basis for reasoning about run-time modification makes it possible to use a different approach, dynamic reconfiguration at the architectural level. Introducing architectural agents allows for developers to specify reactiveness in architectural specifications. The introduction of the architectural agent, adds a new dimension to traditional architectural specifications. Agents allow designers to express run-time evolution which is initiated and governed internally in the executing application. The methodology for architectural agents is simple yet capable of describing systems with complex dynamic behavior.