A componentbased approach to online software evolution:

SUMMARY Many software systems need to provide services continuously and uninterruptedly. Meanwhile, these software systems need to keep evolving continuously to fix bugs, add functions, improve algorithms, adapt to new running environments and platforms, or prevent potential problems. This situation makes online evolution an important issue in the field of software maintenance and evolution. This paper proposes a component-based approach to online software evolution. Nowadays component technology has been widely adopted. Component technology facilitates software evolution, but also introduces some new issues. In our approach, an application server is used to evolve the application, without special support from the compiler or operating system. The implementation and performance analysis of our approach are also covered

A Modular Approach Enforcing Safe Reconfiguration of Producer-Consumer Applications

Unanticipated software adaptations are becoming increasingly important in the domain of distributed systems. Due to performance and availability requirements, these adaptations need to be enforced at run-time. However for dynamic changes to yield valid systems, a safe state for reconfiguration of the involved software modules must be enforced. This paper proposes a solution to modularize support for achieving safe reconfiguration and separate it from basic application functionality. In addition, we describe a mechanism to obtain a safe state for unanticipated reconfiguration of producer/consumer based systems, rather than being limited to updates of independent software components. The presented method imposes such a safe state with minimal interference to the rest of the system, and with minimal contribution from the programmer. We believe that a wide range of producer/consumer based systems can take advantage of the presented solution. 1