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. Copyright © 2006 John Wiley & Sons, Ltd.

The continuous requirements of evolving a delivered software system and the rising cost of shutting down a running software system are forcing researchers and practitioners to find ways of updating software as it runs. Dynamic update is a kind of software evolution that updates a running program without interruption. This paper covers the fundamental issues of the mechanisms of dynamic update theoretically. Based on a similarity analysis of many typical approaches to dynamic update during the past decades, we propose a unified formal model (namely, Dynamic Update Connector) to specify mechanisms of updating an architectural component, and reason about its properties. The model borrows the concept of connectors from software architecture community and is specified using process algebra CSP. We also demonstrate the applications of our DUC model.

Runtime environment of software are becoming more and more dynamic and changeful, while pervasive computing and Web services further this situation. Software systems are not only becoming larger, more complex, and also more rigid, which make it difficult to evolve software. This paper focuses on online evolution, more exactly, how to make online evolution process convenient and smart, with help of runtime software architecture (RSA). Following issues are discussed in this paper: types of software environment changes, the incarnation of RSA, retrieval and manipulation of RSA, the relation between RSA and the runtime system, and a visual tool to show RSA, and make evolution process more easy and intuitionist.

How to personalize an e-learning system has become an interesting question. The purpose of this paper is to demonstrate an innovative idea of personalizing an e-learning system driven by knowledge flow and show the stratified architecture and the current progress made in Peking University.