Towards Realisation of Evolvable Runtime Variability in Internet-Based Service Systems via Dynamical Software Update

Abstract

Today's Internet-based service systems tend to run in open environments and try to satisfy varying requirements. In the context, the changes of requirements and environments can emerge at any point of their life cycle, and their runtime variability is supposed to be evolvable to deal with the changes. In other words, the number, type or attribute of variability elements (variation points and their associated variants) in the systems is regarded to be changeable, especially at runtime. How to realise evolvable runtime variability in software systems is a challenge in the community of software engineering. Software architecture is supposed to support updating software without interrupting service if runtime variability is to be changed. Besides, the relevant mechanisms have to be provided to achieve dynamic update. Thus, we propose a dynamically reconfigurable reference architecture to construct the systems with evolvable software variability. The resultant system established using our approach consists of variability units and their containers. Variability units embody the variability elements that can be changed through local relay, i.e., starting a new version of variability unit to take place of older ones. Containers are mainly used to carry out the dynamic updating for variability units and realise the functionality invocation among different variability units. They can also be added, removed or replaced without shutting down the entire system. We analyse the requirements and scenarios of evolvable runtime variability in the case of Personal Data Resource Network, and further show the effectiveness and applicability of our approach by constructing the system using our class library and solving the issues proposed in the case.