Fine-grained semi-automated runtime evolution

Modern software systems that play critical roles in society are often required to change at runtime so that they can continuously provide essential services in the dynamic environments they operate in. Updating open, distributed software systems at runtime is very challenging. Using runtime models as an interface for updating software at runtime can help developers manage the complexity of updating software while it is executing. In this chapter we describe an approach to updating Java software at runtime through the use of runtime models consisting of UML class and sequence diagrams. Changes to models are transformed to changes on Java source code, which is then propagated to the runtime system using the JavAdaptor technology. In particular, the presented approach permits in-the-small software changes, i.e., changes at the code statement level, as opposed to in-the-large changes, i.e., changes at the component level. We present a case study that demonstrates the major aspects of the approach and its use. We also give the results of a preliminary evaluation of the approach.