Reflections and Aspects
Shigeru Chiba (Tokyo Institute of Technology) focused his tutorial on mainstream transformation usages such with the use of reflection and aspects.
Reflection can be seen as dynamic transformation allowing the application to change its behavior during runtime by intercepting calls and potentially augmenting the data structures. He has written several reflective systems including and more recently openC++, openJava, and Javassist (part of the JBOSS project). He conceded that reflection was hard to use and explained how Aspect-Oriented Programming (AOP) is a safer way to change behaviors. AOP let an advice be introduced around a point cut. The advice can include code to be called before and after and new storage needs. The point cut identifies the parts of the code that will be affected by the advice. Shigeru then came back to the difficulties of using reflection and proposed the use of dynamic aspects to resolve these where new aspects can be brought in during execution. This is particularly interesting for systems that can have no downtime. He mentioned the current effort by many to separate the definition of the advice from the point cut, a concept that he has built into GluonJ, his latest system. Finally, he dismissed criticisms on the limited scope of AOP by pointing out that he preferred to push a working solution forwards than to refine a non-working one!