abc abc: Workbench for Aspect-Oriented Programming Language and Compiler Research

Presenters: Laurie Hendren and Oege de Moor

abc Web Site: (http://aspectbench.org)


What is Aspect-Oriented Programming and why is it important?

Aspect-oriented programming offers a new set of language features to improve modularity. These features fall into two categories: open classes (to inject new members into existing classes) and advice (transforming computations by intercepting events). Conceptually, one can think of a piece of advice as observing the execution of a base program: when certain patterns of events occur, that triggers the execution of some extra code in the advice. The most popular implementation of these ideas is an extension of Java called AspectJ. Apart from AspectJ, there is a rapidly growing number of aspect-oriented languages emerging from the research community, including Alpha, Aspect#, Demeter/J, JAsCo, Loom.NET, and many others. Indeed, the paradigm of aspect-orientation poses several interesting challenges for programming language researchers, ranging from questions of semantics, through language design, to optimisations and safety analyses.

Perhaps the most obvious of these challenges is one of efficiency: conceptually, the paradigm of `observing a base program' is appealing, but when implemented naively, it would result in unacceptable overheads. A compiler must therefore shift as much of the event matching process from runtime to compiletime. Some features of AspectJ do however require runtime checks, and for those the challenge is to quantify the overheads, and reduce them where possible.

Another open problem is how we can control the effects of aspects, without limiting their expressive power too much. To what extent can an aspect observe the implementation details of the base program? If it can observe implementation details that are otherwise hidden, can we prevent the extra code from breaking invariants in the base program?

What is the purpose of this tutorial?

The purpose of this tutorial is to introduce the paradigm of aspect-orientation, and the challenges that it presents, from the point of view of programming language and compiler researchers. It will then present the AspectBench Compiler (abc for short), which is a full implementation of the AspectJ language. It has been designed to allow easy experimentation with new language features, new analyses and new optimisations.

The frontend of abc is built with Polyglot, an extensible Java frontend built by Andrew Myers and his students at Cornell. The backend of abc uses Soot, the Java analysis and optimisation framework developed by Laurie Hendren and her students at McGill. The tutorial is thus of independent interest as a study in the use of both Polyglot and Soot. The abc project is a joint project between the Programming Tools Group at Oxford, the Sable Research Group at McGill, and BRICS at the University of Aarhus.

What you will learn in this tutorial?


Presenter Biography Information
Laurie Professor Laurie Hendren, McGill University

Laurie Hendren received the B.Sc.(Honours) and M.Sc degrees in Computing and Information Science at Queen's University, Kingston, Canada. She received the Ph.D. degree from Cornell University, Ithaca, N.Y. Her Ph.D. thesis was in the area of automatic parallelization of programs with recursive pointer data structures.

Since 1990 she has been a faculty member in the School of Computer Science at McGill University where she has led the McCAT optimizing/parallelizing compiler project, and currently leads the Sable project that concentrates on compiling and optimizing Java. During the 2003-2004 academic year she visited Professor de Moor at Oxford University, where they started the joint abc project, the topic of this tutorial.
Oege Professor Oege de Moor, Oxford University

Oege de Moor received an M.Sc. degree from the University of Utrecht, the Netherlands. He did his doctoral (D.Phil.) work at Oxford, on a characterisation in category theory of algorithmic paradigms such as dynamic programming. He has held visiting appointments at the University of Tokyo, Chalmers University and Microsoft Research (both Redmond and Cambridge).

Since 1994 he has been a faculty member at Oxford, where he founded the Algebra of Programming research group, jointly with Richard Bird. After the publication of a textbook on that subject in 1997, he turned to the general area of meta-programming, and founded the Programming Tools Group. Research topics in the group include type systems for metaprogramming, mechanised support for refactoring, and aspect-orientation.