Nu: a dynamic aspect-oriented intermediate language model and virtual machine for flexible runtime adaptation

• Authors: Robert Dyer;Hridesh Rajan
• Venue: Proceedings of the 7th international conference on Aspect-oriented software development
• Year: 2008

A variety of dynamic aspect-oriented language constructs are proposed in recent literature with corresponding, compelling use cases. Such constructs demonstrate the need to dynamically adapt the set of join points intercepted at a fine-grained level. The notion of morphing aspects and continuous weaving is motivated by this need. We propose an intermediate language model called Nu, that extends object-oriented intermediate language models with two fine-grained deployment primitives: bind and remove. These primitives offer a higher level of abstraction as a compilation target for dynamic aspect-oriented language constructs, thereby making it easier to support such constructs. We present the design and implementation of the Nu model in the Sun Hotspot VM, an industrial strength virtual machine, which serves to show the feasibility of the intermediate language design. Our implementation uses dedicated caching mechanisms to significantly reduce the amortized costs of join point dispatch. Our evaluation shows that the cost of supporting a dynamic deployment model can be reduced to as little as ~1.5%. We demonstrate the potential utility of the intermediate language design by expressing a variety of aspect-oriented source language constructs of dynamic flavor such as CaeserJ's deploy, history-based pointcuts, and control flow constructs in terms of the Nu model.