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Javelin is a Java-based infrastructure for parallel Internet computing. This paper presents Javelin 2.0, focusing on the enhancements that distinguish it from prior versions of Javelin 9, 16, 15]. With regard to architecture, the paper presents enhancements that facilitate aggregating larger sets of host processors. The paper then presents: a branch-and-bound computational model, the supporting Javelin 2.0 architecture, a scalable task scheduler using distributed work-stealing, a distributed eager scheduler, implementing fault tolerance, and the results of performance experiments. Taken as a whole, Javelin 2.0 frees application developers from concerns about complex interprocessor communication and fault tolerance among Internetworked hosts. When all or part of their application can be cast as a piecework or a branchand-bound computation, Javelin 2.0 allows developers to focus on the underlying application without sacri cing performance.

Persistent object stores require a way to automatically upgrade persistent objects, to change their code and storage representation. Automatic upgrades are a challenge for such systems. Upgrades must be performed in a way that is efficient both in space and time, and that does not stop application access to the store. In addition, however, the approach must be modular: it must allow programmers to reason locally about the correctness of their upgrades similar to the way they would reason about regular code. This paper provides solutions to both problems.The paper first defines upgrade modularity conditions that any upgrade system must satisfy to support local reasoning about upgrades. The paper then describes a new approach for executing upgrades efficiently while satisfying the upgrade modularity conditions. The approach exploits object encapsulation properties in a novel way. The paper also describes a prototype implementation and shows that our upgrade system imposes only a small overhead on application performance.