Modular Design for the Java Virtual

We provide a modular high-level deenition of the Java Virtual Machine (JVM) architecture. We decompose the machine into three components { the loader, the bytecode veriier and the interpreter { each for a hierarchy of four stepwise reened JVM program layers. These layers naturally correspond to the structuring of Java into sublanguages with imperative, procedural, object-oriented and exception handling features. We give our deenitions in terms of Abstract State Machines, which have a simple but precise semantic foundation. As a consequence our JVM models can be veriied and validated by machine supported mathematical analysis and standard simulation techniques. Furthermore, due to their abstract nature, the models can serve as a platform independent basis for the evaluation and comparison of diierent JVM implementations.