Location types for safe programming with near and far references

  • Authors:

  • Yannick Welsch;Jan Schäfer;Arnd Poetzsch-Heffter

  • Affiliations:

  • University of Kaiserslautern, Germany;University of Kaiserslautern, Germany;University of Kaiserslautern, Germany

  • Venue:
  • Aliasing in Object-Oriented Programming
  • Year:
  • 2013

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Abstract

In distributed object-oriented systems, objects belong to different locations. For example, in Java Remote Method Invocation (RMI), objects can be distributed over different Java virtual machines. Accessing a reference in RMI has crucially different semantics depending on whether the referred object is local or remote. Nevertheless, such references are not statically distinguished by the Java type system. This chapter presents location types, which statically distinguish far from near references. We present a formal type system for a minimal core language and develop a type inference system that gives maximally precise solutions satisfying further desirable properties. We prove soundness of the type system as well as soundness and correctness of the inference system. We have implemented location types as a pluggable type system for the ABS language, an object-oriented language with a concurrency and distribution model based on concurrent object groups. To facilitate programming with location types, we provide a tight integration of the type and inference system with an Eclipse-based integrated development environment (IDE) that presents inference results as overlays to the source code. The IDE drastically reduces the annotation overhead while providing full static type information to the programmer.