In distributed object-oriented systems, objects belong to different
. 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
, which statically distinguish
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.