Flexible Language Interoperability

Virtual machines raise the abstraction level of the execution
environment at the cost of restricting the set of supported languages.
Moreover, the ability of a language implementation to integrate with
other languages hosted on the same virtual machine typically
constrains the features of the language. In this paper, we present a highly flexible
yet efficient approach to hosting multiple programming languages on an object-oriented
virtual machine. Our approach is based on extending the interface of each class with language-specific
wrapper methods, offering each language a tailored view of a given class. This approach can be
deployed both on a statically typed virtual machine, such as the JVM, and on a
dynamic virtual machine, such as a Smalltalk virtual machine.

We have implemented our approach to language interoperability on top of a prototype
virtual machine for embedded systems based on the Smalltalk object model, which provides
interoperability for embedded versions of the Smalltalk, Java, and BETA programming
languages.