Open Design and Language Transparency

Abstract

Distributed computing environments, such as ANSAware, CORBA, DCOM, and DCE achieve software component interoperability through specifying all public component interfaces in a common interface definition language. Programming language transparency is achieved by mapping these interface specifications to the programming language of choice. The language mapping defines the representation of an a priori agreed upon set of data types in the target programming language. The developer is restricted to this convention. This is, however, just the first step in achieving programming language transparency. By focusing on the CORBA standard we illustrate this mapping procedure. We develop and thoroughly analyze several design schemas for implementing cross-language method invocation with CORBA. From this discussion it will become clear that the current standard lacks support for user extensible programming language transparency. The CORBA standard does not allow the developer to efficiently and effectively interface arbitrary programming languages to CORBA middleware. Point solutions are possible, however, portable implementations of language mappings are not. We propose an addition to the current standard which would alleviate this problem and provide sufficient interfaces for other ORB extensions, such as request monitoring, debugging hooks, and custom marshaling, and interface language extensions.