Enhanced Type-based Component Compatibility Using Deployment Context Information

Abstract

Consistency and compatibility in component-based applications have been the subject of many methods and approaches, from formally sound ones with difficult practical implementation to pragmatic rules for comparing version meta-data which offer only weak guarantees. This is especially true of many industrial component frameworks in routine use. In this paper we contribute a formal description of a method which ensures application run-time type consistency, by performing type-based substitutability checks as part of the component binding and update processes. The method takes into account the environment of the currently deployed component version and uses its so-called contextual complement in the checks. This novel approach overcomes the limitations of the standard notion of compatibility by allowing non-contravariant differences on the required side of the componentʼs surface. The method was successfully implemented for the OSGi component framework, and in later parts of the paper we share the experiences gained through the implementation.