Using Metadata Transformations to Integrate Class Extensions in an Existing Class Hierarchy

  • Markus Lumpe
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4279)


Class extensions provide a fine-grained mechanism to define incremental modifications to class-based systems when standard subclassing mechanisms are inappropriate. To control the impact of class extensions, the concept of classboxes has emerged that defines a new module system to restrict the visibility of class extensions to selected clients. However, the existing implementations of the classbox concept rely either on a “classbox-aware” virtual machine, an expensive runtime introspection of the method call stack to build the structure of a classbox, or both. In this paper we present an implementation technique that allows for the structure of a classbox to be constructed at compile-time by means of metadata transformations to rewire the inheritance graph of refined classes. These metadata transformations are language-neutral and more importantly preserve both the semantics of the classbox concept and the integrity of the underlying deployment units. As a result, metadata transformation provides a feasible approach to incorporate the classbox concept into programming environments that use a virtual execution system.


Virtual Machine Class Hierarchy Class Point Class Extension Text Section 
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© Springer-Verlag Berlin Heidelberg 2006

Authors and Affiliations

  • Markus Lumpe
    • 1
  1. 1.Department of Computer ScienceIowa State UniversityAmesUSA

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