An adaptive component is a component that is able to adapt its behavior to different execution contexts. Building an adaptive application is difficult because of component dependencies and the lack of language support. As a result, code that implements adaptation is often tangled, hindering maintenance and evolution. To overcome this problem, we propose a declarative approach to program adaptation. This approach makes the specific issues of adaptation explicit. The programmer can focus on the basic features of the application, and separately provide clear and concise adaptation information. Concretely, we propose adaptation classes, which enrich Java classes with adaptive behaviors. A dedicated compiler automatically generates Java code that implements the adaptive features. Moreover, these adaptation declarations can be checked for consistency to provide additional safety guarantees. As a working example throughout this paper, we use an adaptive sound encoder in an audio-conferencing application. We show the problems associated with a traditional implementation using design patterns, and how these problems are elegantly solved using adaptation classes.

Availability of data in a program determines computation stages. Incremental partial evaluation exploit these stages for optimization: it allows further specialization to be performed as data become available at later stages. The fundamental advantage of incremental specialization is to factorize the specialization process. As a result, specializing a program at a given stage costs considerably less than specializing it once all the data are available.We present a realistic and flexible approach to achieve efficient incremental run-time specialization. Rather than developing specific techniques, as previously proposed, we are able to re-use existing technology by iterating a specialization process. Moreover, in doing so, we do not lose any specialization opportunities. This approach makes it possible to exploit nested quasi-invariants and to speed up the run-time specialization process.This approach has been implemented in Tempo, a specializer for C programs that is publicly available. A preliminary experiment confirm that incremental that incremental specialization can greatly speed up the specialization process.