An architecture for software that adapts to changes in requirements

The goal of the research presented in this paper was to study a new software paradigm ± adaptive software ± in which the structure of an adaptive program is patterned upon the structure of an adaptive controller. Towards this aim, we implemented a domain-speci®c (object/target recognition) program (A Recon®gurable Architecture for Adapting to Changes in the Requirements (RAACR)) that can adapt to changes in software requirements through the incorporation of feedback. RAACR is a hierarchy of domains (blackboards). Each domain includes multiple knowledge sources (KSs) and a domain scheduler (DS). In response to feedback, KSs change their processing parameters, while DSs change the scheduling policy of the KSs. A generic communication mechanism is implemented on the CORBA compliant SPRING operating system. The adaptability of the program is evaluated quantitatively using a requirements volatility measure and the probability of correct recognition. Ó 2000 Elsevier Science Inc. All