A CONCURRENT, DISTRIBUTED ARCHITECTURE FOR DIAGNOSTIC REASONING

This paper demonstrates the feasibility of modeling concurrent diagnos tic reasoning (CDR) by means of the computational model of actors. Act ors have a value added on top of objects, because they include the pro perties of abstraction, modularity and reuse of objects but allow real ly concurrent and distributed architectures, in the sense that memory (the environment) is assumed not to be shared among actors. Whether co ncurrency really implies efficiency is still debated. We are more conc erned here with the actor-based design of the diagnostic reasoning mod el. As a testimony of the feasibility of our proposal, a concrete, act or-based diagnostic program is presented as a module for an intelligen t Tutoring System in the domain of school algebra. CDR is obtained fro m the coordinated behaviour of actors which possess limited local know ledge and accomplish the global goal of diagnostic reasoning by intera cting with each other. We examine how the 'traditional' approaches to student modeling, such as overlay and bug models, can be re-visited in a distributed perspective of computational actors and hew the latter view outperforms the previous ones.