A flexible mediation process for large distributed information systems

We consider distributed information systems that are open, dynamic and provide access to large numbers of distributed, heterogeneous, autonomous information sources. Most of the work in data mediator systems has dealt with the problem of finding relevant information providers for a request. However, finding relevant requests for information providers is another important side of the mediation problem which has not received much attention. In this paper, we address these two sides of the problem with a flexible mediation process. Once the qualified information providers are identified, our process allows them to express their interest in a request via a bidding mechanism. It also requires to set up a requisition policy, because a request must always be answered if there are qualified providers. This work does not concern pure market mechanisms because we counter-balance the providers' bids by considering their quality wrt a request. We validate our process on a set of simulations in the context of load balancing, which is a good indicator of the system's overall performance. The results show that the mediation process provides a very good long-run regulation of the system, in particular when providers can leave the system. However, load balancing is not the natural application of the flexible mediation and additional testing is required to show the generality of the approach to non-depletable resources.