Efficient Querying of Distributed Resources in Mediator Systems

This work investigates the integration of heterogeneous resources, such as data and programs, in a fully distributed peer-to-peer mediation architecture. The challenge in making such a system succeed at a large scale is twofold. First, we need a simple concept for modeling resources. Second, we need efficient operators for distributed query execution, capable of handling well costly computations and large data transfers. To model heterogeneous resources, we use the model of table with binding patterns. To exploit a resource with restricted binding patterns, we propose an efficient BindJoin operator, optimized for minimizing large data transfers and costly computations. Furthermore, the proposed BindJoin operator delivers most of its output in the early stages of the execution, which is an important asset in a system meant for human interaction. Our experimental evaluation validates the proposed BindJoin algorithm on queries involving expensive programs.