Efficient execution strategies for mobile procedures querying distributed databases

Mobile agent technology raises a new dimension in distributed database processing. Of interest in this paper are mobile procedures querying multiple databases distributed over a network. In the used execution model, mobile execution can profit from both migration, reducing amount of transmitted data, and data prefetching at the most beneficial site. To achieve the lowest response time, an execution strategy should suggest an appropriate mix of agent migration, remote database access and data prefetching. Since there is no universal strategy suggesting the optimal execution in all cases, we must resign ourselves to possibly no optimal solution. The main achievement of this paper consists in proposing four dynamic execution strategies of different implementation complexity with different behavior under various conditions. The stategies were tested in the real Internet and their performance is compared to each other and to a classical centralized stationary approach