Recovery of client query work in the NetTraveler middleware system

This thesis presents NetTraveler, a Database Middleware System for Wide Area Networks that is designed to efficiently run queries over sites that are either mobile clients or enterprise servers. NetTraveler is designed to cope with dynamic Wide Area Networks where data sources go off-line, change location, have limited power capabilities, and form ad-hoc federations of sites. This thesis presents how NetTraveler can continue running a query when the client posing the query leaves, and then delivers the query results when the client returns. This thesis presents an implementation experience of NetTraveler using Web Services. The ideas of the design and implementation choices of NetTraveler are validated with a preliminary performance study. This study shows that NetTraveler can complete more queries per unit of time than middleware systems that cannot gracefully recover from contingencies during query execution caused by a client leaving the system. This study also shows that NetTraveler can handle a larger query load when compared to solutions based on previous approaches.