Analysing the effect of network states in query cost estimation over the Internet

Query processing over the Internet has been proven to be one of the most difficult and important problems in modern e-data sharing society. In this new data processing environment, three major factors affect the cost of a query: network congestion situation, server states (server workload), and data/query complexity. We split the cost of queries into two parts: the cost of the network and the cost of servers and estimate each cost separately. We study the behaviour of the wide area network to derive the server states from the system contention states and the network congestion situation, and analyze two cases of network changing behaviour and propose different methods to deal with them respectively. So we can be more accurate to choose the best query plan according to the network situation, the system contention states and the server states at the query optimization stage.