A client/server (C/S) system is a distributed system which consists of a collection of sites, connected together via communications network, in which some sites are client sites and others are server sites [2]. The logical division of responsibilities in the C/S system is that the client is the application or called the frontend, and the server is the DBMS or called the backend. Figure 1 shows a complex C/S environment where each site play the dual role of client and server. And, every application can access different remote databases on the network. The location independence or called transparency, however, is not supported, that is, applications need to specify the location path.
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