Research And Application Of Web-Services-Based Multi-Database Integrated Query System

There are several electromagnetic compatibility (EMC) test-units in our country. These test-units take on the tasks of testing many kinds of electronic devices' EMC and store the test data and correlative test criteria in their local EMC databases. These EMC databases are highly autonomic and their data schemas are always very similar to each other. Users or applications in these test-units usually need to query the shared data from several local databases and collect the data to make their analysis. Therefore, how to query these local databases integratedly are highly concerned by these test-units. Combined with the status and the requirement of these EMC test-units, this paper researches the problem of multi-database integrated query.This paper summarizes the styles of distributed application architectures and researches several distributed application techniques and multi-database integrate techniques. A new kind of distributed application technique named Web services is emphasized in the paper. According to the actual application background, key techniques to realize multi-database integrated query, such as global schema generating, schema translating, data collecting and global query realizing, are researched, and in the paper an EMC multi-database integrated system based on web services is presented and realized with Microsoft .NET Framework.The system presented in the paper adopts multi-tier architecture, which make the system of loosely coupled and highly extensible features. It conceals the geographic-distributing features of local databases and introduces a uniform global database view to users. Let alone this global view, local databases will keep their autonomy as usual. The system adopts a policy of partial data integrated and partial distributed to satisfy requirement more efficiently. Moreover, the system provides two kinds of interfaces: One kind is explorer-oriented thin-client interfaces, which supports users to query multi databases and explore their query result with an explorer. The other kind is web-service-based application interfaces, which supports the client application to realize multi databases query result through invoking the query interfaces provided by the system. According to a concrete application environment, this paper presents a query optimizing technique called keywords-based in versed index, which can prompt the system's query efficiency.