Research Of Multidatabase Based On Web Service

With the rapid development of the network and database technology, the needs for data sharing is getting stronger than ever before. Multidatabase system has rendered a very good solution to the integration of several distributed, heterogeneous and autonomous databases.The multidatabase system meets the needs of data sharing by shilding the physical and logical differnecs between databases.Multidatabases ever existed almost take CORBA as the base of system and communication integration, which often meet with such obstacles as implementation of new components for communication between systems when integrated systems needs interoperation. Web Service is a service oriented distributed computing module. On the basis of analysis and comparing with different theories and methods in integrating heterogeneous database systems, a new distributed multidatabase archietecture is proposed, which has such strongpoints as loose-coupling, cross-platform, cross-programming language, can be extended to Internet easily. Some self-contained and effecitive methods to encapsulate sub-functions of multidatabase into web services are suggested.There exists bottle neck in the transmission of massive data in the integrated system based on Web Service. On the basis of analysis of SOAP sending message and receiving message processes, specific methods such as block-coded, persistant connection and message receiving based on perfect hash table are proposed and verified to be effecitive after analyzing the performance of SOAP which is the communication protocol of Web Service under massive data transmission. Analysis of TCP proves that TCP is some reason why the effectiveness of SOAP is low and some effective methods such as make active-closed client are proposed.An extended multidatabase prototype, named Panorama system, was designed and implemented partly with above methods. A detailed implementation of the local agent named WebLDA is introduced, which can extract data from databases from Internet, therefore provides transparent interoperability among web database sources and existing database management systems.