Universal Query System Of Distributed Heterogeneous Database Integration

With continuous development of information technologies, the speed of information exploding has been to fast to be controlled by people. Science is the main power of productive force, which makes all industries of our country developing continuously. One main reason of that is the connection of establishing science information and information technology. science institute of every city had built science establishing system. And the questions followed that. Systems became so called information island, data can not be exchanged between city nodes. Therefore, information integration is a crucial problem to be solved immediately.With the scene of Science information unique query system, This thesis mainly discusses the traditional integration methods of distributed heterogeneous databases, analyzing advantages and disadvantages and application environments of each integration method. This thesis also provides a structure of the integrated query systems. It mainly introduces functional module of the middle ware layer, including design of metadata base and a resolution to semantic heterogeneous issues, functions and designing principle of the query dispatcher, functions and designing principle of database wrapper.Based on the traditional integration methods of distributed heterogeneous databases, this thesis introduces a solution which uses both thoughts of database integration middle ware and data warehouse. The middle ware layer mainly solves integration issues, and the data warehouse module provides a higher efficiency of system queries. Data warehouse defined in this thesis stores basic data of its sub databases; furthermore, it stores key fields of data records of the original databases. And that makes up the basic information data warehouse. When the terminal user submits a global query, corresponding data from the basic information data warehouse is firstly provided by the query system. And then judging from the basic information, the user makes a second accurate query. This time, query system gets data result from local sub databases. and makes a corresponding response. Consistency issues between the basic information data warehouse and its sub local database is also discussed in this thesis. Cache technology is introduced to the query dispatcher module in this integrated query system in the purpose of make the system more efficient. And Cache data exchange strategies of distributed query system is also analyzed in this thesis.