| The aim of information integration is to build sophisticated systems by making use of available information resources, which including the computing resources, to fullest extent and by pushing costly operations to these sources as much as possible. What the queries integration systems do is to create a unified query interface, including query languages and schema that queries built on, and users can query multi-sources through the unified query interface.There are some shortages in current implements of query integration systems. Firstly, the organization of data sources can't meet the requirement of some applications. Some implements need a middle language to express the definition with multi-sources queries characteristics, with which we can do some optimization reasoning expediently. Thirdly, current implements work little research in distributed factors and related optimization algorithm.In this thesis, base on the traditional database framework, we propose and implement a Query Graph-based Heterogeneous Sources Framework. Based on this architecture, we research in some aspect of query integration system to a quite deep extent and implement a prototype of query integration system. We organize data sources with the structure of virtual sources, which is flexible to use in some scenario that current implements can't be used in. We use SQL and XQuery as the common query interface of distributed heterogeneous sources. Also, we define a middle algorithm, Enhanced Bushy Tree to limit traditional Bushy tree's search space and enhance the performance of distributed query execution. One more research in the analysis and optimization strategy of distributed factor is also referred in this thesis. We also give some example based on this architecture at last of this thesis.The example given at last show the successful design and implementation of our Heterogeneous Sources Framework, and additional quantitative performance measure result is available at last. |
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