Web数据集成系统基于QC模型的物化视图选择

在Web数据集成系统中，物化视图能够有效地减少网络传输代价，提高系统的查询效率．如何选择查询进行物化，使得选中的查询满足集成层的空间限制，同时获取最大物化收益，成为集成系统中一个迫切需要解决的问题．传统方法没有考虑到海量XML查询之间的包含关系，其选择的物化视图中可能包含冗余的信息．针对上述问题，提出了①Web数据集成系统中海量查询集合的QC(query containment)模型，该模型能够捕捉查询之间最常见的包含关系；②基于QC模型的物化视图选择算法，算法考虑了物化视图选择相关的主要因素，包括查询提交的频率、空间代价、查询重写能力和查询结果的完备性，提出了查询位图的物化视图组织方式，从而获取更加合理的物化视图选择方案．实验结果证明了该方法的有效性．

QC Model Based Materialized View Selection in Web Data Integration

Materialized views can be used to reduce the expensive network transfer cost and improve the query efficiency significantly in a Web data integration system. How to select queries to materialize under space constraints, while at the same time maximizing the benefit of materialized views, becomes a fundamental problem. Traditional methods don't take the containment relationship among massive XML queries into account; hence the selected materialized views may contain redundant information. A new model and methods are proposed to overcome those problems. The contributions include (1) a QC (query containment) model to describe massive queries set in the Web data integration system, which captures the most common relationship (containment relationship) among the queries; (2) a method to select views from the queries set to materialize based on the QC model. This method considers the key related factors in the process of the view selection, including query frequency, query space cost, query rewriting capability and query result completeness, and proposes query bitmaps to organize the materialized views, thus generating a more reasonable views selection plan. Experimental results illustrate the validation of the method.