不一致数据无法正确反映现实世界,其上的查询结果内含错误或矛盾,而现有的很多不一致数据查询处理相关研究都存在信息丢失的问题.AQA(annotation based query answer)针对这一问题采用信任标签在属性级别上区分一致和不一致数据,避免了...不一致数据无法正确反映现实世界,其上的查询结果内含错误或矛盾,而现有的很多不一致数据查询处理相关研究都存在信息丢失的问题.AQA(annotation based query answer)针对这一问题采用信任标签在属性级别上区分一致和不一致数据,避免了信息丢失.但AQA假设记录在依赖左边属性上的分量可信,且只针对函数依赖一种约束,具有应用局限性.在综合约束(函数依赖、包含依赖和域约束)范围内、不确定属性任意的情况下扩展了AQA,重新审视了AQA的数据模型及其上的查询代数,讨论了任意约束在查询结果上的蕴含约束计算问题.实验结果表明,扩展后的AQA非连接类查询的性能和普通的SQL基本相同,连接查询经优化后性能接近普通SQL查询,但AQA不丢失信息,与部分同类研究相比有很大优势.展开更多
In this paper, we introduce a concept of Annotation Based Query Answer, and a method for its computation, which can answer queries on relational databases that may violate a set of functional dependencies. In this app...In this paper, we introduce a concept of Annotation Based Query Answer, and a method for its computation, which can answer queries on relational databases that may violate a set of functional dependencies. In this approach, inconsistency is viewed as a property of data and described with annotations. To be more precise, every piece of data in a relation can have zero or more annotations with it and annotations are propagated along with queries from the source to the output. With annotations, inconsistent data in both input tables and query answers can be marked out but preserved, instead of being filtered in most previous work. Thus this approach can avoid information loss, a vital and common deficiency of most previous work in this area. To calculate query answers on an annotated database, we propose an algorithm to annotate the input tables, and redefine the five basic relational algebra operations （selection, projection, join, union and difference） so that annotations can be correctly propagated as the valid set of functional dependency changes during query processing. We also prove the soundness and completeness of the whole annotation computing system. Finally, we implement a prototype of our system, and give some performance experiments, which demonstrate that our approach is reasonable in running time, and excellent in information preserving.展开更多
文摘不一致数据无法正确反映现实世界,其上的查询结果内含错误或矛盾,而现有的很多不一致数据查询处理相关研究都存在信息丢失的问题.AQA(annotation based query answer)针对这一问题采用信任标签在属性级别上区分一致和不一致数据,避免了信息丢失.但AQA假设记录在依赖左边属性上的分量可信,且只针对函数依赖一种约束,具有应用局限性.在综合约束(函数依赖、包含依赖和域约束)范围内、不确定属性任意的情况下扩展了AQA,重新审视了AQA的数据模型及其上的查询代数,讨论了任意约束在查询结果上的蕴含约束计算问题.实验结果表明,扩展后的AQA非连接类查询的性能和普通的SQL基本相同,连接查询经优化后性能接近普通SQL查询,但AQA不丢失信息,与部分同类研究相比有很大优势.
基金Supported by the National Natural Science Foundation of China under Grant No. 60603043the Program of Shanghai Municipal Education Commission under Grant No.06FZ030
文摘In this paper, we introduce a concept of Annotation Based Query Answer, and a method for its computation, which can answer queries on relational databases that may violate a set of functional dependencies. In this approach, inconsistency is viewed as a property of data and described with annotations. To be more precise, every piece of data in a relation can have zero or more annotations with it and annotations are propagated along with queries from the source to the output. With annotations, inconsistent data in both input tables and query answers can be marked out but preserved, instead of being filtered in most previous work. Thus this approach can avoid information loss, a vital and common deficiency of most previous work in this area. To calculate query answers on an annotated database, we propose an algorithm to annotate the input tables, and redefine the five basic relational algebra operations （selection, projection, join, union and difference） so that annotations can be correctly propagated as the valid set of functional dependency changes during query processing. We also prove the soundness and completeness of the whole annotation computing system. Finally, we implement a prototype of our system, and give some performance experiments, which demonstrate that our approach is reasonable in running time, and excellent in information preserving.
