Most of the previous studies concerning checking the integrity constraints in distributed database derive simplified forms of the initial integrity constraints with the sufficiency property, since the sufficient test ...Most of the previous studies concerning checking the integrity constraints in distributed database derive simplified forms of the initial integrity constraints with the sufficiency property, since the sufficient test is known to be cheaper than the complete test and its initial integrity constraint as it involves less data to be transferred across the network and can always be evaluated at the target site （single site）. Their studies are limited as they depend strictly on the assumption that an update operation will be executed at a site where the relation specified in the update operation is located, which is not always true. Hence, the sufficient test, which is proven to be local test by previous study, is no longer appropriate. This paper proposes an approach to checking integrity constraints in a distributed database by utilizing as much as possible the local information stored at the target site. The proposed approach derives support tests as an alternative to the existing complete and sufficient tests proposed by previous researchers with the intention to increase the number of local checking regardless the location of the submitted update operation. Several analyses have been performed to evaluate the proposed approach, and the results show that support tests can benefit the distributed database, where local constraint checking can be achieved.展开更多
Integrity constraint is a formula that checks whether all necessary information has been explicitly provided. It can be added into ontology to guarantee the data-centric application. In this paper,a set of constraint ...Integrity constraint is a formula that checks whether all necessary information has been explicitly provided. It can be added into ontology to guarantee the data-centric application. In this paper,a set of constraint axioms called IC-mapping axioms are stated. Based on these axioms,a special ontology with integrity constraint,which is adapted to map ontology knowledge to data in relational databases,is defined. It＇s generated through our checking and modification. Making use of the traditional mapping approaches,it can be mapped to relational databases as a normal ontology. Unlike what in the past,a novel mapping approach named IC-based mapping is proposed in accordance with such special ontology. The detailed algorithm is put forward and compared with other existing approaches used in Semantic Web applications. The result shows that our method is advanced to the traditional approaches.展开更多
利用路径表达式导航 XML 查询是 XML 查询语言的共同特点。目前对 XML 路径表达式的计算有两种方法:一种是基于树遍历的方法,一种是路径连接方法。在路径连接方法中路径表达式的计算效率很大程度上依赖于路径表达式的长度。在对 XML 模...利用路径表达式导航 XML 查询是 XML 查询语言的共同特点。目前对 XML 路径表达式的计算有两种方法:一种是基于树遍历的方法,一种是路径连接方法。在路径连接方法中路径表达式的计算效率很大程度上依赖于路径表达式的长度。在对 XML 模式反映的完整性约束研究的基础上,本文提出了排他性包含约束的概念;给出了利用排他性包含约束缩短路径表达式的策略和算法,从而降低了路径连接的代价。通过分析比较,这种路径缩短策略是有效可行的。展开更多
文摘Most of the previous studies concerning checking the integrity constraints in distributed database derive simplified forms of the initial integrity constraints with the sufficiency property, since the sufficient test is known to be cheaper than the complete test and its initial integrity constraint as it involves less data to be transferred across the network and can always be evaluated at the target site （single site）. Their studies are limited as they depend strictly on the assumption that an update operation will be executed at a site where the relation specified in the update operation is located, which is not always true. Hence, the sufficient test, which is proven to be local test by previous study, is no longer appropriate. This paper proposes an approach to checking integrity constraints in a distributed database by utilizing as much as possible the local information stored at the target site. The proposed approach derives support tests as an alternative to the existing complete and sufficient tests proposed by previous researchers with the intention to increase the number of local checking regardless the location of the submitted update operation. Several analyses have been performed to evaluate the proposed approach, and the results show that support tests can benefit the distributed database, where local constraint checking can be achieved.
基金supported by the National Natural Science Foundation of China (60973089, 60873148)the Jilin Province Science and Technology Development Plan (20101501, 20100185)+1 种基金the Erasmus Mundus External Cooperation Window’s Project (EMECW): Bridging the Gap (155776-EM-1-2009-1-IT-ERAMUNDUS-ECW-L12)the Foundation of Key Laboratory of SCKE of Ministry of Education (450060326019)
文摘Integrity constraint is a formula that checks whether all necessary information has been explicitly provided. It can be added into ontology to guarantee the data-centric application. In this paper,a set of constraint axioms called IC-mapping axioms are stated. Based on these axioms,a special ontology with integrity constraint,which is adapted to map ontology knowledge to data in relational databases,is defined. It＇s generated through our checking and modification. Making use of the traditional mapping approaches,it can be mapped to relational databases as a normal ontology. Unlike what in the past,a novel mapping approach named IC-based mapping is proposed in accordance with such special ontology. The detailed algorithm is put forward and compared with other existing approaches used in Semantic Web applications. The result shows that our method is advanced to the traditional approaches.
文摘利用路径表达式导航 XML 查询是 XML 查询语言的共同特点。目前对 XML 路径表达式的计算有两种方法:一种是基于树遍历的方法,一种是路径连接方法。在路径连接方法中路径表达式的计算效率很大程度上依赖于路径表达式的长度。在对 XML 模式反映的完整性约束研究的基础上,本文提出了排他性包含约束的概念;给出了利用排他性包含约束缩短路径表达式的策略和算法,从而降低了路径连接的代价。通过分析比较,这种路径缩短策略是有效可行的。
