共查询到20条相似文献,搜索用时 703 毫秒
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k-匿名方法中准标识符的求解算法 总被引:4,自引:0,他引:4
k-匿名是保证视图安全的一种主要手段,如何找出正确的准标识符对k-匿名方法的有效性具有重要意义.针对这一问题,分析了不存在函数依赖和存在函数依赖两种情况下准标识符的组成特征,即当不存在函数依赖时,准标识符由视图间的公共属性组成,当存在函数依赖时,准标识符由视图间的公共属性和秘密信息包含的函数依赖关系的前件属性组成,在此基础上,给出了准标识符的通用求解算法,并用实验证明了算法的有效性和正确性. 相似文献
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k-匿名方法中相关视图集和准标识符的求解算法 总被引:2,自引:0,他引:2
准标识符是影响k-匿名方法有效性的关键因素.在视图发布过程中,求解准标识符所面临的问题是如何在已发布的视图集合中找出与待发布视图相关的全部视图.将已发布的视图集合与待发布的视图映射为一个超图,寻找相关视图集问题可被转化为在超图中求解特定结点间的全部通路问题.首先,给出了视图集向超图的映射方法及有关引理和定理,提出了基于超图的相关视图集求解算法;其次,研究了基本表中属性间不存在函数依赖和存在函数依赖两种情况下准标识符的组成结构,归纳出它们的特征,在此基础上,给出了基于相关视图集的准标识符求解算法.最后,对所提算法进行了正确性证明和时间复杂度分析. 相似文献
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一种多维数据库和多维视图模型 总被引:6,自引:1,他引:5
“多维”是数据仓库/OLAP应用普遍采用的模型化方法,文中提出了一种对多维数据库和在多维数据库上进行的查询/统计进行模型化的方法,并给出了模型的形式化定义,鉴于数据库本身与一次具体任务产生的结果两种对象的性质不同,特别区分了多维数据库和多维视图。多维数据库是对全部数据及其内在关系的全面描述;多维视图则是针对一次任务的对多维数据库的选择和重组。文中还着重讨论了多维数据库的划分问题,以函数依赖为主要依 相似文献
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生成式不完整多视图数据聚类 总被引:1,自引:0,他引:1
基于自表示子空间聚类的多视图聚类引起越来越多的关注. 大多数现有算法假设每个样本的所有视图都可获得, 然而在实际应用中, 由于各种因素, 可能会导致某些视图缺失. 为了对视图不完整数据进行聚类, 本文提出了一种在统一框架下同时执行缺失视图补全和多视图子空间聚类的方法. 具体地, 缺失视图是由已观测视图数据约束的隐表示生成的. 此外, 多秩张量应用于挖掘不同视图之间的高阶相关性. 这样通过隐表示和高阶张量同时挖掘了不同视图以及所有样本(即使是不完整视图样本)之间的相关性. 本文使用增广拉格朗日交替方向最小化(AL-ADM)方法求解优化问题. 在真实数据集上的实验结果表明, 我们的方法优于最新的多视图聚类算法, 具有更好的聚类准确度和鲁棒性. 相似文献
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本文研究关系模型中对象类视图关系模式的数据依赖问题。关系数据库中用一组表存放一个对象类的数据,并用视频实现对象类。本文分析该视图的列之间存在的函数依赖和多值依赖,并证明了类的所有单值和多值属性组成对象标识的多值依赖基。 相似文献
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XML(Extensive Markup Language)安全视图和查询重写是实现访问控制的关键技术.研究了基于XML递归安全视图的查询重写问题,分析了以前有关查询重写的研究工作,提出了一种基于XPath查询语言的能处理递归视图的查询重写算法,并对算法进行了分析,解决了当安全视图中存在递归时把查询进行有效重写的问题,避免了视图的物化和保存. 相似文献
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《Information Systems》1987,12(1):17-27
The term “security of a statistical database” usually refers to the problem of inference control. There are two main categories of inference controls in statistical databases: restrictions and perturbations. The influence of functional dependencies (which may hold among attributes in a statistical database) on restriction techniques is studied. For some techniques, either on the table or cell level, we demonstrate how these dependencies might lead to a compromise. It is shown that functional dependencies may decrease the effectiveness of several known inference controls (more precisely: output restriction controls). For some methods we give the way to overcome nondesirable influence of dependencies on control techniques. 相似文献
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In process-driven, service-oriented architectures, there are a number of important factors that hinder the traceability between
design and implementation artifacts. First of all, there are no explicit links between process design and implementation languages
not only due to the differences of syntax and semantics but also the differences of granularity. The second factor is the
complexity caused by tangled process concerns that multiplies the difficulty of analyzing and understanding the trace dependencies.
Finally, there is a lack of adequate tool support for establishing and maintaining the trace dependencies between process
designs and implementations. We present in this article a view-based, model-driven traceability approach that tackles these
challenges. Our approach supports (semi-)automatically eliciting and (semi-)formalizing trace dependencies among process development
artifacts at different levels of granularity and abstraction. A proof-of-concept tool support has been realized, and its functionality
is illustrated via an industrial case study. 相似文献
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Joachim Biskup Sebastian Link 《Annals of Mathematics and Artificial Intelligence》2011,63(3-4):213-255
We study inference systems for the combined class of functional and full hierarchical dependencies in relational databases. Two notions of implication are considered: the original notion in which a dependency is implied by a given set of dependencies and the underlying set of attributes, and the alternative notion in which a dependency is implied by a given set of dependencies alone. The first main result establishes a finite axiomatisation for the original notion of implication which clarifies the role of the complementation rule in the combined setting. In fact, we identify inference systems that are appropriate in the following sense: full hierarchical dependencies can be inferred without use of the complementation rule at all or with a single application of the complementation rule at the final step of the inference only; and functional dependencies can be inferred without any application of the complementation rule. The second main result establishes a finite axiomatisation for the alternative notion of implication. We further show how inferences of full hierarchical dependencies can be simulated by inferences of multivalued dependencies, and vice versa. This enables us to apply both of our main results to the combined class of functional and multivalued dependencies. Furthermore, we establish a novel axiomatisation for the class of non-trivial functional dependencies. 相似文献
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《Information Systems》1987,12(2):145-149
We introduce the class of “multi-relation dependencies” to capture the constraints among relations in a database. While the single relation dependencies are mainly used for database decomposition, the multi-relation dependencies may prove useful in studying the consistency issues regarding modification of data (i.e. insertions, deletions, and updates) in a decomposed database. We will discuss the inference problem of the multi-relation dependencies, and represent a complete set of inference rules for them. 相似文献
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Davide Alberto Albertini Barbara Carminati Elena Ferrari 《International Journal of Information Security》2017,16(1):75-89
In general, access control mechanisms in DBMSs ensure that users access only those portions of data for which they have authorizations, according to a predefined set of access control policies. However, it has been shown that access control mechanisms might be not enough. A clear example is the inference problem due to functional dependencies, which might allow a user to discover unauthorized data by exploiting authorized data. In this paper, we wish to investigate data dependencies (e.g., functional dependencies, foreign key constraints, and knowledge-based implications) from a different perspective. In particular, the aim was to investigate data dependencies as a mean for increasing the DBMS utility, that is, the number of queries that can be safely answered, rather than as channels for releasing sensitive data. We believe that, under given circumstances, this unauthorized release may give more benefits than issues. As such, we present a query rewriting technique capable of extending defined access control policies by exploiting data dependencies, in order to authorize unauthorized but inferable data. 相似文献
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一个基于视图的数据访问模型 总被引:1,自引:1,他引:1
多用户共享一个数据库必然存在一些安全隐患,须加以特定的控制措施以防止非法访问。提出一个基于视图的数据访问模型(VBAC),根据用户名创建与之联系的视图(视图成为该用户访问属于他的数据的惟一窗口),回收所有用户的权限,并将视图的访问权限授予给与之对应的用户,当一个用户登录系统,将他与对应的视图绑定起来,用户的数据访问通过视图间接完成,一旦回收视图的授权,与之对应的用户将不能对数据库进行任何存取。通过授权的数据视图,将用户对数据的操纵限定在特定的行和列,在用户和数据库之间建立信息安全防火墙。在Microsoft SQL Server 2000下测试了该模型的有效性。 相似文献
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Peter Dybjer 《Theoretical computer science》1984,33(1):95-105
Among the many different data dependencies defined, the so-called join dependencies play a central role, since they explicitly capture lossless join properties for relation schemes.In this paper we state some inference rules for join dependencies and embedded join dependencies. A set of two rules is shown to be complete for monadic join dependency inferences (inferences from a single dependency). Furthermore, it is shown that there is no finite set of inference rules that is complete for embedded join dependencies. 相似文献
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XML强多值依赖的推理规则集问题是解决不完全信息环境下XML数据依赖蕴涵问题的基础,是不完全信息环境下XML模式设计理论的关键问题之一。提出了XML Schema、符合XML Schema的不完全XML文档树等概念;基于子树信息等价和子树信息相容的概念提出了XML强多值依赖的定义及性质;给出了相应的推理规则集,并对其正确性和完备性进行了证明。研究成果为不完全信息环境下存在XSMVD的XML Schema设计奠定了基础。 相似文献
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The growing complexity of distributed systems in terms of hardware components, operating system, communication and application
software and the huge amount of dependencies among them have caused an increase in demand for distributed management systems.
An efficient distributed management system needs to work effectively even in face of incomplete management information, uncertain
situations, and dynamic changes. In this paper, Bayesian networks are proposed to model dependencies between managed objects
in distributed systems. The strongest dependency route (SDR) algorithm is developed for backward inference in Bayesian networks.
The SDR algorithm can track the strongest causes and trace the strongest routes between particular effects and its causes,
the strongest dependency of causes can be also achieved by the algorithm. Thus, the backward inference provides an efficient
mechanism in fault locating, and is beneficial for performance management. 相似文献
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To get more meaning of incomplete information,a predicate way is proposed torepresent the nulls.The concepts of functional and multivalued dependencies areextended in the environment which allows nulls in a database relation.The inferencerules which can be applied to the extended dependencies are investigated.Finally it isshown that the rules are complete for the family of extended functional and multivalueddependencies. 相似文献