基于多决策值等价类的属性约简

针对决策信息系统属性约简问题,引入条件属性的多决策值等价类概念,给出实现属性约简的必要条件,提出一种基于多决策值等价类的属性约简算法.该算法以单个条件属性的等价类的基为升序,对条件属性进行排序,逐一选择排序后的条件属性合并,直至合并后的条件属性子集的正域为全域,进一步判断其是否独立且不可区分关系与原信息系统的不可区分关系是否相同.当条件满足时,该条件属性子集即为决策信息系统的属性约简.通过实例验证了该算法求解属性约简的有效性.     

基于交可约等价类的概念格属性约简

定义交可约等价类的概念, 研究基于交可等价类的概念格属性约简及其算法,并由此得到不同类型属性的特征。使用链表表示形式背景的逻辑结构并根据外延对象个数大小建立索引快速判断交运算对属性约简的有效性。根据属性对交运算的不同作用找出所有不必要属性,最终得到概念格的属性约简。     

CIMS信息集成平台中的OO视图模型

为了满足ＣＩＭＳ环境中信息集成的要求,本文为信息集成平台设计了一种具有集成功能的面向对象视图模型Ｉ－ＶＩＥＷ．Ｉ－ＶＩＥＷ对ＯＯ模型进行了扩充,定义了虚属性、虚对象的概念;引入了输入与隐藏机制和类派生机制,允许对对象的状态和行为进行提炼,能够很好地解决各类集成问题,如模式映射、评义冲突和模式合并与重构等。     

对象定向概念格的决策约简

研究了基于对象定向概念格的决策形式背景的属性约简的定义和方法。在对象幂集上引入一个等价关系,并介绍了相关性质。提出了决策形式背景的协调性的定义,进而利用等价关系给出了协调决策形式背景的属性约简定义。该定义下的属性约简集能保持由原属性集确定的所有等价类不变的最小属性子集,同时它也能保持所有对象定向概念的外延不变。利用辨识矩阵提出了一种用于计算所有属性约简集的方法。     

形式概念分析构建面向对象程序的类及类体系

基于形式概念分析提出构建面向对象程序中类及类体系结构新方法.利用形式概念分析重要性质:给定对象和属性的二元关系,形式概念分析能把所有由相关的对象集合和属性集合组成的概念构成概念格;在概念格上,高层的概念表示共性而低层的概念表示个性.通过对现有面向对象应用程序的分析,可以得到新的类及类体系.这样做的好处是:所得到的类体系不仅等价于应用程序最初的类体系,而且在新体系中对象只包含它真正需要的成员,没有冗余成员.自然地,该方法可以用来发现类体系设计的不足之处,也可为类体系重建提供重要的参考建议.     

基于类间区分度的属性约简方法

属性约简是粗糙集理论中最重要的研究问题之一。近年来,粗糙集理论下的属性约简问题引发了学者们广泛的关注。然而,大多数属性约简方法都是基于不可分辨或可分辨关系所提出的,属性约简的性能仅仅取决于等价类或近似集的变化,却忽略了不具有等价关系的对象所在的不同类簇间关系的变化情况。因此,引入了类间区分度的概念,相较于等价类和上下近似集而言,它可以反映类簇区分程度随属性变化而变化的情况。对类间重合度和类间区分度进行了解释及定义,并结合启发式搜索策略,提出了一种基于类间区分度的属性约简方法,实验验证了所提方法的有效性。     

不一致决策表信息熵约简与代数约简的核计算与转化

对不一致决策表,信息熵约简与代数约简有时会得到不同的属性约简和核属性,当前的方法多为先将不一致决策表转化为一致决策表,再对后者寻求高效算法.本文基于等价差别矩阵具有相同的核属性和属性约简的思想,提出一种以条件属性等价类构造简化的代数约简差别矩阵,从差别矩阵内部进行比较与分析,发现只须将信息熵约简差别矩阵中由同时为矛盾对象所产生的可辩识属性集剔除,即可转化为简化的代数约简差别矩阵,从而得到将信息熵约简核属性转化为代数约简核属性的新方法,理论分析与数值算例都验证了其正确性.     

基于Rough集的连续属性离散化方法

连续属性离散化是Rough集理论应用中面临的主要问题之一.提出了一种基于的Rough集连续属性离散化方法.首先提出主泛化决策等概念,在数据过滤方法的基础上,利用等价类的合并对属性离散化.实验表明,利用该方法对数据进行离散预处理后提取的规则具有较好的分类预测准确性.     

粗等价粒度下基于多种加速策略的增量式求核算法

提出一种全新的渐增式求核算法。首先基于全局等价类提出粗等价类概念并分析其性质,研究粗等价类下的求核与约简;深入研究3类粗等价类与核属性的内在联系,设计粗等价类下判断核属性的等价方法和渐增式求核方法,通过该方法可在一次增量计算中求得多个非核属性,从而设计双向剪枝策略;可从属性和实体双方面缩减计算域,无需遍历全部属性和实体,在无核情况下,剪枝策略仍然有效。设计多次Hash的属性增量划分算法来完成上述增量式计算,基于此给出完整的渐增式求核算法。最后用UCI中20个决策表及海量、超高维3类数据集从多个角度进行验证,实验结果证明了所提算法的有效性和高效性,其尤其适用于大型决策表,大多数情况下优于现有算法。算法可进一步作为新型约简和优化算法的基础。     

一种类间交互测试的约束型标记驱动Petri网模型

面向对象软件测试的主要问题是考虑类间交互的集成测试,交互测试能检查出对象间的消息传递产生的不可达路径.设计了一种约束型标记驱动Petri网(C-LDPN)模型描述对象间的消息交互,给出了UML协作图转换为C-LDPN的规则.在定义对象活跃点以及对象活跃格局概念的基础上,根据对象所关联的变迁得出对象状态集上的等价类,提出一种消除C-LDPN中分支冲突的类间交互测试用例生成算法,求出对象的每个等价类中所有的活跃点数,得出对象的总状态数,用对象的分割连接子分割对象的状态域得到可达性C-LDPN,用合并连接子合并子对象得到标准型C-LDPN,最终生成类间交互测试用例--标记-变迁路径(LTPaths).     

信息集成系统中的模式融合问题研究

将模式融合分为模式映射、主键-外键融合和用户自定义的完整性融合3个部分。模式映射将关系模式或其他模式映射为对象代理模式类，主键-外键映射采用新的模式融合算法，充分考虑对象代理模型的特点。提出了一个新的操作Merge来解决用户自定义的模式融合。该操作克服了其他模型的用户自定义模式限制难于融合的问题。在Smalltalk环境中实现了基于对象代理模型的模式融合系统，并给出应用实例。     

An evidential approach to query interface matching on the deep Web

Matching query interfaces is a crucial step in data integration across multiple Web databases. The problem is closely related to schema matching that typically exploits different features of schemas. Relying on a particular feature of schemas is not sufficient. We propose an evidential approach to combining multiple matchers using Dempster–Shafer theory of evidence. First, our approach views the match results of an individual matcher as a source of evidence that provides a level of confidence on the validity of each candidate attribute correspondence. Second, it combines multiple sources of evidence to get a combined mass function that represents the overall level of confidence, taking into account the match results of different matchers. Our combination mechanism does not require the use of weighing parameters, hence no setting and tuning of them is needed. Third, it selects the top k attribute correspondences of each source attribute from the target schema based on the combined mass function. Finally it uses some heuristics to resolve any conflicts between the attribute correspondences of different source attributes. Our experimental results show that our approach is highly accurate and effective.     

A Methodology for Structural Conflict Resolution in the Integration of Entity-Relationship Schemas

The integration ofinf ormation systems is becoming increasingly important. A common requirement in distributed data-intensive applications, such as data warehousing and data mining, is that the various databases involved be joined in a process called schema integration. The entity-relationship (ER) model or a variant of the ER model is often used as the common data model. To aid the schema conforming, merging and restructuring phases of the integration process, various transformations have been defined to map between various equivalent ER representations. In this paper, we describe a different approach to integrate ER schemas. We focus on the resolution of structural conflicts, that is, when related real-world concepts are modeled using different constructs in different schemas. Unlike previous work, our approach proposes to resolve the structural conflict between an entity type in one schema and an attribute in another schema and show that the other structural conflicts are automatically resolved. This reduces the manual effort required in integration. We give a detailed algorithm to transform an attribute in one schema into an equivalent entity type in another schema without any loss of semantics, that is, our transformation is both information preserving and constraint preserving.     

A conceptual schema-based temporal meta database schemas generation technique for 3D objects

In this paper, a temporal meta database for three-dimensional (3D) objects whose properties and relationships are supported by valid time is introduced. Based on our proposed temporal object-oriented conceptual schema model, a conceptual schema of the temporal meta database can be generated from a 3D graphical data source and other particular application requirements. Based on our proposed temporal object relational data model with attribute timestamping, logical schemas of the temporal meta database can be systematically and automatically generated from the conceptual schema. From the temporal meta database, non-temporal/temporal metadata about temporal 3D objects are available for temporal information system users. Convenient access using database languages such as SQL can be performed. Queries over 3D objects using a temporal object relational SQL are demonstrated.     

Cost-benefit analysis of data warehouse design methodologies

Methodologies for data warehouse design are increasing more and more in last years, and each of them proposes a different point of view. Among all the methodologies present in literature, the promising ones are the hybrid methodologies—because they represent the only way to ensure a multidimensional schema to be both consistent with data sources and adherent to user business goals—and those able to support the designer by providing some kind of automation. However, the results obtainable by the methodologies can differ substantially in terms of schema quality and required efforts. In this paper, we provide metrics for evaluating the quality of multidimensional schemata in reference to the effort spent in the design process and the automation degree of the methodology. As a case study, we apply our evaluation to the major emerging hybrid methodologies for data warehouse schema design.     

Uninterpreted Schema Matching with Embedded Value Mapping under Opaque Column Names and Data Values

Schema matching and value mapping across two heterogenous information sources are critical tasks in applications involving data integration, data warehousing, and federation of databases. Before data can be integrated from multiple tables, the columns and the values appearing in the tables must be matched. The complexity of the problem grows quickly with the number of data attributes/columns to be matched and due to multiple semantics of data values. Traditional research has tackled schema matching and value mapping independently. We propose a novel method that optimizes embedded value mappings to enhance schema matching in the presence of opaque data values and column names. In this approach, the fitness objective for matching a pair of attributes from two schemas depends on the value mapping function for each of the two attributes. Suitable fitness objectives include the euclidean distance measure, which we use in our experimental study, as well as relative (cross) entropy. We propose a heuristic local descent optimization strategy that uses sorting and two-opt switching to jointly optimize value mappings and attribute matches. Our experiments show that our proposed technique outperforms earlier uninterpreted schema matching methods, and thus, should form a useful addition to a suite of (semi) automated tools for resolving structural heterogeneity.     

基于源模式分裂的模式匹配算法

模式匹配就是在作为输入的模式中有对应语义关系的元素间产生一个映射.为了提高模式匹配的效率,提出了一种新型的模式匹配方法--源模式分裂模式匹配算法.它可以解决标准模式匹配难以解决的问题:1)源模式的某一个属性和多个目标模式的多个属性之间建立匹配关系;2)表格中的不同元组对应其他表格同一元组的不同属性值的匹配.在匹配过程中,该方法先搜索种类型属性,然后根据种类型属性建立选择条件,最后把源模式进行分裂形成视图,再重新生成候选匹配集合,从而提高模式匹配的质量.     

An Object Algebra Approach to Multidatabase Query Decomposition in Donají

This paper presents an approach to query decomposition in a multidatabase environment. The unique aspect of this approach is that it is based on performing transformations over an object algebra that can be used as the basis for a global query language. In the paper, we first present our multidatabase environment and semantic framework, where a global conceptual schema based on the Object Data Management Group standard encompasses the information from heterogeneous data sources that include relational databases as well as object-oriented databases and flat file sources. The meta-data about the global schema is enhanced with information about virtual classes as well as virtual relationships and inheritance hierarchies that exist between multiple sources. The AQUA object algebra is used as the formal foundation for manipulation of the query expression over the multidatabase. AQUA is enhanced with distribution operators for dealing with data distribution issues. During query decomposition we perform an extensive analysis of traversals for path expressions that involve virtual relationships and hierarchies for access to several heterogeneous sources. The distribution operators defined in algebraic terms enhance the global algebra expression with semantic information about the structure, distribution, and localization of the data sources relevant to the solution of the query. By using an object algebra as the basis for query processing, we are able to define algebraic transformations and exploit rewriting techniques during the decomposition phase. Our use of an object algebra also provides a formal and uniform representation for dealing with an object-oriented approach to multidatabase query processing. As part of our query processing discussion, we include an overview of a global object identification approach for relating semantically equivalent objects from diverse data sources, illustrating how knowledge about global object identity is used in the decomposition and assembly processes.     

Efficient query processing in integrated multiple object databaseswith maybe result certification

Within integrated multiple object databases, missing data occurs due to the missing attribute conflict as well as the existence of null values. A set of algorithms is provided in this paper to process the predicates of global queries with missing data. To provide more informative answers to users, the "maybe" results due to missing data are presented in addition to the "certain" results. The local "maybe" results may become "certain" results via the concept of object isomerism. One algorithm is designed based on the centralized approach in which data are forwarded to the same site for integration and processing. Furthermore, to reduce the response time, localized approaches evaluate the predicates within distinct component databases in parallel. The object signature is also applied in the design to further reduce the data transfer. These algorithms are compared and discussed according to the simulation results of both the total execution and response times. Alternately, the global schema may contain multi-valued attributes with values derived from attribute values in different component databases. Hence, the proposed approaches are also extended to process the global queries involving this kind of multi-valued attribute