区间约束及其代数查询语言

提出了区间约束和基于区间约束的代数查询语言。区间约束与密序约束相经,增加了简单的加减运算,具有更强的描述能力,同时区间约束元组有简洁,唯一的规范区间表示,文中给出了计算区间约束的规范区间表示的算法,针对区间约束关系,定义了基本代数操作的语法及语义,研究了代数查询语言,并证明代数约束查询语言满足封闭性,最后讨论了区间约束的实现与应用。     

Toward Practical Query Evaluation for Constraint Databases

Linear constraint databases (LCDBs) extend relational databases to include linear arithmetic constraints in both relations and queries. A LCDB can also be viewed as a powerful extension of linear programming (LP) where the system of constraints is generalized to a database containing constraints and the objective function is generalized to a relational query containing constraints. Our major concern is query optimization in LCDBs. Traditional database approaches are not adequate for combination with LP technology. Instead, we propose a new query optimization approach, based on statistical estimations and iterated trials of potentially better evaluation plans. The resulting algorithms are not only effective on LCDBs, but also applicable to existing query languages. A number of specific constraint algebra algorithms are also developed: select-project-join for two relations, constraint sort-join and constraint multi-join.     

Querying fuzzy relational databases through fuzzy domain calculus

In this paper we present a definition of a domain relational calculus for fuzzy relational databases using the GEFRED model as a starting point. It is possible to define an equivalent fuzzy tuple relational calculus and consequently we achieve the two query language levels that Codd designed for relational databases but these are extended to fuzzy relational databases: Fuzzy relational algebra (defined in the GEFRED model) and the fuzzy relational calculus which is put forward in this paper. The expressive power of this fuzzy relational calculus is demonstrated through the use of a method to translate any algebraic expression into an equivalent expression in fuzzy domain relational calculus. Furthermore, we include a useful system so that the degree to which each value has satisfied the query condition can be measured. Some examples are also included in order to clarify the definition. ©1999 John Wiley & Sons, Inc.     

区间约束数据库查询语言:ISQL

区间约束数据库可以统一处理空间和非空间数据,它基于关系数据库,增加了对区间约束数据的支持。为了管理区间约束数据,在这个模型基础上,提出一个区间约束数据语言ＩＳＱＬ．ＩＳＱＬ完全保留了数据库中非空间数据的ＳＱＬ查询能力,同时集成了对空间数据的管理。     

An evidential reasoning approach to attribute value conflictresolution in database integration

Resolving domain incompatibility among independently developed databases often involves uncertain information. DeMichiel (1989) showed that uncertain information can be generated by the mapping of conflicting attributes to a common domain, based on some domain knowledge. We show that uncertain information can also arise when the database integration process requires information not directly represented in the component databases, but can be obtained through some summary of data. We therefore propose an extended relational model based on Dempster-Shafer theory of evidence to incorporate such uncertain knowledge about the source databases. The extended relation uses evidence sets to represent uncertainty in information, which allow probabilities to be attached to subsets of possible domain values. We also develop a full set of extended relational operations over the extended relations. In particular, an extended union operation has been formalized to combine two extended relations using Dempster's rule of combination. The closure and boundedness properties of our proposed extended operations are formulated. We also illustrate the use of extended operations by some query examples     

A conceptual database design approach based on rules and heuristics

Conceptual and logical database design are complex tasks for non-expert designers. Currently, the popular data models for conceptual and logical database design are the entity–relationship (ER) and the relational model, respectively. Logical design methodologies for relational databases have relied on mathematically rigorous approaches which are impractical, or textbook approaches which do not provide the rich constructs to capture real applications. Consequently, designers have to use their intuition to develop their own rules and heuristics. There is a need, therefore, to develop practical rules and heuristics that can be used to handle the complexity of design in real applications. This paper proposes a realistic and detailed approach for conceptual design using the ER model for relational databases. The approach is based on four rules that specify the order in which various types of relationships must be modelled, three rules that pertain to detection of derived relationships, and three heuristics based on observation of constructs in real applications. The approach is illustrated by many examples.     

Slope Methods of Higher Order for the Inclusion of Complex Roots of Polynomials

We consider iterative methods for the inclusion of a simple complex root of a polynomial based on a slope in circular complex arithmetic. Combining the Newton method with the interval slope, two new algorithms of higher order in circular complex arithmetic are developed. The convergence analysis and numerical examples are included.     

关系模式下的XML数据存取技术研究

XML数据具有自描述性和半结构化特征,所以它能够从自身得到能够描述自己的类似于数据库的数据模式,并且对XML数据进行数据库存取。本文对利用关系模式来映射XML模式从而在关系数据库中存取XML数据的技术,进行了研究和初步应用。     

An extended algebra for constraint databases

Constraint relational databases use constraints to both model and query data. A constraint relation contains a finite set of generalized tuples. Each generalized tuple is represented by a conjunction of constraints on a given logical theory and, depending on the logical theory and the specific conjunction of constraints, it may possibly represent an infinite set of relational tuples. For their characteristics, constraint databases are well suited to model multidimensional and structured data, like spatial and temporal data. The definition of an algebra for constraint relational databases is important in order to make constraint databases a practical technology. We extend the previously defined constraint algebra (called generalized relational algebra). First, we show that the relational model is not the only possible semantic reference model for constraint relational databases and we show how constraint relations can be interpreted under the nested relational model. Then, we introduce two distinct classes of constraint algebras, one based on the relational algebra, and one based on the nested relational algebra, and we present an algebra of the latter type. The algebra is proved equivalent to the generalized relational algebra when input relations are modified by introducing generalized tuple identifiers. However, from a user point of view, it is more suitable. Thus, the difference existing between such algebras is similar to the difference existing between the relational algebra and the nested relational algebra, dealing with only one level of nesting. We also show how external functions can be added to the proposed algebra     

Handling fuzzy information in extended possibility‐based fuzzy relational databases

Two kinds of fuzziness in attribute values of the fuzzy relational databases can be distinguished: One is that attribute values are possibility distributions, and the other is that there are resemblance relations in attribute domains. The fuzzy relational databases containing these two kinds of fuzziness simultaneously are called extended possibility‐based fuzzy relational databases. In this paper, we focus on such fuzzy relational databases. We classify two kinds of fuzzy data redundancies and define their removal. On this basis, we define fuzzy relational operations in relational algebra, which, being similar to the conventional relational databases, are complete and sound. In particular, we investigate fuzzy querying strategies and give the form of fuzzy querying with SQL. © 2002 Wiley Periodicals, Inc.     

Prolog-based meta-rules for relational database representation andmanipulation

A Prolog-based experimental system for relational databases that is not defined from the viewpoint of any specific relational topic is proposed. The idea is that the experimental system can be used in many different contexts such as query optimization, data restructuring and database design. The definition is based entirely on the theoretical foundations of the relational model. The experimental system offers a well-defined environment for studying how other systems can be integrated with relational databases. The use of the experimental system in the context of different approaches to deductive databases is considered     

Queries on change in an extended relational model

A data model that allows for the storage of detailed change history in so-called backlog relations is described. Its extended relational algebra, in conjunction with the extended data structures, provides a powerful tool for the retrieval of patterns and exceptions in change history. An operator, Σ, based on the notion of compact active domain is introduced. It groups data not in predefined groups but in groups that fit the data. This operator further expands the retrieval capabilities of the algebra. The expressive power of the algebra is demonstrated by examples, some of which show how patterns and exceptions in change history can be detected. Sample applications of this work are statistical and scientific databases, monitoring (of databases, manufacturing plants, power plants, etc.), CAD, and CASE     

Ultrawrap: SPARQL execution on relational data

The Semantic Web’s promise of web-wide data integration requires the inclusion of legacy relational databases,¹ i.e. the execution of SPARQL queries on RDF representation of the legacy relational data. We explore a hypothesis: existing commercial relational databases already subsume the algorithms and optimizations needed to support effective SPARQL execution on existing relationally stored data. The experiment is embodied in a system, Ultrawrap, that encodes a logical representation of the database as an RDF graph using SQL views and a simple syntactic translation of SPARQL queries to SQL queries on those views. Thus, in the course of executing a SPARQL query, the SQL optimizer uses the SQL views that represent a mapping of relational data to RDF, and optimizes its execution. In contrast, related research is predicated on incorporating optimizing transforms as part of the SPARQL to SQL translation, and/or executing some of the queries outside the underlying SQL environment.Ultrawrap is evaluated using two existing benchmark suites that derive their RDF data from relational data through a Relational Database to RDF (RDB2RDF) Direct Mapping and repeated for each of the three major relational database management systems. Empirical analysis reveals two existing relational query optimizations that, if applied to the SQL produced from a simple syntactic translations of SPARQL queries (with bound predicate arguments) to SQL, consistently yield query execution time that is comparable to that of SQL queries written directly for the relational representation of the data. The analysis further reveals the two optimizations are not uniquely required to achieve a successful wrapper system. The evidence suggests effective wrappers will be those that are designed to complement the optimizer of the target database.     

PICQUERY: a high level query language for pictorial databasemanagement

A reasonably comprehensive set of data accessing and manipulation operations that should be supported by a generalized pictorial database management system (PDBMS) is proposed. A corresponding high-level query language, PICQUERY, is presented and illustrated through examples. PICQUERY has been designed with a flavor similar to QBE as the highly nonprocedural and conservational language for the pictorial database management system PICDMS. PICQUERY and a relational QBE-like language would form the language by which a user could access conventional relational databases and at the same time pictorial databases managed by PICDMS or other robust PDBMS. This language interface is part of an architecture aimed toward data heterogeneity transparency over pictorial and nonpictorial databases     

关系数据库数字水印技术

随着知识产权保护和信息安全技术的发展,关系数据库数据存在所有权问题,可以采用数字水印技术对其进行数字所有权管理。该文分析了关系数据库中的数据和图像、声频、视频等多媒体数据的区别及关系数据库水印的特点,探讨了几种关系数据库数字水印技术,还分析了对关系数据库数据水印技术的攻击方式和理想的关系数据库水印技术。水印关系数据库对数据库的安全有着广阔前景和实际应用价值。     

Bridging the gap between OWL and relational databases

Despite similarities between the Web Ontology Language (OWL) and schema languages traditionally used in relational databases, systems based on these languages exhibit quite different behavior in practice. The schema statements in relational databases are usually interpreted as integrity constraints and are used to check whether the data is structured according to the schema. OWL allows for axioms that resemble integrity constraints; however, these axioms are interpreted under the standard first-order semantics and not as checks. This often leads to confusion and is inappropriate in certain data-centric applications. To explain the source of this confusion, in this paper we compare OWL and relational databases w.r.t. their schema languages and basic computational problems. Based on this comparison, we extend OWL with integrity constraints that capture the intuition behind similar statements in relational databases. We show that, if the integrity constraints are satisfied, they need not be considered while answering a broad range of positive queries. Finally, we discuss several algorithms for checking integrity constraint satisfaction, each of which is suitable to different types of OWL knowledge bases.     

网站内容管理及个性化网页系统的研究与实现

针对现有内容管理系统在数据存储方面的问题,介绍了一个基于原生XML数据库和关系数据库的内容管理系统,这种方式充分利用了两种数据库的优势,提高了效率.同时应用数据挖掘技术,采用协同过滤算法,提供个性化网页服务,有助于赢得更多客户.     

Set-oriented data mining in relational databases

Data mining is an important real-life application for businesses. It is critical to find efficient ways of mining large data sets. In order to benefit from the experience with relational databases, a set-oriented approach to mining data is needed. In such an approach, the data mining operations are expressed in terms of relational or set-oriented operations. Query optimization technology can then be used for efficient processing.

In this paper, we describe set-oriented algorithms for mining association rules. Such algorithms imply performing multiple joins and thus may appear to be inherently less efficient than special-purpose algorithms. We develop new algorithms that can be expressed as SQL queries, and discuss optimization of these algorithms. After analytical evaluation, an algorithm named SETM emerges as the algorithm of choice. Algorithm SETM uses only simple database primitives, viz., sorting and merge-scan join. Algorithm SETM is simple, fast, and stable over the range of parameter values. It is easily parallelized and we suggest several additional optimizations. The set-oriented nature of Algorithm SETM makes it possible to develop extensions easily and its performance makes it feasible to build interactive data mining tools for large databases.     

基于本体的关系数据集成的查询处理

为实现异构关系数据库的语义集成,针对传统集成技术存在的问题,在对语义网等相关技术进行分析的基础上,研究基于本体的关系数据集成系统中的查询处理问题,提出了一种基于本体的关系数据库集成框架。设计了基于本体的关系数据的描述方法,使用本体作为集成的全局模式来描述关系模式的语义。设计了查询重写算法,该算法可以将基于全局模式的SPARQL查询重写为针对具体关系数据库的查询,从而实现对异构关系数据库的集成。实验表明,该算法具有良好的可扩展性。     

Efficient queries over Web views

Large Web sites are becoming repositories of structured information that can benefit from being viewed and queried as relational databases. However, querying these views efficiently requires new techniques. Data usually resides at a remote site and is organized as a set of related HTML documents, with network access being a primary cost factor in query evaluation. This cost can be reduced by exploiting the redundancy often found in site design. We use a simple data model, a subset of the Araneus data model, to describe the structure of a Web site. We augment the model with link and inclusion constraints that capture the redundancies in the site. We map relational views of a site to a navigational algebra and show how to use the constraints to rewrite algebraic expressions, reducing the number of network accesses. We show that similar techniques can be used to maintain materialized views over sets of HTML pages.