Integration of CORBA and object relational databases

CORBA is widely accepted as the open international standard for modelling and building comprehensive distributed systems. In most cases, CORBA architects have adopted relational databases for storage of persistent data. Among the issues that usually face architecture designers considering how to combine CORBA and standard relational database standards are fault tolerance, performance, and the extensibility and scalability of the systems. The research team involved with this paper found that the ODMG object database concept is useful to solve the issues encountered when integrating CORBA and relational database standards. The reference architecture, which the team devises, integrates CORBA and relational databases without compromise on the necessary transactional properties. The CORBA standard object transaction service and concurrency control service are reused. The team also develop an object relational data modelling tool—Latte—that supports the overall design intention as well the development paradigms for the proposed architecture. The implementation of the system is useful to CORBA, ODMG, and relational database architects because it provides a unified modelling and programming paradigm capable of solving the problems of managing mission-critical distributed data. Thus, we present a case study of combining different international standards to build a comprehensive system.     

Reasoning of fuzzy relational databases with fuzzy ontologies

A significant interest developed regarding the problem of describing databases with expressive knowledge representation techniques in recent years, so that database reasoning may be handled intelligently. Therefore, it is possible and meaningful to investigate how to reason on fuzzy relational databases (FRDBs) with fuzzy ontologies. In this paper, we first propose a formal approach and an automated tool for constructing fuzzy ontologies from FRDBs, and then we study how to reason on FRDBs with constructed fuzzy ontologies. First, we give their respective formal definitions of FRDBs and fuzzy Web Ontology Language (OWL) ontologies. On the basis of this, we propose a formal approach that can directly transform an FRDB (including its schema and data information) into a fuzzy OWL ontology (consisting of the fuzzy ontology structure and instance). Furthermore, following the proposed approach, we implement a prototype construction tool called FRDB2FOnto. Finally, based on the constructed fuzzy OWL ontologies, we investigate how to reason on FRDBs (e.g., consistency, satisfiability, subsumption, and redundancy) through the reasoning mechanism of fuzzy OWL ontologies, so that the reasoning of FRDBs may be done automatically by means of the existing fuzzy ontology reasoner.© 2012 Wiley Periodicals, Inc.     

The integrity constraints for similarity-based fuzzy relational databases

This paper first introduces a new definition for the conformance of tuples existing in a similarity-based fuzzy database relation. Then the formal definitions of fuzzy functional and multivalued dependencies are given on the basis of the conformance values presented here. These dependencies are defined to represent relationships between domains of the same relation that exist. The definitions of the fuzzy dependencies presented in this study allow a sound and complete set of inference rules. In this paper, we include examples to demonstrate how the integrity constraints imposed by these dependencies are enforced whenever a tuple is to be inserted or to be modified in a fuzzy database relation. © 1998 John Wiley & Sons, Inc.     

Towards an abstract theory of dependency constraints in relational databases

We introduce the notion of an FD system on a semilattice as a generalization of the concept of a closed set of functional dependencies, and we study lattice-theoretical properties of those objects. The notion of a table as an abstraction of relations of relational databases is also considered, and a generalization of relational algebra is presented; this offers a better perspective on the role played by Armstrong's relations. Finally, an application of this algebraic approach to dynamic databases is included.     

Reasoning about XML update constraints

We introduce in this paper a class of constraints for describing how an XML document can evolve, namely XML update constraints. For these constraints, we study the implication problem, giving algorithms and complexity results for constraints of varying expressive power. Besides classical constraint implication, we also consider an instance-based approach in which we take into account data. More precisely, we study implication with respect to a current tree instance, resulting from a series of unknown updates. The main motivation of our work is reasoning about data integrity under update restrictions in contexts where owners may lose control over their data, such as in publishing or exchange.     

Stability constraints and stability normal forms for temporal relational databases

This paper presents a new dynamic dependency and a new normal form. We give the concept of the stability constraint and establish complete axioms for stability constraints. In addition, we propose a stability normal form. A temporal third normal form can be losslessly decomposed into a sequence of stability constraints. Using the decomposition, the storage space can be reduced. The stability constraints allow to fill a suitable value into a null value. Thus, this null value therefore turns into a known value.     

关系数据库中聚合代数约束的高效发现算法——AAC-Hunter

针对如何更好地维护关系数据库的数据完整性以及帮助审计员找出违规的报销记录的问题，提出了自动发现聚合代数约束（AAC）的算法AAC-Hunter。AAC是一种定义在数据库中两列的聚合结果之间的模糊约束，作用于大多数而非全部记录上。AAC-Hunter首先枚举连接、分组和代数表达式来产生候选AAC，然后分别计算这些候选AAC的值域集合，最后输出AAC结果。但该方法无法应对海量数据带来的性能挑战，因此AAC-Hunter提出了一套启发式规则减小候选约束空间规模以及基于中间结果复用和消除平凡候选AAC的两个优化策略来加速候选AAC的值域集合计算。实验结果表明了对比不使用启发式规则和优化策略的基线算法，AAC-Hunter在TPC-H和European Soccer数据集上分别减小了95.68%和99.94%的约束发现空间，分别缩短了96.58%和92.51%的运行时间。可见AAC-Hunter具备有效性，能够提升审计应用的效率和能力。     

Keyword search in relational databases

This paper surveys research on enabling keyword search in relational databases. We present fundamental characteristics and discuss research dimensions, including data representation, ranking, efficient processing, query representation, and result presentation. Various approaches for developing the search system are described and compared within a common framework. We discuss the evolution of new research strategies to resolve the issues associated with probabilistic models, efficient top-k query processing, and schema analysis in relational databases.     

Object databases as generalizations of relational databases

One attractive approach to object databases is to see them as potentially an evolutionary development from relational databases. This paper concentrates on substantiating the technical basis for this claim, and illustrates it in some detail with an upwards-compatible extension of ANSI SQL2 for conventional objects. This could serve as a foundation for the development of higher-level facilities for more complex objects.     

XML数据库和关系数据库之比较

XML已经成为数据表示和交换的数据格式标准。随着大量XML文档的出现,应用数据库技术实现对XML数据的管理引起了越来越多研究者的兴趣。作为研究XML数据库技术的一个开始点,通过与关系数据库比较,可以深刻理解XML数据库与关系数据库的异同,进而为解决XML数据库所面临的问题,如为数据冗余控制、并发访问控制等提供必要的基础。两种数据库的比较是从数据模型、查询路径、完整性约束和规范化5个方面进行的,由于数据模型是数据库的基石,二者的数据模型从构造机制、名字的惟一性、空值、实体标识、实体问关系、文档顺序、数据结构的规则性、递归、数据自描述性等9个方面进行了详细讨论。     

An interface between object-oriented databases and relational databases

Currently relational databases are widely used, while object-oriented databases are emerging as a new generation of database technology. This paper presents a methodology to provide effective sharing of information in object-oriented databases and relational databases. The object-oriented data model is selected as a common data model to build an integrated view of the diverse databases. An object-oriented query language is used as a standard query language. A method is developed to transform a relational data definition to an equivalent object-oriented data definition and to integrate local data definitions. Two distributed query processing methods are derived. One is for general queries and the other for a special class of restricted queries. Using the methods developed, it is possible to access distributed object-oriented databases and relational databases such that the locations and the structural differences of the databases are transparent to users.     

Discovering causal rules in relational databases

This article explores the combined application of inductive learning algorithms and causal inference techniques to the problem of discovering causal rules among the attributes of a relational database. Given some relational data each field can be considered as a random variable and a hybrid graph can be built by detecting conditional independencies among variables. The induced graph represents genuine and potential causal relations as well as spurious associations. When the variables are discrete or have been discretized to test condi tional independencies supervised induction algorithms can be used to learn causal rules that is conditional statements in which causes appear as antecedents and effects as consequences. The approach is illustrated by means of some experiments conducted on different data sets.     

Ordered functional dependencies in relational databases

We extend the relational data model to incorporate linear orderings into data domains, which we call the ordered relational model. The conventional Functional Dependencies (FDs) are examined in the context of ordered relational databases by using the notion of System Ordering Independence (SOI), which refers to the desirable scenario that the ordering of tuples in a relation is independent of the implementation of the underlying DBMS. We also extend Armstrong's axiom system for FDs to object relations, which are a subclass of ordered relations that allow us to view tuples as objects. We formally define Ordered Functional Dependencies (OFDs) for the extended model by means of two possible extensions of domains, pointwise-orderings and lexicographical orderings. We first present a sound and complete axiom system for OFDs in the case of pointwise-orderings and then establish a sound and complete set of chase rules for OFDs in the case of lexicographical orderings. Our main result shows that the implication problems for both cases of OFDs are decidable, and that it is linear time for the case of pointwise-orderings.     

Unacceptable components in fuzzy relational databases

The existence of unacceptable components, which consist of unacceptable tuples and elements in attribute values, is shown in fuzzy relational databases. The unacceptable components are created by update operations, insertion, deletion, and modification. An unacceptable tuple in a relation is a tuple such that the degree of its not belonging to that relation is greater than that of its belonging to. The unacceptable tuple can be easily eliminated from relations. There are three kinds of unacceptable elements. One case of unacceptable elements is a redundant element created by insertion and modification. Another is an element created by a possible tuple value not at all or partially satisfying integrity constraints in insertion and modification. The other is an element created by a possible tuple value completely or partially satisfying update conditions in deletion. The unacceptable elements can be eliminated from relations without loss of information. As a result, we can obtain fuzzy relational databases without unacceptable components by a reasonable way. © 1996 John Wiley & Sons, Inc.     

Null values in nested relational databases

Summary The desire to extend the applicability of the relational model beyond traditional data-processing applications has stimulated interest in nested or non-first normal form relations in which the attributes of a relation can take on values which are sets or even relations themselves. In this paper, we study the role of null values in the nested relational model using an open world assumption. We extend the traditional theory and study the properties of extended operators for nested relations containing nulls. The no-information, unknown, and non-existent interpretation of nulls are discussed and the meaning of empty set is clarified. Finally, contrary to several previous results, we determine that the traditional axiomatization of functional and multivalued dependencies is valid in the presence of nulls.Currently with the Air Force Institute of Technology, AFIT/ENG, Wright-Patterson AFB, OH 45433, USAResearch partially supported by an IBM Faculty Development A ward and NSF grant DCR-8507224     

Dynamic non-dense indexes in relational databases

Indexes are a commonly used structure that provides fast access to the data. Their use imply storage and maintenance costs. This paper presents a technique to reduce index size, based on the elimination of tuple offsets in the classical B⁺ tree structure. It is shown that this technique gives advantages both in the tuple access and index maintenance.     

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.     

Losslessness and project-join constructibility in relational databases

Summary Checking a database scheme for the lossless join property with respect to a set, M, of multivalued dependencies (MVDs) is NP-hard. We prove that, for a class of MVDs that includes the set of projected full MVDs, this check can be performed in polynomial time. Even with a lossless database scheme and a consistent database, joining the set of relations in the database can take time and space that is exponential in the size of the relation finally obtained. Joining the set of relations of such a database can be performed in polynomial time if the database scheme is project-join constructible with respect to M. We prove that project-join constructibility, a stricter condition than the lossless join property, can be detected in a database scheme in polynomial time.