使用选择函数的亚蕴涵询问求值

本提出了使用选择函数的亚蕴涵询问求值方法以及依据此方法建立的询问求值算法ＩＶＡＬ。这种方法比Ｂｏｓｓｕ和Ｓｉｅｇａｌ的算法ＶＡＬ简便，效率高。ＩＶＡＬ和ＶＡＬ同时在ＳＵＮ－４上用Ｃ－Ｐｒｏｌｏｇ语言实现。本给邮了ＩＶＡＬ的理论依据，并把两种算法的执行效果作了比较。     

数据仓库的集合刷新维护算法

本文提出了一种版本控制集合刷新算法ＶＳＲＡ,它采用增量维护和批处理思想,首先根据原始数据的变化集合,计算出实体化视图的刷新集合,然后据此集合实体化视图,同时利用版本控制保持数据仓库与当前数据库状态的一致性,达到对数据仓库联机维护的目的。ＶＳＲＡ不但减少了数据仓库与数据库之间的通信开销,而且提高了实体化视
视图的刷新效率。严格的版本控制使用户可以随时使用数据仓库进行联机分析处理（ＯＬＡＰ）,并得到正确一     

实现函数式语言部分求值器的约束时间分析

文章研究部分求值技术中的约束时间分析（简称ＢＴＡ），介绍了一种高阶的函数式语言ＦＳＬ语言的部分求值器的ＢＴＡ。该部分求值器的ＢＴＡ由两个部分来实现：ＢＴＡ１和ＢＴＡ２，其目的是减少重复计算，提高部分求值的执行效率     

知识库中的空值探讨

分析了空值环境下的三种类型的查询策略，以及Datalog查询求值的Semi-Naive算法，给出了一个从子目标关系空值特性导出头关系空值特性的一种方法，使改进后的Semi-Navie算法能在带空值的EDB数据库中对Datalog查询进行正确求值。     

一个基于部分求值的增量式数据库引擎

文中介绍一个采用增量计算进行数据库操作的数据库引擎,阐述了利用部分求值技术实现增量式数据库查询的方法,给出了增量式数据库引擎的系统框架与实现方法。性能测试的实验结果的说明了这种数据库引擎的使用能够有效地提高数据库查询的效率。     

XBASE数据库文件与ORACLE之间的数据交换

本文介绍了Ｆｏｘｂａｓｅ、Ｆｏｘｐｒｏ等ＸＢＡＳＥ数据库中的数据文件同ＯＲＡＣＬＥ之间数据交换的方法。首先介绍如何使用ＳＱＬ＊ＵＬＯＡＤＥＲ将ＸＢＡＳＥ数据库的数据转储到ＯＲＡＣＬＥ数据库中。由于ＯＲＡＣＬＥ没有提供将ＯＲＡＣＬＥ数据库中的数据传储到ＸＢＡＳＥ数据库文件的工具，因此，本文然后给出了解决这一问题的方法。     

高阶函数式语言的部分求值器

本文提出了一种新的基于ＣＬＯＳＵＲＥ分析的高阶函数式语言的部分求值方法，对表达式中的高阶值采取了有效的抽象分析手段，从而提高了剩余程序的质量。文中给出了ＣＬＯＳＵＲＥ分析，抽象分析，标记和例化较完整的形式描述。     

ORACLE7分布式处理技术及二阶段提交分析

分布式数据库是目前引起广泛兴趣的一种应用系统实现方案，本文讨论了ＯＲＡＣＬＥ７数据库管理系统的分布式处理技术以及如何使用这一技术，分析了ＯＲＡＣＬＥ７分布式数据库系统的场地自治、位置透明和副本透明的方法，详细描述了保障全局数据库一致性的二阶段提交方法及恢复方法。     

知识库中的空值探讨

分析了空值环境下的三种类型的查询策略,以及Datalog查询求值的Semi-Naive算法,给出了一个从子目标关系空值特性导出头关系空值特性的一种方法,使改进后的Semi-Naive算法能在带空值的EDB数据库中对Datalog查询进行正确求值.     

子句间优化技术在语义缓存查询求值中的应用

缓存技术用来弥补网络通信能力的不足。语义缓存既缓存查询结果，也缓存查询语义，可更好节省网络开销。实用性是语义缓存技术产生和发展的基础，根据实用性要求，语义缓存查询求值所消耗的时空代价要远小于网络通信能力不足带来的时空代价，所以必须对求值算法进行优化。文章从语法一级分析求值算法存在的问题并给出了两级优化方法和实现技术，降低了算法复杂度，减少了对数据库的无效访问，使语义缓存技术向实用化迈进了一大步。     

An efficient indefiniteness inference scheme in indefinitedeductive databases

We introduce an inference scheme, based on the compilation approach, that can answer “true,” provable-false,” “indefinite,” or “assumable-false” to a closed query in an indefinite deductive database under the generalized closed world assumption. The inference scheme proposed in this paper consists of a representation scheme and an evaluation process that uses one of two groups of positive indefinite ground clauses (PIGC's) derivable from the database for a given query. These two groups of PIGC's are base-PIGC's and descendants of base-PIGC's. We prove that the set of base-PIGC's derivable from the database is sufficient to infer the indefiniteness of a query. This newly proposed method offers many advantages over the existing compilation method. This new method outperforms the existing one in terms of the cost of compilation, ease in the handling of updates, and efficiency in query evaluation     

Partial evaluation of queries in deductive databases

This paper presents some applications of partial evaluation method to a query optimization in deductive database. A Horn clause transformation is used for the partial evaluation of a query in an intensional database, and its application to multiple query processing is discussed. Three strategies are presented for the compatible case, ordered case and crossed case. In each case, partial evaluation is used to preprocess the intensional database in order to obtain subqueries which direct access to an extensional database.     

Evaluation and optimization of query programs in an object-orientedand symbolic information system

OASIS, a database programming environment that extends UNIX with the concept of persistent objects, is discussed. The OASIS query languages extend conventional database query languages with procedural methods and general control statements. As the complexity of the languages makes it difficult to device a query optimizer based on a universally applicable algorithm, each query in OASIS is optimized based on a collection of basic patterns for which each pattern is associated with a separation query optimization algorithm. The optimization techniques for a set of basic patterns consisting of iterative statements and a set of nested statements is described. The optimization techniques discussed include an extended decomposition algorithm, evaluation of multiple conditions, data dependence analysis, and optimization of queries with arbitrary nesting     

Partial evaluation of queries for bit-sliced signature files

Our research extends the bit-sliced signature organization by introducing a partial evaluation approach for queries. The partial evaluation approach minimizes the response time by using a subset of the on-bits of the query signature. A new signature file optimization method, Partially evaluated Bit-Sliced Signature File (P-BSSF), for multi-term query environments using the partial evaluation approach is introduced. The analysis shows that, with 14% increase in space overhead, P-BSSF provides a query processing time improvement of more than 85% for multi-term query environments with respect to the best performance of the bit-sliced signature file (BSSF) method. Under the sequentiality assumption of disk blocks, P-BSSF provides a desirable response time of 1 second for a database size of one million records with a 28% space overhead. Due to partial evaluation, the desirable response time is guaranteed for queries with several terms.     

An index selection method without repeated optimizer estimations

The index selection problem (ISP) concerns the selection of an appropriate index set to minimize the total cost for a given workload containing read and update queries. Since the ISP has been proven to be an NP-hard problem, most studies focus on heuristic algorithms to obtain approximate solutions. However, even approximate algorithms still consume a large amount of computing time and disk space because these systems must record all query statements and frequently request from the database optimizers the cost estimation of each query in each considered index. This study proposes a novel algorithm without repeated optimizer estimations. When a query is delivered to a database system, the optimizer evaluates the costs of various query plans and chooses an access path for the query. The information from the evaluation stage is aggregated and recorded with limited space. The proposed algorithm can recommend indexes according to the readily available information without querying the optimizer again. The proposed algorithm was tested in a PostgreSQL database system using TPC-H data. Experimental results show the effectiveness of the proposed approach.     

基于半连接的并行查询处理算法的研究

多元连接查询的并行执行是并行数据库的研究重点,传统的并行查询处理算法没有利用面向对象数据库及其查询的特点,算法效率较低.借鉴分布式数据库查询处理中基于半连接的优化思想,提出了基于半连接的并行查询处理算法.性能评价表明了其实用性和有效性.     

HVQS: The Hierarchical Visual Query System for Databases

This work describes the design and implementation of hierarchical visual query system (HVQS). It is a user interface for querying and browsing databases in a hierarchical database schema. HVQS enables users to use ahierarchical visual query , i.e. they can visually formulate a query and watch the query results on a few higher layers of database schema. This simplifies the query, reduces the failure rate, conserves query time, allows users to work on a database schema with wider scope, and helps users understand database content and focus on meaningful data using a top-down method. This work first gives an overview of the hierarchical visual query, and then describes the prototype of HVQS, defines a hierarchical graph for representing hierarchical database schema, and discusses the Query Manager and Visual Interface Manager of HVQS. Also described herein is the expressive power and semantics of HVQS query. Finally, a evaluation report of an experiment is given to demonstrate that HVQS improves the query success rate and facilitates users in query formulation.     

Fuzzy querying of incomplete, imprecise, and heterogeneously structured data in the relational model using ontologies and rules

In this paper, we present a new method, called multiview fuzzy querying, which permits to query incomplete, imprecise and heterogeneously structured data stored in a relational database. This method has been implemented in the MIEL software. MIEL is used to query the Sym'Previus database which gathers information about the behavior of pathogenic germs in food products. In this database, data are incomplete because information about all possible food products and all possible germs is not available; data are heterogeneous because they come from various sources (scientific bibliography, industrial data, etc); data may be imprecise because of the complexity of the underlying biological processes that are involved. To deal with heterogeneity, MIEL queries the database through several views simultaneously. To query incomplete data, MIEL proposes to use a fuzzy set, expressing the query preferences of the user. Fuzzy sets may be defined on a hierarchized domain of values, called an ontology (values of the domain are connected using the a kind of semantic link). MIEL also proposes two optional functionalities to help the user query the database: i) MIEL can use the ontology to enlarge the querying in order to retrieve the nearest data corresponding to the selection criteria; and ii) MIEL proposes fuzzy completion rules to help the user formulate his/her query. To query imprecise data stored in the database with fuzzy selection criteria, MIEL uses fuzzy pattern matching.     

网格环境下的数据库访问和集成

为了集成网格环境中的数据库资源,促进网格应用支持现有数据库的访问,提出一种基于服务的数据库访问和集成系统(GridDBAdmin)。GridDBAdmin为用户提供了虚拟的全局逻辑数据库视图,支持用户使用现有的SQL语言同时访问多个数据库。系统由元数据服务和网格虚拟数据库服务构成。其中元数据服务负责发现含有用户所需数据的数据库,网格虚拟数据库服务提供全局逻辑视图,通过分布式查询机制将用户的SQL请求分解到具体的数据库中并进行结果合并。对基于Globus和OGSA-DAI工具包开发的原型系统进行了测试,得到了较好的结果。