Cellular array architecture for relational database implementation

The design of high performance database machine architectures is a process wherein the mutual interaction of algorithms, data structures, and technology determines the final result. In the paper fully parallel algorithms for implementing the relational algebra operators are presented. Special emphasis is put on SELECT, PROJECT and JOIN. A relational database machine architecture based upon cellular arrays is proposed. A straight mapping between the relation structure and cellular array geometry, and the fact that cellular arrays can be easily implemented on a commercial scale as VLSI chips are the rationales of this proposal.     

使用ADO实现关系数据库访问层

在使用面向对象方法开发关系数据库应用系统时，人们希望对业务逻辑层开发人员隐藏在关系数据库中存取对象的细节，数据库访问层模式就是解决这个问题的一种设计模式。数据库访问层可以以多种方式实现，以ADO数据访问技术为基础，描述了一个关系数据库访问层的实现方案。     

基于iBATIS数据库访问技术的研究与应用

目前大多数软件开发都采用面向对象技术,而数据仍然保存在关系数据库中。由于对象模型和关系模型存在阻抗不匹配,因此实现对象与关系的映射已成为软件开发领域的关键问题。iBATIS采用O／R Mapping技术、XML技术和软件分层的设计思想,实现了一个有效的数据库访问中间件。选择iBATIS进行数据持久化,具有可开源、松耦合等特点,从而使系统的数据访问与应用逻辑分离开来。该技术的采用满足企业的开发需求,使系统具备可扩展性、可移植性、安全性、易维护性等。     

Time-based operators for relational algebra query languages

We present a new approach for historical relational algebra languages based upon generalized logic for Boolean and comparison operators and a temporal modification of the standard relational algebra operators. Historical versions of standard (snapshot) relational algebra operators based upon this generalized logic are presented. The temporal modification employs a logic that operates on sets of value/time-interval pairs and which can be applied to snapshot as well as historical databases. Our emphasis is that the generalized operators can be used to enrich existing historical query languages and to provide an easier and more natural time-based interface. Using the generalized operators, users can express their queries more naturally, succinctly and elegantly. Examples are presented which illustrate that the modified operators offer a good degree of flexibility in expressing different temporal requirements.     

关系代数派生算子语义表达式间等价性证明

关系代数的派生算子在关系数据库查询语言中得到了广泛应用。它们的语义有两种常见的表示方式,一种是基于原始算子的表达式,一种是基于一阶逻辑的表达式。但有关的文献资料都没有给出这两种表达式等价性的严格证明。文章尝试通过一系列等价变换,证明派生算子语义的这两种表达式间的等价性。从派生算子(主要是除算子)语义的原始算子表达式出发,根据关系代数表达式的特点,通过一步步的等价变换,得到派生算子语义的一阶逻辑表达式。所使用的变换方法能为关系代数表达式的正确性证明打下基础。     

基于Hibernate持久化层的设计与实现

在分层结构设计中,持久化层位于数据库层与业务逻辑层之间,实现了业务逻辑与数据访问的分离,给开发人员提供了便利。ORM框架是解决面向对象程序设计语言与关系数据库间存在互不匹配问题的中间方案。文中分析了几种常见持久化层实现技术的优缺点,通过对常用ORM框架技术的分析和比较,研究了一种基于Hibernate框架的ORM持久化层的设计与实现。为简化业务逻辑层调用,通过DAO模式实现了持久化层,提高了系统的开发效率和可重用性。基于Hibernate持久化层在Java企业级的应用开发中,具有较强的实用价值。     

Multikey, extensible hashing for relational databases

The design and implementation of a multikey, extensible hashing file addressing scheme and its application as an access method for a relational database are presented. This file organization was developed for Request, a testbed relational database-management system. It offers a viable alternative to indexed sequential files. Access operations, concurrency control, and relational operations are examined. Results of an experimental evaluation are reported     

A relational algebraic approach to protocol verification

Communications protocols are usually modeled by a pair of finite-state machines that generate the interaction between processes. Protocol verification is a procedure to validate the logical correctness of these interaction sequences and to detect potential design errors. A relational approach is proposed to represent a finite-state machine as a transition table. On this basis, the well-established theory of relational databases can be utilized to derive the global-state transitions of the system. Furthermore, logical errors of a protocol such as deadlocks, incomplete specifications and nonexecutable interactions can be formulated in terms of relational algebra. This approach has been implemented on the INGRES database system and applied to the verification of several protocols     

Temporal relational data model

This paper incorporates a temporal dimension to nested relations. It combines research in temporal databases and nested relations for managing the temporal data in nontraditional database applications. A temporal data value is represented as a temporal atom; a temporal atom consists of two parts: a temporal set and a value. The temporal atom asserts that the value is valid over the time duration represented by its temporal set. The data model allows relations with arbitrary levels of nesting and can represent the histories of objects and their relationships. Temporal relational algebra and calculus languages are formulated and their equivalence is proved. Temporal relational algebra includes operations to manipulate temporal data and to restructure nested temporal relations. Additionally, we define operations to generate a power set of a relation, a set membership test, and a set inclusion test, which are all derived from the other operations of temporal relational algebra. To obtain a concise representation of temporal data (temporal reduction), collapsed versions of the set-theoretic operations are defined. Procedures to express collapsed operations by the regular operations of temporal relational algebra are included. The paper also develops procedures to completely flatten a nested temporal relation into an equivalent 1 NF relation and back to its original form, thus providing a basis for the semantics of the collapsed operations by the traditional operations on 1 NF relations     

A New Integrated System of Logic Programming and Relational Database

Based on the study of the current two methods-interpretation and compilation-for the integration of logic programming and relational database,a new precompilation-based interpretive approach is proposed.It inherits the advantages of both methods,but overcomes the drawbacks of theirs.A new integrated system based on this approach is presented,which has been implemented on Micro VAX Ⅱ and applied to practise as the kernel of the GKBMS knowledge base management system.Also discussed are the key implementation techniques,including the coupling of logic and relational database systems,the compound of logic and relational database languages,the partial evaluation and static optimization of user‘s programs,fact scheduling and version management in problem-solving.     

A group-select operation for relational algebra and implicationsfor database machine design

A group-select operation has been defined for relational algebra. This operation is found to be useful for efficiently reducing expressions of nonprocedural relational languages that permit natural quantifiers. Conceptually, the operation first partitions a relation into blocks of tuples that have the same value for an attribute or attribute concatenation. It then extracts each block for which a specified number of tuples meet a specified condition. The quantity of tuples for the operation is specified by means of a natural quantifier. Performance of the group-select operation will be poor with conventional file processing, making the operation more suitable for use with a database machine with an associative memory     

A relational approach to querying data streams

Data streams are long, relatively unstructured sequences of characters that contain information such as electronic mail or a tape backup of various documents and reports created in an office. A conceptual framework is presented, using relational algebra and relational databases, within which data streams may be queried. As information is extracted from the data streams, it is put into a relational database that may be queried in the usual manner. The database schema evolves as the user's knowledge of the content of the data stream changes. Operators are defined in terms of relational algebra that can be used to extract data from a specially defined relation that contains all or part of the data stream. This approach to querying data streams permits the integration of unstructured data with structured data. The operators defined extend the functionality of relational algebra in much the same way that the join does relative to the basic operators select, project, union, difference, and Cartesian product     

Proceduralism and parallelism in specification languages

We discuss the advantages and limitations of the “nonprocedural” mode of expression, in the context of languages for programming, system specification, and database access. A language is introduced which has some relevance to all three of the above processes. The syntax of LEGOL is based on the relational algebra, but incorporates procedural control structures for use when the underlying application logic demands. Using this language, solutions can be suggested for some example stock-control problems which are difficult to handle in a purely non-procedural way.     

J2MEMicroDB: a new Open Source lightweight database engine for J2ME mobile devices

J2ME is the development platform for mobile devices with larger support and availability in the market right now. Due to the minimalist definition of this architecture it does include neither API’s for data persistence management, like object serialization, and relational database access nor standard APIs to access a remote host. This paper presents J2MEMicroDB, an Open Source software that implements object serialization, a local relational database engine on the mobile device and a remote database access protocol that allows access to any JDBC database. In the design and implementation of J2MEMicroDB specific requirements and limitation of mobile devices have been considered. Even some performance improvements have been developed, like BTree indexing structures which improves significantly the efficiency of the searches, as the presented cross-platform benchmarking proves.     

A suggestion for performance improvement in a relational database machine

Database machines are special purpose backend architectures that are designed to support efficiently database management system operations. An important problem in the development of database machines has been that of increasing their performance. Earlier research on the performance evaluation of database machines has indicated that I/O operations constitute a principle performance bottleneck. This is increasingly the case with the advances in multiprocessing and a growth in the volume of data handled by a database machine. One possible strategy to improve the performance of such a system which handles huge volumes of data is to store the data in a compressed form. This can be achieved by introducing VLSI chips for data compression so that data can be compressed and decompressed “on-the-fly”. A set of hardware algorithms for data compression based on the Huffman coding scheme proposed in an earlier work is described. The main focus of this paper is the investigation conducted by the authors to study the effect of incorporating such hardware in a special purpose backend relational database machine. Detailed analytical models of a relational database machine and the analytical results that quantify the performance improvement due to compression hardware are presented.     

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.     

PRISMA/DB: a parallel, main memory relational DBMS

PRISMA/DB, a full-fledged parallel, main memory relational database management system (DBMS) is described. PRISMA/DB's high performance is obtained by the use of parallelism for query processing and main memory storage of the entire database. A flexible architecture for experimenting with functionality and performance is obtained using a modular implementation of the system in an object-oriented programming language. The design and implementation of PRISMA/DB are described in detail. A performance evaluation of the system shows that the system is comparable to other state-of-the-art database machines. The prototype implementation of the system runs on a 100-node parallel multiprocessor     

Computerized relational model for powder technology: powder and process selection

Part of a complete expert-system software design for powder technology is presented. This part of the system deals with powder selection according to predetermined, recommended or required material properties, and specific powder characteristics. Then the optimum powder production, i.e processing, method is determined, which satisfies the requirements of the specified powder. For this purpose a detailed database relational model is developed, and the system's software modules are described. A relational model is formulated and a structured query language (SQL) is used in the detailed software design presented.     

分散控制系统(DCS)项目组态设计注意要点

分散控制系统厂家执行项目设计主要包括三大部分:DCS硬件设计、DCS组态设计、DCS网络安全设计;组态设计内容主要包括数据库设计、人机界面设计、控制逻辑设计。本文从组态软件组成总体要求、组态软件选型配置标准及工程项目实施各阶段组态总体规范与要求说明三方面进行阐述,以建立相应的组态设计执行标准,提高项目组态标准化,保障项目组态的安全。     

Designing and prototyping data-intensive applications in the Logresand Algres programming environment

The authors present an environment and a methodology for the design and rapid prototyping of data-intensive software applications, i.e., applications which perform substantial retrieval and update activity on persistent data. In the approach, the application is formally specified using Logres, a database language which combines object-oriented data modeling and rule-based programming. These specifications are translated into Algres, an extended relational algebra, thus yielding a rapid executable prototype. Algres programs embedded into a conventional programming language interface may be converted to conventional programs operating on a commercial relational system. This methodology helps automate the conversion from declarative requirements to imperative code, performing several tasks fully automatically and reducing the probability of human errors, while integrity constraints and application specifications are expressed in a declarative language, at a very high level of abstraction