Scheduling cooperative transactions in distributed database systems

Scheduling transactions in advanced applications of distributed database systems, such as real-time distributed groupware systems and network management systems, are different from that in traditional database systems. In this paper, we propose new scheduling models, LWL for coordinating cooperative activities in real-time distributed groupware systems, and GTM for providing interoperability to network management systems, respectively.     

专题数据库导航系统的动态实现与数据更新

本文介绍了作者实现本馆专题数据库导航系统的方案,特别是对导航数据的更新研究,并讨论了扩充导航数据库内容的一些经验.提出了动态管理导航数据库的思路--即利用导航系统的管理模块对导航数据库内容进行扩充和编辑.最后,讨论了利用网络资源聚合技术RSS的必要性与可行性.     

Object-oriented decomposition for distributed systems

Conventional object-oriented design methodologies lead to a hierarchy of classes, but do not suggest which classes/objects should be loaded on which processors in a distributed system. We present the Decomposition Cost Evaluation Model (DCEM) as an approach to this problem. DCEM brings the mapping problem to a higher level of abstraction where the question is which classes, rather than which tasks, should be loaded on which processors. To support these decisions we define communication and computation cost functions for objects, classes, and hierarchies.We then introduce Confined Space Search Decomposition (CSSD) which enhances parallel operations of applications utilizing a tree topology for the processor interconnection scheme. To reduce the penalties of load imbalance, we include a distributed dynamic load balancing heuristic called Object Reincarnation (OR) in which no additional communication costs are incurred.     

Holistic schedulability analysis for distributed hard real-time systems

This paper extends the current analysis associated with static priority pre-emptive based scheduling to address the wider problem of analysing schedulability of a distributed hard real-time system; in particular it derives analysis for a distributed system where tasks with arbitrary deadlines communicate by message passing and shared data areas. A simple TDMA protocol is assumed, and analysis developed to bound not only the communications delays, but also the delays and overheads incurred when messages are processed by the protocol stack at the destination processor. The paper illustrates how a window-based analysis technique can be used to find the worst-case response times of a distributed task set. An extended example illustrating the application of the analysis is presented.     

The design of software for distributed control systems

The use of a network of computers rather than a large centralised computer can simplify the installation, commissioning, maintenance and the eventual replacement of computer-based control systems. To ensure that these benefits are realised in practice, a Central Electricity Generating Board project has been initiated to produce a standard software system, called CUTLASS, for implementing distributed control and instrumentation systems in power stations. This article describes a prototype network that has been implemented to evaluate the main design concepts of this standard software system.     

Efficient checkpointing procedures for fault tolerant distributed systems

A classical approach for achieving fault tolerance in distributed systems is based on the incorporation of efficient and fault tolerant procedures for checkpointing and recovery in such systems. We propose two checkpointing procedures, which can be initiated by any process in the system or upon failure of one or more component processes. Our procedures return the most recent and consistent checkpoints for the processes initiating the procedure, and do not interfere with the progress of the distributed system application. Furthermore, our procedures guarantee that a consistent checkpoint will be obtained when they terminate. Examples illustrating the application of the procedures are also provided.     

书目数据库中冗余数据的影响及解决方案

文章从书目数据库建设和管理的角度,指出了数据库中冗余数据产生的原 因及其对数据库造成的影响,提出了解决冗余数据的可行性方案,为图书馆书目数据库 的建设和共享提供了一些启示。     

Parset: A language construct for system independent parallel programming on distributed systems

Parallel programming on loosely coupled distributed systems involves many system dependent tasks such as sensing node availability, creating remote processes, programming inter-process communication and synchronization, etc. Very often these system-dependent tasks are handled at the programmer level. This has complicated the process of parallel programming on distributed systems. The portability of these programs is also severely affected. The programmer may also start his remote processes on heavily loaded nodes, thereby degrading the overall performance of the system. To overcome these difficulties, we introduce a language construct called parset at the programming level. Parset captures various kinds of coarse grain parallelism occurring in distributed systems. It also provides scalability to distributed programs. We show that this construct greatly simplifies writing programs on distributed systems providing transparency to various system dependent tasks.     

Intelligent dynamic systems

This paper concerns a new class of systems that are, on the one hand, dynamic systems, and on the other, intelligent systems, as their dynamics is described by knowledge representation, which is a common practice to use in intelligent systems, and the states are described by parameters and variables that have a logical or linguistic character. The case is considered when the rule system is used as a method of knowledge representation.     

从分布式数据库技术角度看我国文献资源共享存在的问题

通过分析分布式数据库的分片技术、资源配置技术和系统设计策略,研究了这些技术在资源建设、分配和管理等方面对文献资源共享系统的意义,指出了现有文献资源共享系统的不足,为完善我国资源共享系统建设提供了依据。     

Concurrency control scheme in multi-level secure database management systems

The most critical problem associated with implementing in multi-level secure database management systems (MLS/DBMSs) is a correct concurrency control under the constraints of multilevel security. This paper provides two concurrency control schemes, one based on multiversion scheme and the other based on the two-phase locking scheme.     

期刊数据的动态维护

期刊数据因不确定因素的影响，随时发生变化，因而期刊数据具有动态特征，本文就维护中的常见问题给予归纳并提示解决技巧。     

同行评审专家库动态管理及有效方法探讨

为消除科技论文同行评审过程中存在的弊端,缩短评审周期和获得参考价值较高的评审意见,结合科技期刊的自身特色和所在学科领域技术发展的特点,动态管理评审专家库.详细阐述在动态管理评审专家库的新增专家、更新专家信息和解聘专家方面实施的行之有效的方法:通过多种途径新增专家,完整收集专家的基本信息并动态跟踪、及时更新,准确定位专家的专业方向并动态跟踪、及时更新,定期评价专家的评审质量,勤于调整、适时解聘等.     

VINITI RAN abstract database: Prospects of information postprocessing using methods of data analysis

The All-Russian Institute of Scientific and Technical Information of the Russian Academy of Sciences (VINITI RAN) is active in the development of information and analysis technologies at a conceptual and practical level, using both its own and available domestic and foreign information resources. The aim of this paper is to describe (in the light of emerging trends in the institute) promising approaches to more in-depth information processing and analysis of available data, as well as to discuss the possibilities for creating new types of information products and services designed to support management decisions, not only in science and industry, but also, indirectly, in the economy as a whole.     

元搜索引擎信息服务的分布式数据挖掘

元搜索引擎通常缺乏自身独立的数据库后台,依托它的底层独立搜索引擎的数据库体系为用户提供信息服务,这种信息服务在满足用户复杂化、高级性检索需求上,表现出相当大的局限与不足,其改善手段之一是利用数据挖掘技术,根据元搜索引擎后台依托的数据库构成状况,选择分布式数据挖掘工具,较为科学、合理地建立其分布式数据挖掘系统,可利用CDM系统构建思想,基于先进的移动Agent技术,来提高挖掘系统的工作性能,并将一些关键技术充分地运用于系统中.     

Throughout evaluation in digital switching systems with distributed microprocessor control

The digital SPC switching systems with distributed μ-processor control discussed in this paper are large μ-processor systems providing a variety of telephone and data switching services. Throughput evaluation of such systems usually implies a significant innovation effort as concerns study tools and methods, i.e., simulation and calculation techniques, laboratory and field testing. This paper gives a concise review of these techniques and provides a bibliography.     

ABLEDATA: a database of products for the disabled

ABLEDATA (ABLE), a database funded by the National Institute on Disability and Rehabilitation Research (NIDRR) of the U.S. Department of Education and produced by the Adaptive Equipment Center of Newington Children's Hospital, Newington, Connecticut, provides information on more than 17,000 rehabilitation products from over 2,000 manufacturers in the U.S. and Canada. ABLE, which is available through BRS Search Service, BRS Colleague, and BRS After Dark, is a useful resource for rehabilitation professionals and others who wish to locate appropriate assistive devices for all categories of disabled persons.