Supporting cooperative applications

Cooperative applications which have started to emerge from CSCW research place new demands on the computer technology used to support them. These demands raise a number of fundamental questions about the way in which computing systems provide application support. This paper examines a number of issues surrounding the support of cooperative applications and how they impact both CSCW and computer science research. In particular, the relationship between cooperative applications and the supporting techniques of distributed systems and database technology are investigated. Cooperative applications question many of the design assumptions embodied within these techniques, and ask far reaching questions of the technology. Traditionally, support systems have been unaware of cooperative activities and have hidden the actions of others from each user. This paper examines the implications of this choice and the need to consider alternative approaches to the provision of systems support. The paper concludes by highlighting a number of issues which need to be addressed both by computer science and CSCW reseachers.     

嵌入式移动数据库同步系统的研究与实现

计算机技术的日益完善带动了嵌入式技术和数据存储技术的快速发展,数据库的应用不再局限于原来的区域,单纯为PC机设计的数据库技术对嵌入式系统的开发来说还远远不够。加大对嵌入式数据库,特别是嵌入式数据库同步系统的研究和开发力度是趋势所向。我们分析适用于SuperDB的嵌入式数据库同步系统,根据服务器端和用户端的需求来建立系统,最终完成数据库同步系统的运行。     

A configurable cryptography subsystem in a middleware framework for embedded systems

Computer and network security is becoming increasingly important as both large systems and, increasingly small, embedded systems are networked. Middleware frameworks aid the system developer who must interconnect individual systems into larger interconnected, distributed systems. However, there exist very few middleware frameworks that have been designed for use with embedded systems, which constitute the vast majority of CPUs produced each year, and none offer the range of security mechanisms required by the wide range of embedded system applications. This paper describes MicroQoSCORBA, a highly configurable middleware framework for embedded systems, and its security subsystem. It first presents an analysis of security requirements for embedded applications and what can and should be done in middleware. It then presents the design of MicroQoSCORBA’s security subsystem and the wide range of mechanisms it supports. Experimental results for these mechanisms are presented for two different embedded systems and one desktop computer that collectively represent a wide range of computational capabilities.     

Hierarchical control of multiple resources in distributed real-time and embedded systems

Real-time and embedded systems have traditionally been designed for closed environments where operating conditions, input workloads, and resource availability are known a priori, and are subject to little or no change at runtime. There is increasing demand, however, for adaptive capabilities in distributed real-time and embedded (DRE) systems that execute in open environments where system operational conditions, input workload, and resource availability cannot be characterized accurately a priori. A challenging problem faced by researchers and developers of such systems is devising effective adaptive resource management strategies that can meet end-to-end quality of service (QoS) requirements of applications. To address key resource management challenges of open DRE systems, this paper presents the Hierarchical Distributed Resource-management Architecture (HiDRA), which provides adaptive resource management using control techniques that adapt to workload fluctuations and resource availability for both bandwidth and processor utilization simultaneously. This paper presents three contributions to research in adaptive resource management for DRE systems. First, we describe the structure and functionality of HiDRA. Second, we present an analytical model of HiDRA that formalizes its control-theoretic behavior and presents analytical assurance of system performance. Third, we evaluate the performance of HiDRA via experiments on a representative DRE system that performs real-time distributed target tracking. Our analytical and empirical results indicate that HiDRA yields predictable, stable, and efficient system performance, even in the face of changing workload and resource availability.     

Systematic reliability analysis of a class of application-specific embedded software framework

Dramatic advances in computer and communication technologies have made it economically feasible to extend the use of embedded computer systems to more and more critical applications. At the same time, these embedded computer systems are becoming more complex and distributed. As the bulk of the complex application-specific logic of these systems is realized by software, the need for certifying software systems has grown substantially. While relatively mature techniques exist for certifying hardware systems, methods of rigorously certifying software systems are still being actively researched. Possible certification methods for embedded software systems range from formal verification to statistical testing. These methods have different strengths and weaknesses and can be used to complement each other. One potentially useful approach is to decompose the specification into distinct aspects that can be independently certified using the method that is most effective for it. Even though substantial-research has been carried out to reduce the complexity of the software system through decomposition, one major hurdle is the need to certify the overall system on the basis of the aspect properties. One way to address this issue is to focus on architectures in which the aspects are relatively independent of each other. However, complex embedded systems are typically comprised of multiple architectures. We present an alternative approach based on the use of application-oriented-frameworks for implementing embedded systems. We show that it is possible to design such frameworks for embedded applications and derive expressions for determining the system reliability from the reliabilities of the framework and the aspects. The method is illustrated using a distributed multimedia collaboration system.     

Four reference architectures for distributed database management systems

Five requirements for a centralized database management system and five additional requirements for a distributed database management system suggest definitions of software processors and schemas. These software processors and schemas can be organized into four reference architectures for distributed database management systems which permit comparisons of their advantages and disadvantages.     

铁路疾病预防控制数字化实验室研究

铁路疾病预防控制数字化实验室系统把各类检疫、检验、放免、放射及科研用的分析仪器,通过计算机实行联网,实现了各类仪器数据结果的实时自动接收、自动控制及综合分析,全面改善了实验室的工作现状,为疾病预防控制中心医疗质量提高争临床诊断提供了有力的保障.     

浅析数据库的安全性

数据库是数据管理的最新技术。使计算机科学的重要分支。随着信息资源成为各个部门的重要财富和资源．数据库系统的安全性也成为当前计算机安全最重要的问题．     

Impact of level-2 cache sharing on the performance and power requirements of homogeneous multicore embedded systems

In order to satisfy the needs for increasing computer processing power, there are significant changes in the design process of modern computing systems. Major chip-vendors are deploying multicore or manycore processors to their product lines. Multicore architectures offer a tremendous amount of processing speed. At the same time, they bring challenges for embedded systems which suffer from limited resources. Various cache memory hierarchies have been proposed to satisfy the requirements for different embedded systems. Normally, a level-1 cache (CL1) memory is dedicated to each core. However, the level-2 cache (CL2) can be shared (like Intel Xeon and IBM Cell) or distributed (like AMD Athlon). In this paper, we investigate the impact of the CL2 organization type (shared Vs distributed) on the performance and power consumption of homogeneous multicore embedded systems. We use VisualSim and Heptane tools to model and simulate the target architectures running FFT, MI, and DFT applications. Experimental results show that by replacing a single-core system with an 8-core system, reductions in mean delay per core of 64% for distributed CL2 and 53% for shared CL2 are possible with little additional power (15% for distributed CL2 and 18% for shared CL2) for FFT. Results also reveal that the distributed CL2 hierarchy outperforms the shared CL2 hierarchy for all three applications considered and for other applications with similar code characteristics.     

RDS在远程mdb数据库连接中的应用

随着计算机网络技术尤其是因特网技术的普及应用,远程数据库技术日益受到软件开发人员的重视,在Web网站后台管理系统和Intranet信息系统中,这种技术具有广阔的应用前景。远程数据库的连接方法是远程数据库技术的关键,尤其显得重要。本文作者根据自己从事信息管理系统开发的经验,给出在VB6.0编程中使用RDS组件与远程mdb数据库连接的方法。     

计算机系统在自动化仪器仪表中的应用

随着各领域技术的迅速发展和不断进步,计算机技术逐渐渗透到自动化控制技术中,其中,嵌入式计算机系统已经在仪器仪表领域获得了越来越多的应用。如今,自动化仪器仪表已具备＂工业IT＂的特征。本文首先介绍了我国仪器仪表控制系统的发展历程,阐述了嵌入式计算机系统的定义、特征、基本构架以及嵌入式计算机系统中的软件技术,对嵌入式计算机系统在仪器仪表中的应用进行了研究与分析,并展望了高级嵌入式系统对未来新型仪器仪表技术的支持及其前景。     

Selecting and implementing an embedded database system

Although embedded systems share many characteristics with their desktop and server counterparts, the unique advantages, limitations, and requirements of the applications they run demand a careful selection process and tailored implementation. The key strategy in choosing database tools for embedded systems is to focus on the application's requirements. Embedded database products vary widely from vendor to vendor. Some will do less than a particular application needs, some will do much more. By surveying the choices carefully, you can choose the tool that most closely matches your requirements. After choosing the operating system, hardware platform, and database software for a new embedded system, you must design a system that runs reliably with little or no human intervention. Unlike desktop and server systems, embedded systems cannot ask for operator help when the application encounters a problem. Finally, performance matters. Designing for performance up front, and evaluating it once you've built the application, is crucial. Fortunately, you can choose from a variety of techniques for evaluating and improving performance in database applications. To arrive at the best embedded-database-system solution, you must select the product that best matches your specific needs, then integrate that solution with your application. Start this process by evaluating which services your embedded application will provide     

Use of the SQL and RDA standards in data management

This paper discusses how existing and proposed Database Language SQL and Remote Database Access (RDA) standards can fulfill critical operational requirements for data management. SQL and RDA are but two components of a family of data management standards needed to meet requirements for emerging distributed processing systems. Requirements for needed capabilities such as object-oriented database, distributed database, and database export/import are discussed.     

嵌入式自适应安全关键中间件设计方法研究

由于嵌入式安全关键系统自身的特点和应用环境的特殊性,导致了设计嵌入式安全关键应用比一般的嵌入式实时应用要困难得多。在分析传统嵌入式实时中间件技术应用于嵌入式安全关键系统不足的基础上,提出了一种新的自适应安全关键中间件(ASCM)的设计方法,并对相应的体系结构和关键技术进行了讨论。另外,针对嵌入式安全关键系统运行环境的特殊性,重点讨论了一种端到端的自适应服务质量(QoS)管理机制。     

Fundamentals of integrated dictionary/ directory systems

One of the most potent tools available to support achievement of control over an organization's information resource is the Integrated Dictionary/Directory (D/D) System. Use of a D/D System can assist in data inventory management, cost control and improving resiliency to changing requirements. A D/D System is composed of a database (describing the information resource), retrieval and analysis capabilities, interfaces (enabling other software to access the D/D) and data management tools. Some D/D Systems are independent from other software packages; some either are dependent on or are actually embedded in other data management systems. D/D Systems provide functions to assist in interfacing the D/D to other software and loading the D/D with meta-data from other software. Use of a D/D System is a first step toward achieving control of the data resource.     

Design and Implementation of a Resource Manager in a Distributed Database System

This paper describes a system called Trends for managing IT resources in a production server environment. The objective of Trends is to reduce operational costs associated with unplanned outages, unbalanced utilization of resources, and inconsistent service delivery. The Trends resource manager balances utilization of multiple resources such as processor and disk space, manages growth to extend resource lifetimes, and factors in variability to improve temporal stability of balancing solutions. The methodology applies to systems in which workload has a strong affinity to databases, files, or applications that can be selectively placed on one or more nodes in a distributed system. Studies in a production environment demonstrate that balancing solutions remain stable for as long as the 9–12 months covered by our data. This work takes place in the context of the Lotus Notes distributed database system, and is based on analysis and data from a production server farm hosting over 20,000 databases.Norman Bobroff has been at IBM T.J. Watson Research Center since receiving his PhD in Physics in 1983. After working in optical lithography and laser metrology he joined computer science. His current interest is storage area networks and server performance.Lily Mummert is a researcher at IBM T.J. Watson Research Center in Hawthorne, NY. She received a PhD in Computer Science from Carnegie Mellon University in 1996. Her interests include distributed and mobile systems, self-managing systems, and distributed systems management.     

当年的动画片你还记得吗？

对数字化水资源管理信息系统中使用的分布式数据库技术进行详细的阐述,包括数据库的设计原则、系统结构、分布式查询和数据更新等内容,为水利部门进行查询、统计、分析对比以及防洪抗涝的预警提供保障.     

分布式数据库系统的安全因素及策略

计算机网络的高速发展推动着分布式数据库的发展,但如何保证开放网络环境中分布式数据库系统的安全是一个复杂的问题,需要进行认真分析研究。针对这一问题,阐述了分布式数据库系统存在的安全因素,分析了具体的安全策略,然后给出了基于Oracle数据库安全策略的实现。通过该安全策略的运用,可保证分布式数据库系统的安全运行。     

ADO.NET脱机数据的开放式并发控制研究

在数据库系统中,数据访问技术已经从连接模型发展到断开连接模型。目前,断开连接模型在应用中非常广泛,可以应用在分布式系统的开发、网络服务的应用、Web应用等。ADO.NET在断开连接模型下,可以支持脱机访问数据和数据处理,但也需要对脱机处理数据更新进行更加严密的控制。本文首先介绍ADO.NET脱机数据原理,接着探讨现有的三种开放式并发更新策略,并对此进行改进,提出新的更新并发策略。     

嵌入式虚拟化技术

计算机系统虚拟化技术是IT领域近几年的热点技术。虚拟化技术的下一步发展方向是嵌入式系统。嵌入式系统进行虚拟化是在嵌入式硬件平台和操作系统之间加入一层叫做虚拟机管理器的软件,由后者构造出可运行多种操作系统的虚拟机。国外多家公司和大学已对嵌入式虚拟化技术展开研究。嵌入式虚拟化的好处包括减少嵌入式系统开发成本、缩短产品上市周期、利于整合功能、减少功耗、软件资产保值和增强安全性与可靠性。嵌入式虚拟化技术面临的问题包括实时调度问题、嵌入式硬件平台多样性问题、电源管理问题以及跨虚拟机通信问题。嵌入式虚拟化技术将给嵌入式领域带来重大变化,值得关注。