Securing the distributed word processing network

There has been little concern for the security of stand-alone and shared-logic word processor systems although the threats are there and the loss from breaches of security can be very expensive. Word processors usually store processed information rather than data and modification or destruction of a document can lead to poor or delayed decisions. Inherent controls of paper-based systems are lost when the typing function is automated. Word processing networks are particularly vulnerable with reliance placed on the software system to secure documents. The weakest configuration in distributed word processing systems is in moderate size networks which cannot justify sophisticated hardware to support sophisticated operating systems and security software. Therefore, either additional physical security for each terminal or a more sophisticated authorization routine must be provided. The first is nearly impossible and the second rarely exists on these systems. As the trend toward hard disks for these units continues, the best solution may be the inclusion of a cryptographic routine.     

A survey of data processing steering committees

An approach to attempting to plan and control data processing functions is to use a steering committee. The committee composed of user, top management, and data processing representatives, is intended to bring a broad perspective to focus on systems issues.This paper summarizes the results of a survey on data processing steering committees. The empirical results indicate the actual practices of companies in utilizing steering committees. The reasons for implementing the approach structure, and operating processes are presented. Business experience with the success or failure of these committees is evaluated. The results are interpreted within the context of the current steering committee literature and practices.     

Decentralized management of bi-modal network resources in a distributed stream processing platform

This paper presents resource management techniques for allocating communication and computational resources in a distributed stream processing platform. The platform is designed to exploit the synergy of two classes of network connections—dedicated and opportunistic. Previous studies we conducted have demonstrated the benefits of such bi-modal resource organization that combines small pools of dedicated computers with a very large pool of opportunistic computing capacities of idle computers to serve high throughput computing applications. This paper extends the idea of bi-modal resource organization into the management of communication resources. Since distributed stream processing applications demand large volume of data transmission between processing sites at a consistent rate, adequate control over the network resources is important to ensure a steady flow of processing. The system model used in this paper is a platform where stream processing servers at distributed sites are interconnected with a combination of dedicated and opportunistic communication links. Two pertinent resource allocation problems are analyzed in detail and solved using decentralized algorithms. One is mapping of the processing and the communication tasks of the stream processing workload on the processing and the communication resources of the platform. The other is the dynamic re-allocation of the communication links due to variations in the capacity of the opportunistic communication links. Overall optimization goal of the allocations is higher task throughput and better utilization of the expensive dedicated links without deviating much from the timely completion of the tasks. The algorithms are evaluated through extensive simulation with a model based on realistic observations. The results demonstrate that the algorithms are able to exploit the synergy of bi-modal communication links towards achieving the optimization goals.     

虚拟分布式处理单元的设计与实现

针对过程仿真系统中对于DCS全仿真的需要,讨论了应用虚拟分布式处理单元的必要性,设计和实现了在PC机环境下运行的VDPU。对VDPU设计的整体架构和主要组成部分实现方法进行了研究,并讨论了应用VDPU进行控制系统全仿真研究对建模方法的要求。     

Evaluation of intranets in a distributed environment

The capture and dissemination of intra-organizational information is widely recognized to be essential for supporting operational and strategic corporate decision-making. Intranet technology has proven to be effective in accessing and disseminating intra-organizational data and knowledge, yet because of the novelty of intranets, very little research has been conducted to understand this technology in terms of its planning, management, and implementation. The objective of this study is to evaluate the role of intranet technology in a distributed environment with respect to its contributions to interconnectivity, information dissemination, process reengineering, organizational performance, and team collaboration.     

软件配置管理系统XML数据模型及原型研究

配置管理是软件开发管理中的重要支持活动。配置库管理是软件配置管理的核心任务之一。由于分布式配置库模型和internet的出现,对配置库间数据交换和访问提出了新的需求。该文首先了介绍配置库模型的一般概念及其核心数据组成,并基于XML定义了青鸟配置库数据模型,为同构/异构配置库模型间的数据交换提供支持。随后介绍了青鸟网上配置管理系统(JBCM_WEB)原型,研究了基于XML配置数据互操作和B/S方式的应用。     

Applying formal methods to standard development: The open distributed processing experience

Since their introduction, formal methods have been applied in various ways to different standards. This paper gives an account of these applications, focusing on one application in particular: the development of a framework for creating standards for Open Distributed Processing (ODP). Following an introduction to ODP, the paper gives an insight into the current work on formalising the architecture of the Reference Model of ODP (RM-ODP), highlighting the advantages to be gained. The different approaches currently being taken are shown, together with their associated advantages and disadvantages. The paper concludes that there is no one all-purpose approach which can be used in preference to all others, but that a combination of approaches is desirable to best fulfil the potential of formal methods in developing an architectural semantics for ODP.     

A system framework for open distributed processing

Emerging distributed applications increasingly require adequate tools and techniques for system- and application-level management. The integration of both aspects in an overall system framework is an important issue. This paper presents such a framework supporting advanced distributed applications in the context of the evolving Open Distributed Processing reference model. For system-level communication, an efficient subsystem providing advanced service capabilities is presented to cope with the increasing diversity of application service requirements. For application-level processing, a distributed object-based environment is offered. It implements location-independent invocation and object mobility and provides a high level of distribution transparency. The approach is augmented with tools and techniques for managing an overall application configuration.     

A time-optimal distributed sorting algorithm on a line network

We have achieved a strict lower time bound of n−1 for distributed sorting on a line network, where n is the number of processes. The lower time bound has traditionally been considered to be n because it is proved based on the number of disjoint comparison-exchange operations in parallel sorting on a linear array. Our result has overthrown the traditional common belief.     

Designing and scaling distributed VoD servers

Planning Video-on-Demand (VoD) services based on the server architecture and the available equipment is always a challenging task. We created a formal model to support the design of distributed video servers that adapt dynamically and automatically to the changing client demands, network and host parameters. The model makes giving estimations about the available throughput possible, and defines evaluation criteria for VoD services relating to utilization and load balance, video usage, client satisfaction and costs. The dynamism of the frame model originates from the possible state transitions which have to be defined in a core model. The core model is responsible for configuration recommendation which determines how clients are served depending on the properties of their requests, system configuration and system load. Furthermore, it decides on the optimal placement of the server components in the network. The usability of the model is illustrated on examples.     

An intelligent query processing for distributed ontologies

In this paper, we propose an intelligent distributed query processing method considering the characteristics of a distributed ontology environment. We suggest more general models of the distributed ontology query and the semantic mapping among distributed ontologies compared with the previous works. Our approach rewrites a distributed ontology query into multiple distributed ontology queries using the semantic mapping, and we can obtain the integrated answer through the execution of these queries. Furthermore, we propose a distributed ontology query processing algorithm with several query optimization techniques: pruning rules to remove unnecessary queries, a cost model considering site load balancing and caching, and a heuristic strategy for scheduling plans to be executed at a local site. Finally, experimental results show that our optimization techniques are effective to reduce the response time.     

A web-based sensor network system with distributed data processing approach via web application

We have proposed a Web-based sensor network constructed of Web-based sensor nodes and a remote management system. The Web-based sensor nodes consist of communication units and measurement devices with Web servers. The management system has intelligent processing and rule-based function to manage them flexibly via the Internet and performs various image analyses easily with Web application services. By distributing the image analyses to Web application services, our proposed system provides versatile and scalable data processing. We demonstrated that it can realize the desired image analyses effectively and perform complicated management by changing its operations depending on the results of analysis.     

A LOTOS based tutorial on formal methods for object-oriented distributed systems

The majority of formal methods for distributed systems have their origins in the 1980’s and were targeted at the early generations of distributed systems. However, modern distributed systems have new features not found in the early systems, e.g. they areobject-oriented, havemobile components, aretime sensitive and are constructed according to advanced system development architectures, e.g.viewpoints models. A major topic of current research is thus, how to enhance the existing formal techniques in order to support these new features. This paper gives a tutorial level review of this research area. We particularly focus on the process algebra LOTOS and consider how the technique can be reconciled with these new features. Howard Bowman, Ph.D.: He is a lecturer in the Computing Laboratory at the University of Kent at Canterbury. He received his Ph.D. from Lancaster University in 1991. His research focuses on applying formal techniques to the construction of distributed systems and he is a grant holder for a number of projects in this area. He is on the editorial board of the journal New Generation Computing and on the programme committees of a number of conferences, including, FORTE/PSTV. He was the programme co-chair of FMOODS’97, the IFIP conference on Formal Methods for Open Object Based Distributed Systems.     

The Vidboard: A video capture and processing peripheral for a distributed multimedia system

This paper describes a network-based video capture and processing peripheral, called the Vidboard, for a distributed multimedia system centered around a 1-Gbit/s asynchronous transfer mode (ATM) network. The Vidboard is capable of generating full-motion video streams having a range of presentation (picture size, color space, etc.) and network (traffic, transport, etc.) characteristics. The board is also capable of decoupling video from the real-time constraints of the television world, which allows easier integration of video into the software environment of computer systems. A suite of ATM-based protocols has been developed for transmitting video from the Vidboard to a workstation, and a series of experiments are presented in which video is transmitted to a workstation for display.     

Stochastic sensor activation for distributed state estimation over a sensor network

We consider distributed state estimation over a resource-limited wireless sensor network. A stochastic sensor activation scheme is introduced to reduce the sensor energy consumption in communications, under which each sensor is activated with a certain probability. When the sensor is activated, it observes the target state and exchanges its estimate of the target state with its neighbors; otherwise, it only receives the estimates from its neighbors. An optimal estimator is designed for each sensor by minimizing its mean-squared estimation error. An upper and a lower bound of the limiting estimation error covariance are obtained. A method of selecting the consensus gain and a lower bound of the activating probability is also provided.     

The network weather service: a distributed resource performance forecasting service for metacomputing

The goal of the Network Weather Service is to provide accurate forecasts of dynamically changing performance characteristics from a distributed set of metacomputing resources. Providing a ubiquitous service that can both track dynamic performance changes and remain stable in spite of them requires adaptive programming techniques, an architectural design that supports extensibility, and internal abstractions that can be implemented efficiently and portably. In this paper, we describe the current implementation of the NWS for Unix and TCP/IP sockets and provide examples of its performance monitoring and forecasting capabilities.     

An adaptable distributed query processing architecture

Traditionally, distributed query optimization techniques generate static query plans at compile time. However, the optimality of these plans depends on many parameters (such as the selectivities of operations, the transmission speeds and workloads of servers) that are not only difficult to estimate but are also often unpredictable and fluctuant at runtime. As the query processor cannot dynamically adjust the plans at runtime, the system performance is often less than satisfactory. In this paper, we introduce a new highly adaptive distributed query processing architecture. Our architecture can quickly detect fluctuations in selectivities of operations, as well as transmission speeds and workloads of servers, and accordingly change the operation order of a distributed query plan during execution. We have implemented a prototype based on the Telegraph system [Telegragraph project. Available from >]. Our experimental study shows that our mechanism can adapt itself to the changes in the environment and hence approach to an optimal plan during execution.     

Evaluation of distributed finite element algorithms on a workstation network

This paper discusses the design, implementation and evaluation of linear finite element programs that distribute their computations over a network of workstations. We consider five different algorithms based on direct, iterative and hybrid equation solvers, each of which partitions and maps the model domain across conventional network hardware. A software architecture based on the client-server model distributes the computations and, at the language level, Berkeley sockets enable communication between processes. We evaluate and describe the performance of these algorithms in terms of execution time and speed-up, and we conclude that distributed solvers, particularly those based on substructuring and static condensation, can be effective even on high-latency communication networks.     

Collaborative signal processing for target tracking in distributed wireless sensor networks

Target tracking, especially visual target tracking, in complex situations is challenging, which is always performed in single-view system. Because of the conflict between resolution and tracking range, however, single-view tracking is not robust and accurate. This paper presents a distributed multi-view tracking system using collaborative signal processing (CSP) in distributed wireless sensor networks (DWSNs). In the proposed tracking system, target detection and classification algorithms are based on single-node processing and target tracking is performed in sink node, whereas target localization algorithm is carried out by CSP between multisensor. For conquering the disadvantages of client/server based centralized data fusion, a progressive distributed data fusion are proposed. Finally, an indoor target tracking experiment is illustrated, and then tracking performance, execution time and energy consumption of progressive distributed data fusion are compared with client/server based centralized data fusion. Experimental results demonstrate that the CSP based distributed multi-view tracking system in DWSNs can accomplish multi-target extraction, classification, localization, tracking and association quickly and accurately with little congestion, energy consumption and execution time.     

Coach planning with opponent models for distributed execution

In multi-agent domains, the generation and coordinated execution of plans in the presence of adversaries is a significant challenge. In our research, a special “coach” agent works with a team of distributed agents. The coach has a global view of the world, but has no actions other than occasionally communicating with the team over a limited bandwidth channel. Our coach is given a set of predefined opponent models which predict future states of the world caused by the opponents’ actions. The coach observes the world state changes resulting from the execution of its team and opponents and selects the best matched opponent model based on its observations. The coach uses the recognized opponent model to predict the behavior of the opponent. Upon opportunities to communicate, the coach generates a plan for the team, using the predictions of the opponent model. The centralized coach generates a plan for distributed execution. We introduce (i) the probabilistic representation and recognition algorithm for the opponent models; (ii) a multi-agent plan representation, Multi-Agent Simple Temporal Networks; and (iii) a plan execution algorithm that allows the robust distributed execution in the presence of noisy perception and actions. The complete approach is implemented in a complex simulated robot soccer environment. We present the contributions as developed in this domain, carefully highlighting their generality along with a series of experiments validating the effectiveness of our coach approach.