Declarative Infrastructure Configuration Synthesis and Debugging

There is a large conceptual gap between end-to-end infrastructure requirements and detailed component configuration implementing those requirements. Today, this gap is manually bridged so large numbers of configuration errors are made. Their adverse effects on infrastructure security, availability, and cost of ownership are well documented. This paper presents ConfigAssure to help automatically bridge the above gap. It proposes solutions to four fundamental problems: specification, configuration synthesis, configuration error diagnosis, and configuration error repair. Central to ConfigAssure is a Requirement Solver. It takes as input a configuration database containing variables, and a requirement as a first-order logic constraint in finite domains. The Solver tries to compute as output, values for variables that make the requirement true of the database when instantiated with these values. If unable to do so, it computes a proof of unsolvability. The Requirement Solver is used in different ways to solve the above problems. The Requirement Solver is implemented with Kodkod, a SAT-based model finder for first-order logic. While any requirement can be directly encoded in Kodkod, parts of it can often be solved much more efficiently by non model-finding methods using information available in the configuration database. Solving these parts and simplifying can yield a reduced constraint that truly requires the power of model-finding. To implement this plan, a quantifier-free form, QFF, is defined. A QFF is a Boolean combination of simple arithmetic constraints on integers. A requirement is specified by defining a partial evaluator that transforms it into an equivalent QFF. This QFF is efficiently solved by Kodkod. The partial evaluator is implemented in Prolog. ConfigAssure is shown to be natural and scalable in the context of a realistic, secure and fault-tolerant datacenter.

计算机网络组网形式与网络设备配置技术

当今网络时代,局域网在发挥着举足轻重的作用,而局域网组建方式有多种,并且各种组建方式中,网络设备配置技术也会有差别。局域网常见的组网方式有共享网络、交换网络、路由网络。路由网络这种组网方式能解决网络分隔管理、抑制广播风暴,在局域网的组网方式当中具有代表性。阐述了计算机网络的组网及设备配置,并利用三层交换机和VLAN技术,分析了对局域网中广播风暴进行控制,使频繁数据交换的局域网能从容交换数据。     

An Approach to Correctness of Data Parallel Algorithms

The design of data parallel algorithms for fine-grain machines is a fundamental domain in today′s computer science. High standards in the specification and resolution of problems have been achieved in the sequential case. It seems reasonable to apply the same level of quality to data parallel programs. It appears that most data parallel problems can be specified in terms of pre- and postconditions. These conditions characterize the overall state of the fine-grain processors in the initial and final states. In this paper:

• •We present an axiomatic system to prove correctness of data parallel algorithms on single-instruction multiple-data (SIMD) machines.
• •We specify some data parallel problems like tree sum, root finding, radix sorting, and dynamic memory allocation.
• •With this set of axioms we prove the correctness of programs solving the problems above.

It seems that the framework for data parallel problems is quite different from those for problems of parallelism with multiple threads of control, like those solvable in Communicating Sequential Processes (CSP).     

容错的网络声明式程序

介绍了基于递归规则的网络声明式语言Netlog的语法和分布式不动点语义,定义了强良好的程序,并证明了强良好的程序的计算结果对有限的消息丢失不敏感.     

高校网络技术课程网络设备配置教学方案

目前在网络课程教学过程中,网络设备配置内容学习或偏重理论,或片面强调动手实践,造成网络学习者独立解决问题能力、实际配置网络能力和操作水平达不到应用要求。本文结合社会紧缺的创新型、复合型网络人才需求,提出一套切实可行,既能深化理论又能提高实训的优质教学方案,为下一步实践教学改革提供可行的模式参考依据,为培养具有网络配置能力、管理能力的网络技术人才打下坚实基础。     

PLC程控配置方案探讨

随着主体设备可控性及控制元件可靠性的提高,火电厂辅助车间的控制系统自动化水平也越来越得到重视。重点对采用可编程序控制器（PLC）来实现火电厂辅助系统的程序控制配置方案进行了探讨。     

一种设计分解的正确性证明

二维变量化设计系统可以用含有n个未知数、m个方程的非线性方程组表示．通过设计分解可以提高几何约束求解的效率和数值稳定性．给出了一种基于图论的设计分解方法及其正确性证明．该方法可以（1）处理结构欠约束系统的分解;（2）检测出冗余约束．分解算法在有限步内终止,其结果是结构相容的     

Configuration for Adaptation – A Human-centered Approach to Flexible Workflow Enactment

The advantages of today's processmanagement, such as efficiency and quality aspects,are achieved by enforcing detailed models of workprocesses. However, real world processes can beplanned to a limited degree only and sometimes plannedparts of the process must be changed,creating a need for additional, unforeseen activities.This paper suggests an approach that configuresparts of a detailed process model with differentsupport strategies. The explicit modelling of thesesupport strategies allows them to be changed ifdemanded by the situation. When enacting such aprocess model it is then possible to vary the degreeto which the model determines the work ofindividuals. The concept is based on an earlierenactment concept which allowed workers to freelychoose methods for their tasks according to thesituation. Besides the incorporation of differentsupport strategies, the extended enactment strategygives workers the opportunity to negotiate aboutchanging a currently too restrictive support strategy,giving scope for deviations from the plannedprocess where additional actions are required.     

A Component-Based Debugging Approach for Detecting Structural Inconsistencies in Declarative Equation Based Models

Object-oriented modeling with declarative equation based languages often unconsciously leads to structural inconsistencies. Component-based debugging is a new structural analysis approach that addresses this problem by analyzing the structure of each component in a model to separately locate faulty components. The analysis procedure is performed recursively based on the depth-first rule. It first generates fictitious equations for a component to establish a debugging environment, and then detects structural defects by using graph theoretical approaches to analyzing the structure of the system of equations resulting from the component. The proposed method can automatically locate components that cause the structural inconsistencies, and show the user detailed error messages. This information can be a great help in finding and localizing structural inconsistencies, and in some cases pinpoints them immediately.     

A Bayesian Network Approach to Program Generation

Genetic programming (GP) is a powerful optimization algorithm that has been applied to a variety of problems. This algorithm can, however, suffer from problems arising from the fact that a crossover, which is a main genetic operator in GP, randomly selects crossover points, and so building blocks may be destroyed by the action of this operator. In recent years, evolutionary algorithms based on probabilistic techniques have been proposed in order to overcome this problem. In the present study, we propose a new program evolution algorithm employing a Bayesian network for generating new individuals. It employs a special chromosome called the expanded parse tree, which significantly reduces the size of the conditional probability table (CPT). Prior prototype tree-based approaches have been faced with the problem of huge CPTs, which not only require significant memory resources, but also many samples in order to construct the Bayesian network. By applying the present approach to three distinct computational experiments, the effectiveness of this new approach for dealing with deceptive problems is demonstrated.      

A Lagrangean Approach to Network Design Problems

Network design is a very important issue in the area of telecommunications and computer networks, where there is a large need for construction of new networks. This is due to technological development (fiber optics for telecommunication) and new ways of usage (Internet for computer networks). Optimal design of such networks requires formulation and solution of new optimization models. In this paper, we formulate several fixed charge network design models, capacitated or uncapacitated, directed or undirected, possibly with staircase costs, and survivability requirements. We propose a common solution approach for all these problems, based on Lagrangean relaxation, subgradient optimization and primal heuristics, which together form a Lagrangean heuristic. The Lagrangean heuristic can be incorporated into a branch-and-bound framework, if the exact optimal solution must be found. The approach has been tested on problems of various structures and sizes, and computational results are presented.     

基于攻防策略的网络设备安全与协同配置

在网络安全领域,以互联为主的网络设备是基础,以安全防护为主的防火墙与入侵检测等安全组件是核心。重点对常用网络设备的原理与安全配置进行探讨,在此基础上,提出了针对各种网络攻击的网络设备的安全与协同配置策略,以建立高可靠性的网络安全环境。     

基于攻防策略的网络设备安全与协同配置

在网络安全领域，以互联为主的网络设备是基础，以安全防护为主的防火墙与入侵检测等安全组件是核心。重点对常用网络设备的原理与安全配置进行探讨，在此基础上，提出了针对各种网络攻击的网络设备的安全与协同配置策略，以建立高可靠性的网络安全环境。     

Study on Cache Configuration of A Muitithreaded Approach

By exploiting both Instruction Level Parallelism （ILP） and Thread Level Parallelism （TLP）, the simultaneous multithread architecture can be expected to achieve better tradeoff between performance and hardware cost. This paper studies the impact to performance on different cache configurations quantitatively on the same benchmarks. It can help to find the exploitability of this architecture to different application area,     

A New Approach to Multivariate Network Traffic Analysis

Journal of Computer Science and Technology - Network traffic analysis is one of the core functions in network monitoring for effective network operations and management. While online traffic...     

A Neural Network Approach to Tracking Eye Position

The design of a neural network based eye tracker is presented. A series of experiments with counterpropagation neural networks convert synthetic video images into eye coordinates by an enhanced feed-forward neural network with multiple winning hidden layer nodes. Difficulties encountered during the design process are discussed. The results show that accurate, fine-grained tracking of a human's eye position is possible by processing the video image collected from a goggle-mounted miniature charge-coupled device (CCD) camera.     

Object-Oriented Data Modelling for Graphics Databases: a Declarative Approach

This paper presents a new scheme to integrate the declarative approach to graphics and object-oriented data modelling techniques to form a fruitful symbiosis for constraint-based graphics database systems. It has rich modelling constructs to describe graphics data and allows sharing of representation. It also provides useful mechanisms for management of integrity constraints. We have also identified important classes of constraints in the context of object-oriented graphics database systems. Examples are given for maintenance of constraints at the time of insertion, deletion and modification.     

PROFIBUS网络配置方案

本文介绍了PROFIBUS网络技术,并针对不同的现场条件及用户要求提出了不同的网络配置方案。同时给出了网络配置过程中应注意到的几个关键技术问题。