一种面向软件体系结构的动态重配置方法*

通过在整个软件生命周期建立开发模型,研究了当前软件工程与实际需求之间差异。利用基于XML的中间脚本,提出一种事务处理软件开发模型,实现用户功能需求到表单流、事件流和数据流的转换,动态重配置出不同应用的事务处理软件。建立了企事业信息综合事务处理系统开发平台,分析了平台体系结构和中间脚本,表明可以根据业务变化进行整个系统功能重组而不需要编写一句程序,验证了该模型的可行性和有效性。     

Genetic algorithm-based dynamic reconfiguration for networked control system

This paper represents a genetic algorithm (GA) based dynamic reconfiguration for networked control systems (NCS) with the objective of minimizing network time-delay. With the development of NCS, it is become more and more important for them to have the minimum time-delay and the ability of dynamic reconfiguration, which can accommodate the changes rapidly, smartly and flexibly. And it is important to find a routing algorithm, which is quicker to reduce the time to update the router and decrease the reconfiguration time as much as possible. In this paper, based on NCS, we discuss the process of GA with specialized encoding, initialization, selection, crossover and mutation. A specialized repair function is used to improve performance. In addition, experiment results are given to illuminate that GA can improve the performance of the NCS. This work was supported by grants from the National Natural Science Foundation of China (No.60674081 and No.60574088).     

构件间依赖关系的形式化图形原语描述方法

目前,基于构件的软件系统的研究越来越引起人们的重视.提出了一种基于图形的构件间依赖关系的描述方法,并对CORBA分布式应用中构件间依赖关系的描述和依赖关系的动态更新进行了较详细的分析.在CORBA上实现了一个原型,从而实现了基于CORBA的分布式应用的动态配置.     

A fault tolerant NoC architecture using quad-spare mesh topology and dynamic reconfiguration

Network-on-Chip (NoC) is widely used as a communication scheme in modern many-core systems. To guarantee the reliability of communication, effective fault tolerant techniques are critical for an NoC. In this paper, a novel fault tolerant architecture employing redundant routers is proposed to maintain the functionality of a network in the presence of failures. This architecture consists of a mesh of 2 × 2 router blocks with a spare router placed in the center of each block. This spare router provides a viable alternative when a router fails in a block. The proposed fault-tolerant architecture is therefore referred to as a quad-spare mesh. The quad-spare mesh can be dynamically reconfigured by changing control signals without altering the underlying topology. This dynamic reconfiguration and its corresponding routing algorithm are demonstrated in detail. Since the topology after reconfiguration is consistent with the original error-free 2D mesh, the proposed design is transparent to operating systems and application software. Experimental results show that the proposed design achieves significant improvements on reliability compared with those reported in the literature. Comparing the error-free system with a single router failure case, the throughput only decreases by 5.19% and latency increases by 2.40%, with about 45.9% hardware redundancy.     

基于场景分析的系统形式化模型生成方法

采用形式化方法对系统的安全性进行分析与验证,是构造可靠安全软件系统的一个重要途径。当前的形式化安全分析方法,面临着系统的形式化建模难的问题。以铁路车站联锁系统中基本进路建立为例,提出基于场景分析的系统形式化模型生成方法。该方法首先采用OCL前/后置条件分析法对UML时序场景作一致性分析,然后将UML时序图中对象交互的行为序列转换成FSP进程代数模型,进而得到系统的形式化模型。该方法为系统的形式化建模提供了新思路,从安全质量方面改善了安全苛求软件的设计与开发,丰厚了基于模型的软件形式化开发方法。     

Evaluating the impacts of dynamic reconfiguration on the QoS of running systems

A major challenge in dynamic reconfiguration of a running system is to understand in advance the impact on the system's Quality of Service (QoS). For some systems, any unexpected change to QoS is unacceptable. In others, the possibility of dissatisfaction increases due to the impaired performance of the running system or unpredictable errors in the resulting system. In general it is difficult to choose a reasonable reconfiguration approach to satisfy a particular domain application. Our investigation on this issue for dynamic approaches is four-fold. First, we define a set of QoS characteristics to identify the evaluation criteria. Second, we design a set of abstract reconfiguration strategies bringing existing and new approaches into a unified evaluation context. Third, we design a reconfiguration benchmark to expose a rich set of QoS problems. Finally, we test the reconfiguration strategies against the benchmark and evaluate the test results. The analysis of acquired results helps to understand dynamic reconfiguration approaches in terms of their impact on the QoS of running systems and possible enhancements for newer QoS capability.     

Detecting faults in heterogeneous and dynamic systems using DSP and an agent-based architecture

This paper demonstrates the use of multi-agent systems (MAS), firstly as a modelling technique for dynamic physical systems and secondly as the basis for a generic and powerful diagnostic system, which can support heterogeneous distributed systems. First an overview of the diagnostic techniques including those offered by the two communities fault detection and isolation (FDI ) and DX (based on intelligent techniques) is given. The use of digital signal processing (DSP) as a significant technique for improved fault diagnosis is illustrated. A rule-based engine is used to control the behaviours of the agents and also as a tool for diagnosis. Finally, the integration of DSP agents and the rule-based engine into MAS is demonstrated using a real-life application, a class-AB amplifier (a power electronic circuit). It is shown that the integration of DSP agents and rules into MAS provides a powerful tool for prognosis and for detection of abrupt (short and open circuit) and incipient faults.     

FPGA远程动态重构技术的研究

提出了一种FPGA远程动态重构的方法,结合FPGA动态重构技术和GSM通信技术来实现。利用GSM技术实现配置数据的无线传输,在单片机控制下将数据存储于CF卡中。在内嵌硬核微处理器PowerPC405控制下,FPGA通过内部配置存取端口读取CF卡中新的配置数据,对可重构区进行配置以实现新的功能。     

Formulation and analysis of dynamic supply chain of backfill in construction waste management using agent-based modeling

Backfill is the excavated material from earthworks, which constitutes over 50% of the construction wastes in Hong Kong. This paper considers a supply chain that consists of construction sites, landfills and commercial sources in which operators seek cooperation to maximize backfill reuse and improve waste recovery efficiency. Unlike the ordinary material supply chain in manufacturing industries, the supply chain for backfill involves many dynamic processes, which increases the complexity of analyzing and solving the logistic issue. Therefore, this study attempts to identify an appropriate methodology to analyze the dynamic supply chain, for facilitating the backfill reuse. A centralized optimization model and a distributed agent-based model are proposed and implemented in comparing their performances. The centralized optimization model can obtain a global optimum but requires sharing of complete information from all supply chain entities, resulting in barriers for implementation. In addition, whenever the backfill supply chain changes, the centralized optimization model needs to reconfigure the network structure and recompute the optimum. The distributed agent-based model focuses on task distribution and cooperation between business entities in the backfill supply chain. In the agent-based model, decision making and communication between construction sites, landfills, and commercial sources are emulated by a number of autonomous agents. They perform together through a negotiation algorithm for optimizing the supply chain configuration that reduces the backfill shipment cost. A comparative study indicates that the agent-based model is more capable of studying the dynamic backfill supply chain due to its decentralization of optimization and fast reaction to unexpected disturbances.     

Configuration and dynamic reconfiguration of components using the coordination paradigm

One of the most promising approaches in developing component-based (possibly distributed) systems is that of coordination models and languages. Coordination programming enjoys a number of advantages such as the ability to express different software architectures and abstract interaction protocols, support for multi-linguality, reusability and programming-in-the-large, etc. Configuration programming is another promising approach in developing large scale, component-based systems, with the increasing need for supporting the dynamic evolution of components. In this paper we explore and exploit the relationship between the notions of coordination and (dynamic) configuration and we illustrate the potential of control- or event-driven coordination languages to be used as languages for expressing dynamically reconfigurable software architectures. We argue that control-driven coordination has similar goals and aims with the notion of dynamic configuration and we illustrate how the former can achieve the functionality required by the latter.     

Side-channel countermeasures utilizing dynamic logic reconfiguration: Protecting AES/Rijndael and Serpent encryption in hardware

Dynamic logic reconfiguration is a concept that allows for efficient on-the-fly modifications of combinational circuit behavior in both ASIC and FPGA devices. The reconfiguration of Boolean functions is achieved by modification of their generators (e.g., shift register-based look-up tables) and it can be controlled from within the chip, without the necessity of any external intervention. This hardware polymorphism can be utilized for the implementation of side-channel attack countermeasures, as demonstrated by Sasdrich et al. for the lightweight cipher PRESENT.In this work, we adapt these countermeasures to two of the AES finalists, namely Rijndael and Serpent. Just like PRESENT, both Rijndael and Serpent are block ciphers based on a substitution–permutation network. We describe the countermeasures and adjustments necessary to protect these ciphers using the resources available in modern Xilinx FPGAs. We describe our implementations and evaluate the side-channel leakage and effectiveness of different countermeasures combinations using a methodology based on Welch’s t-test. Furthermore, we attempt to break the protected AES/Rijndael implementation using second-order DPA/CPA attacks.We did not detect any significant first-order leakage from the fully protected versions of our implementations. Using one million power traces, we detect second-order leakage from Serpent encryption, while AES encryption second-order leakage is barely detectable. We show that the countermeasures proposed by Sasdrich et al.are, with some modifications, successfully applicable to AES and Serpent.     

A multi-formalism approach for model-based dynamic distribution of user interfaces of critical interactive systems

Evolution in the context of use requires evolutions in the user interfaces even when they are currently used by operators. User Centered Development promotes reactive answers to this kind of evolutions either by software evolutions through iterative development approaches or at runtime by providing additional information to the operators such as contextual help for instance. This paper proposes a model-based approach to support proactive management of context of use evolutions. By proactive management we mean mechanisms in place to plan and implement evolutions and adaptations of the entire user interface (including behaviour) in a generic way. The approach proposed handles both concentration and distribution of user interfaces requiring both fusion of information into a single UI or fission of information into several ones. This generic model-based approach is exemplified on a safety critical system from space domain. It presents how the new user interfaces can be generated at runtime to provide a new user interface gathering in a single place all the information required to perform the task. These user interfaces have to be generated at runtime as new procedures (i.e. sequences of operations to be executed in a semi-autonomous way) can be defined by operators at any time in order to react to adverse events and to keep the space system in operation. Such contextual, activity-related user interfaces complement the original user interfaces designed for operating the command and control system. The resulting user interface thus corresponds to a distribution of user interfaces in a focus+context way improving usability by increasing both efficiency and effectiveness.     

Continuity aspects of embedded reconfigurable computing

In embedded systems, dynamically reconfigurable computing can be partially modified at runtime without stopping the operation of the whole system. In this paper, we consider a reorganization mechanism for dynamically reconfigurable computing in embedded systems to guarantee that invariants of the design are respected. This reorganization is considered as a visual transformation of the logical configuration by the formulated rules. The invariant is recognized under the restructuring of the configuration using reconfiguration rules.     

An agent-based modeling approach applied to the spread of cholera

Cholera is an intestinal disease and is characterized by diarrhea and severe dehydration. While cholera has mainly been eliminated in regions that can provide clean water, adequate hygiene and proper sanitation; it remains a constant threat in many parts of Africa and Asia. Within this paper, we develop an agent-based model that explores the spread of cholera in the Dadaab refugee camp in Kenya. Poor sanitation and housing conditions contribute to frequent incidents of cholera outbreaks within this camp. We model the spread of cholera by explicitly representing the interaction between humans and their environment, and the spread of the epidemic using a Susceptible-Exposed-Infected-Recovered model. Results from the model show that the spread of cholera grows radially from contaminated water sources and seasonal rains can cause the emergence of cholera outbreaks. This modeling effort highlights the potential of agent-based modeling to explore the spread of cholera in a humanitarian context.     

QoS contract preservation through dynamic reconfiguration: A formal semantics approach

The increasing pervasiveness of computing services in everyday life, combined with the dynamic nature of their execution contexts, constitutes a major challenge in guaranteeing the expected quality of such services at runtime. Quality of Service (QoS) contracts have been proposed to specify expected quality levels (QoS levels) on different context conditions, with different enforcing mechanisms. In this paper we present a definition for QoS contracts as a high-level policy for governing the behavior of software systems that self-adapt at runtime in response to context changes. To realize this contract definition, we specify its formal semantics and implement it in a software framework able to execute and reconfigure software applications, in order to maintain fulfilled their associated QoS contracts. The contribution of this paper is threefold. First, we extend typed-attributed graph transformation systems and finite-state machines, and use them as denotations to specify the semantics of QoS contracts. Second, this semantics makes it possible to systematically exploit design patterns at runtime by dynamically deploying them in the managed software application. Third, our semantics guarantees self-adaptive properties such as reliability and robustness in the contract satisfaction. Finally, we evaluate the applicability of our semantics implementation by integrating and executing it in FraSCAti, a multi-scale component-based middleware, in three case studies.     

Developing an agent-based hierarchical modeling approach to assess human performance of infrastructure systems

During the last decade, research works related to modeling and simulation of infrastructure systems have primarily focused on the performance of their technical factors, almost ignoring the importance of non-technical factors of these systems, e.g., human operators, consumers. In contrast, the human operator of infrastructure systems has become an essential part in daily operation and in ensuring the security and reliability of the system. In some of the most significant technological incidents of the past century, human error has played a major role. Therefore, developing a modeling approach that is capable of assessing the human performance in a comprehensive way has become crucial. In this paper, an agent-based hierarchical modeling approach is proposed, which aims at the explicit modeling of the impacts of human performance on the operation of infrastructure systems. Within this approach, the cognition component plays a major role. For this purpose, an analytical method based on the Cognitive Reliability Error Analysis Method (CREAM) is developed using a knowledge-based approach. The proposed modeling approach is a pilot work exploring possibilities of simulating performance of human factors in infrastructure systems. The applicability of this modeling approach is demonstrated by a validation experiment using the electric power supply system as an exemplary system.     

Formal methods software engineering for the CARA system

This paper discusses the application of formal methods software engineering (FMSE) to the development of the Computer Automated Resuscitation A (CARA) medical device at Walter Reed Army Institute of Research. Because this system is potentially life critical, a high level of quality was required. A formal engineering approach to the software development activities was chosen to satisfy this need. Specifically, a technique called sequence enumeration was applied to elicit and refine requirements while deriving a formal specification. The fundamentals of the specification process that was used on the project are described along with a brief summary of the project experience in the development and testing phases. The project employed recent advances in Cleanroom software engineering methods along with older box-structured development and usage-model-based statistical testing techniques.     

Experimenting with dynamic linking with ADA

An approach to achieving dynamic reconfiguration within the framework of Ada¹ is described. A technique for introducing a kernel facility for dynamic reconfiguration in Ada is illustrated, and its implementation using the Verdix VADS 5.5 Ada compiling system on a Sun3–120 running the 4.3 BSD Unix operating system is discussed. This experimental kernel allows an Ada program to change its own configuration dynamically, linking new pieces of code at run-time. It is shown how this dynamic facility can be integrated consistently at the Ada language level, without introducing severe inconsistencies with respect to the Standard semantics.     

浅析网络重构方法提高配电系统可靠性

本文提出一种通过网络优化重构来提高配电系统可靠性的概念,建立了以可靠性指标最优为目标函数的数学模型。根据配电网络的特点,首次将Tabu搜索方法应用于网络重构的寻优。结果表明,Tabu搜索方法非常适合于求解配网重构问题,配网重构也能有效提高系统可靠性。