基于政策自组织系统的软件agent体系结构及其实现

当前自组织系统软件工程面临的一个重要挑战,就是如何设计适宜的个体交互行为来满足自组织系统的宏观涌现需求。针对此问题,提出了一种基于政策的自组织多agent系统的开发方法,此方法通过政策调节引导agent的行为,以期在系统层面得到用户所需求的宏观涌现结果。开发这类系统的核心问题是如何构造系统中的软件agent,使得agent能够感知、理解系统政策,并在遵循政策的前提下实现行为的自主决策。提出了一种基于政策自组织多agent系统的软件agent体系结构,并基于该体系结构设计了运行机制及行为决策算法。通过软件方式实现了一个基于政策的自组织多agent系统开发平台原型,并通过案例实现说明了体系结构、运行机制的有效性。     

Prototype of fault adaptive embedded software for large-scale real-time systems

This paper describes a comprehensive prototype of large-scale fault adaptive embedded software developed for the proposed Fermilab BTeV high energy physics experiment. Lightweight self-optimizing agents embedded within Level 1 of the prototype are responsible for proactive and reactive monitoring and mitigation based on specified layers of competence. The agents are self-protecting, detecting cascading failures using a distributed approach. Adaptive, reconfigurable, and mobile objects for reliablility are designed to be self-configuring to adapt automatically to dynamically changing environments. These objects provide a self-healing layer with the ability to discover, diagnose, and react to discontinuities in real-time processing. A generic modeling environment was developed to facilitate design and implementation of hardware resource specifications, application data flow, and failure mitigation strategies. Level 1 of the planned BTeV trigger system alone will consist of 2500 DSPs, so the number of components and intractable fault scenarios involved make it impossible to design an ‘expert system’ that applies traditional centralized mitigative strategies based on rules capturing every possible system state. Instead, a distributed reactive approach is implemented using the tools and methodologies developed by the Real-Time Embedded Systems group.     

Compositional design of isochronous systems

The synchronous modeling paradigm provides strong correctness guarantees for embedded system design while requiring minimal environmental assumptions. In most related frameworks, global execution correctness is achieved by ensuring the insensitivity of (logical) time in the program from (real) time in the environment. This property, called endochrony or patience, can be statically checked, making it fast to ensure design correctness. Unfortunately, it is not preserved by composition, which makes it difficult to exploit with component-based design concepts in mind. Compositionality can be achieved by weakening this objective, but at the cost of an exhaustive state-space exploration. This raises a trade-off between performance and precision. Our aim is to balance it by proposing a formal design methodology that adheres to a weakened global design objective: the non-blocking composition of weakly endochronous processes, while preserving local design objectives for synchronous modules. This yields an effective and cost-efficient approach to compositional synchronous modeling.     

Development,implementation, and experimental outdoor evaluation of quadcopter controllers for computationally limited embedded systems

Quadcopters are increasingly used for applications ranging from hobby to industrial products and services. This paper serves as a tutorial on the design, simulation, implementation, and experimental outdoor testing of digital quadcopter flight controllers, including Explicit Model Predictive Control, Linear Quadratic Regulator, and Proportional Integral Derivative. A quadcopter was flown in an outdoor testing facility and made to track an inclined, circular path at different tangential velocities under ambient wind conditions. Controller performance was evaluated via multiple metrics, such as position tracking error, velocity tracking error, and onboard computation time. Challenges related to the use of computationally limited embedded hardware and flight in an outdoor environment are addressed with proposed solutions.     

Pipelines on heterogeneous systems: models and tools

We study the performance of pipeline algorithms in heterogeneous networks. The concept of heterogeneity is not only restricted to the differences in computational power of the nodes, but also refers to the network capabilities. We develop a skeleton tool that allows us an efficient block‐cyclic mapping of pipelines on heterogeneous systems. The tool supports pipelines with a number of stages much larger than the number of physical processors available. We derive an analytical formula that allows us to predict the performance of pipelines in heterogeneous systems. According to the analytical complexity formula, numerical strategies to solve the optimal mapping problem are proposed. The computational results prove the accuracy of the predictions and effectiveness of the approach. Copyright © 2005 John Wiley & Sons, Ltd.     

Soft systems and systems engineering: on the use of conceptual models in information system development

Abstract. Many recent studies have shown that computer-based systems continue to ‘fail’ at a number of different levels (Romtec, 1988; KPMG, 1990) and it is increasingly apparent (Maclaren et al., 1991) that the most serious failures of information technology (IT) lie in the continuing inability to address those concerns which are central to the successful achievement of individual, organizational and social goals. It is the contention of this paper that this failing is precisely because these are the areas which are ignored or inadequately treated by conventional system development methods. There is, of course, a vast body of literature concerned with the understanding of complex human activity systems. This literature often reflects a mass of contradictions at the epistemological and the ontological level about the behaviour of such systems and has also spawned numerous methods (and methodologies) which seek to guide the individual in making successful interventions into organizational situations (Rosenhead, 1989). Despite this multiplicity of viewpoints many writers have posited a dichotomy between so-called 'soft and ‘hard’ approaches to problem situations and use this dichotomy to inform the choice of an appropriate problem-solving methodology (Checkland, 1985). In this paper we characterize these two approaches as being concerned with either the purpose(s) of the human activity system (i.e. ‘doing the right thing’) or with the design of the efficient means of achieving such purpose(s) (i.e. ‘doing the thing right’). It is our belief that much of the literature and work in either area has not concerned itself with the issues of the other. Writers on ‘hard’ engineering methods often assume the question of purpose to be either straightforward (e.g. given in the project brief) or, paradoxically, too difficult (e.g. it is not our concern as mere systems analysts). Writers on ‘soft’ methods on the other hand rarely have anything to say about the design and implementation of well-engineered computer-based systems, giving the impression that this is a somewhat mundane activity better left to technical experts. This paper, therefore, attempts to set out a rationale for the bringing together of principles from both ‘hard’ engineering and ‘soft’ inquiry methods without doing epistemological damage to either. To illustrate our argument we concentrate on JSD (Jackson system development) as an example of system engineering (Cameron, 1983) and SSM (soft systems methodology) as an example of system inquiry (Checkland, 1981; Checkland & Scholes, 1990). Our general thesis, however, does not depend upon either of these two approaches per se but applies to the overall issue of bringing together insights from two apparently opposed epistemological positions in an effort better to harness the power of IT in pursuit of purposeful human activity.     

Examining virtual reality as a platform for developing mental models of industrial systems

Industrial systems can be complex and not intuitive to perceive. Therefore, students in technology and engineering programs can benefit from developing mental models of industrial systems during their journey in college. However, more often than not, these students do not have access to industrial facilities; thus, developing mental models for systems is a challenge. This paper examines the merit of an Immersive Virtual Reality (IVR) framework application in creating proper mental models for industrial systems in technology and engineering students. Two IVR applications were developed. One IVR application afforded interaction with components of a prefabricated industrial cooling water system (CWVR). In the other application, students designed and built industrial systems with IVR (system designer VR [SDVR]). SDVR facilitated constructive-generative engagement. A group of 33 students was divided into two; one group (the Design, experimental group) was tasked with building a system with SDVR and interacting with the cooling water system in CWVR. The other group was tasked with directly interacting with the CWVR without building a system with SDVR (the Interaction, comparison group). Students' mental models of the cooling water system in CWVR were evaluated following completing the interaction experience with CWVR. The results demonstrate that the causal model notion of the mental model of the cooling water system was significantly higher in the Design, experimental group. The results suggest that designing a rich IVR application that facilitates constructive-generative engagements may carry merit in informing student mental models of complex technical concepts.     

Dialectical hermeneutics: a theoretical framework for the implementation of information systems

Abstract. Despite the proliferation of information technology, the implementation of information systems remains problematic. Many systems fail to live up to expectations and some end up as disasters. Research on implementation has been conducted for the past two decades, but no theoretical framework for IS implementation has been widely accepted. This paper proposes dialectical hermeneutics as a theoretical framework for IS implementation research. Dialectical hermeneutics, as an integrative theoretical framework, combines both interpretive and critical elements, and addresses those social and organizational issues which are critical to the successful implementation of information systems. The case study research method was used to examine the implementation of systems in three organizations.     

Study impact of various load models on DG placement and sizing using backtracking search algorithm

In this article, a meta-heuristic technique based on a backtracking search algorithm (BSA) is employed to produce solutions to ascertain distributed generators (DGs). The objective is established to reduce power loss and improve network voltage profile in radial distribution networks by determining optimal locations and sizes of the DGs. Power loss indices and bus voltages are engaged to explore the initial placement of DG installations. The study cares with the DG type injects active and reactive power. The proposed methodology takes into consideration four load models, and their impacts are addressed. The proposed BSA-based methodology is verified on two different test networks with different load models and the simulation results are compared to those reported in the recent literature. The study finds that the constant power load model among various load models is sufficed and viable to allocate DGs for network loss and voltage studies. The simulation results reveal the efficacy and robustness of the BSA in finding the optimal solution of DGs allocation.     

Performance evaluation of a multithreaded RTS using a synchronous reactive model

Synchronous reactive modelling provides an optimal framework for the modular decomposition of programs that engage in complex patterns of deterministic interaction, such as many real-time and communication entities. This paper presents an approach which includes performance modelling techniques in the synchronous reactive modelling method supported by ESTEREL. It defines a methodology based on timing and probabilistic quantitative constructs that complete the synchronous reactive models. A monitoring mechanism allows the computation of performance results during the simulation. This methodology is applied to study a multithreaded runtime system for a distributed functional programming language. Performance metrics are computed and validated with experimental results.     

The use of domination and legitimation in information systems implementation

In this paper, we present the results of a longitudinal case study on information systems (IS) implementation conducted in a community healthcare organization. Using structuration theory as a sensitizing framework, we highlight how the information technology (IT) Management improved their influence through gaining legitimation from other organizational stakeholders, and how the nature of this evolved over time. Our results highlight how an appropriate, sophisticated use of what Giddens refers to as the duality of structure contributed to the consolidation of the IT Manager's credibility and authority. We also report on how the IT Management had most of their actions legitimated as an integral element of their actions. The results also highlight the distributed nature of power, such that even those at the lower end of organizational hierarchy were able to influence the success or failure of IS implementation.     

A Theory of Constraints approach to interorganizational systems implementation

Interorganizational systems (IOS) may provide substantial benefits, however many organizations are reluctant to implement them. This empirical research takes a novel approach and develops a model of IOS feasibility, which is based on the Theory of Constraints (TOC). It introduces the notion of maximal infeasibility, which is the highest among the values of five factors: economic infeasibility, organizational infeasibility, technological infeasibility, risks, and lack of financial resources. The highest value was selected because implementation is hindered even if only one of the feasibility requirements is not fulfilled. Data collected from 139 medium and large Israeli business organizations validated the model, and indicated that strategic motivation is the main driving force for an organization to initiate or to join an IOS, while the main barriers are organizational infeasibility issues such as lack of management support or uninterested potential partners. Adopting a TOC approach to IOS implementation may assist organizations to overcome these obstacles and increase the chance of a successful implementation. An earlier shorter version of this paper was presented at WEB 2006, a pre-ICIS workshop on e-business, in Milwaukee, WI.     

Verifying distributed real-time properties of embedded systems via graph transformations and model checking

Component middleware provides dependable and efficient platforms that support key functional, and quality of service (QoS) needs of distributed real-time embedded (DRE) systems. Component middleware, however, also introduces challenges for DRE system developers, such as evaluating the predictability of DRE system behavior, and choosing the right design alternatives before committing to a specific platform or platform configuration. Model-based technologies help address these issues by enabling design-time analysis, and providing the means to automate the development, deployment, configuration, and integration of component-based DRE systems. To this end, this paper applies model checking techniques to DRE design models using model transformations to verify key QoS properties of component-based DRE systems developed using Real-time CORBA. We introduce a formal semantic domain for a general class of DRE systems that enables the verification of distributed non-preemptive real-time scheduling. Our results show that model-based techniques enable design-time analysis of timed properties and can be applied to effectively predict, simulate, and verify the event-driven behavior of component-based DRE systems. This research was supported by the NSF Grants CCR-0225610 and ACI-0204028 Gabor Madl is a Ph.D. student and a graduate student researcher at the Center for Embedded Computer Systems at the University of California, Irvine. His advisor is Nikil Dutt. His research interests include the formal verification, optimization, component-based composition, and QoS management of distributed real-time embedded systems. He received his M.S. in computer science from Vanderbilt University and in computer engineering from the Budapest University of Technology and Economics. Dr. Sherif Abdelwahed received his Ph.D. degree in Electrical and Computer Engineering from the University of Toronto, Canada, in 2001. During 2000–2001, he was a research scientist with the system diagnosis group at the Rockwell Scientific Company. Since 2001 he has been with the Department of Electrical Engineering and Computer Science at Vanderbilt University as a Research Assistant Professor. His research interests include verification and control of distributed real-time systems, and model-based diagnosis of discrete-event and hybrid systems. Dr. Douglas C. Schmidt is a Professor of Computer Science, Associate Chair of the Computer Science and Engineering program, and a Senior Researcher in the Institute for Software Integrated Systems (ISIS) all at Vanderbilt University. He has published over 300 technical papers and 6 books that cover a range of research topics, including patterns, optimization techniques, and empirical analyses of software frameworks and domain-specific modeling environments that facilitate the development of distributed real-time and embedded (DRE) middleware and applications. Dr. Schmidt has served as a Deputy Office Director and a Program Manager at DARPA, where he lead the national R&D effort on middleware for DRE systems. In addition to his academic research and government service, Dr. Schmidt has over fifteen years of experience leading the development of ACE, TAO, CIAO, and CoSMIC, which are widely used, open-source DRE middleware frameworks and model-driven tools that contain a rich set of components and domain-specific languages that implement patterns and product-line architectures for high-performance DRE systems.     

Wiener models of direction-dependent dynamic systems

Analysis of systems with direction-dependent dynamics is currently limited to cases in which the dynamics in the two directions of the output are first order; results for such systems have been published for both pseudo-random maximum-length binary (MLB) and inverse-repeat maximum-length binary (IR-MLB) inputs. These relatively limited analytical results make it useful to examine alternative ways of modelling such systems and in this paper, Wiener models are considered for this purpose. Methods for optimising the Wiener model parameters by matching the system and model cross-correlation functions, outputs, and discrete Fourier transforms of the outputs are considered, and the results are compared. These methods are also applied to a first-order direction-dependent system with a maximum-length ternary (MLT) input, for which no analytical results are currently available, and to a second-order system with an IR-MLB input.     

嵌入式PC为节点的分布式监控系统的实现

描述了一个以嵌入式PC为控制节点的分布式监控系统,系统基于现场总线连接,用Modem实现通信,节点用嵌入式PC实现。给出了系统结构,分析了节点工作原理及接口电路,并讨论了软件开发。     

基于OGC规范的多星多传感器卫星地面系统设计与实现

为解决传统卫星地面系统各业务功能单一、异构组织协作方面的不足, 提出了新型卫星地面系统的设计架构。以OGC(Open Geospatial Consortium)组织制定的空间信息服务标准为核心, 分别研究了卫星地面系统各业务系统的服务化, 给出了完整的新型卫星地面系统框架体系, 并进行了原型系统的开发和相关的应用实验。结果表明, 新型的卫星地面系统有助于实现多星多传感器的动态添加和跨组织协调合作。     

Evaluation of stereo correspondence algorithms and their implementation on FPGA

The accuracy of stereo vision has been considerably improved in the last decade, but real-time stereo matching is still a challenge for embedded systems where the limited resources do not permit fast operation of sophisticated approaches. This work presents an evaluation of area-based algorithms used for calculating distance in stereoscopic vision systems, their hardware architectures for implementation on FPGA and the cost of their accuracies in terms of FPGA hardware resources. The results show the trade-off between the quality of such maps and the hardware resources which each solution demands, so they serve as a guide for implementing stereo correspondence algorithms in real-time processing systems.     

The impact of EDI implementation commitment and implementation success on competitive advantage and firm performance

Abstract. Electronic Data Interchange Systems (EDI) are increasingly being used by business firms to improve operations and customer service. One of the major motivations for business organizations using EDI is to gain a strategic advantage in the marketplace. Although EDI has been implemented by many organizations, unfortunately not all have gained the same level of expected advantage or envisioned benefits.
In this study we focus on the impact of EDI implementation commitment and implementation success on competitive advantage and firm performance. We study two categories of companies: companies that initiate the development of EDI and are known as hub companies and those that are their non-hub counterparts. Findings indicate that non-hub firms may not reap the same level of expected benefits resulting from EDI technology adoption and implementation as hub firms.