基于Petri Nets的协调机制研究*

利用形式化和图形化的建模工具Petri Nets对协调问题中的依赖关系及协调机制进行研究;提出任务之间基于资源的三种基本依赖关系;并用Petri Nets对这三种依赖关系相应的协调机制进行了表述,为协调问题的可计算描述提供了一种新的思考角度。     

AN ONTOLOGY FOR COORDINATION

Independent agents that interact within open, distributed, and decentralized environments need to collaboratively regulate their activities in order to facilitate the harmonious and successful achievement of possibly conflicting tasks. Coordination is the process of managing these interactions by identifying and possibly resolving the interdependencies occurring between such activities. A successful coordination mechanism facilitates mutually beneficial interdependencies (e.g., by ensuring activities are not duplicated) while avoiding adverse outcomes (e.g., by preventing two processes simultaneously accessing the same non-shareable resource, potentially causing deadlock). However, for such a mechanism to work effectively within open systems, agents need to communicate and reason about activities, resources, and their properties; i.e., to commit to a shared ontology of coordination that defines the semantics underlying the different coordination regimes. This article describes an ontological approach to coordination in which agents dynamically manage the interdependencies that arise during their interactions. A proof-of-concept implementation in the insurance domain is described and empirically evaluated.     

Dynamic State Charts: composition and coordination of complex robot behavior and reuse of action plots

Support for separation of roles is decisive towards a successful business ecosystem where various stakeholders with dedicated expertises network and collaborate. However, it depends on means for composition(system of systems, reuse of black boxes). This paper proposes Dynamic State Charts as an extension of state charts for composition and coordination of complex robot behavior which is one of the challenges in service robotics. Their states allow to refine their content by choosing from a set of alternative matching state instances for robust task execution and to manage the complexity of real-world tasks. Dynamic State Charts allow reuse and can be bundled with software components and are provided in a repository (idea of an “robot app store”) as a step towards composition and separation of roles as necessary for a business ecosystem in service robotics. The approach is demonstrated in a practical application with a service robot.     

Cooperation coordination in virtual enterprises

Coordination of activities is a determinant element in virtual enterprises. Proper coordination policies supported by flexible coordination mechanisms are necessary to ensure the cooperation among partner enterprises. This paper presents the PRODNET approach to support coordination in virtual enterprises. The adopted model considers on flexibility and configurability as the key aspects to cope with the large diversity of expectable scenarios and operating policies in the virtual enterprise environment. A workflow based approach for coordination is described and especial emphasis is put on a multi-level coordination view. The developed software modules that support the coordination mechanisms are presented, and finally some directions for further research are given.     

Understanding the functions of teleconferences for coordinating global software development projects

One of the dominant characteristics of contemporary software development is the global distribution of tasks, of developers, of information and of technologies. Undoubtedly, such distribution engenders new coordination challenges in the form of distance‐related interdependencies. One of the predominant processes of addressing these challenges is electronic meetings (or teleconferences). However, the functions of these meetings for coordination purposes are not yet understood. The distinctive conventions of teleconferences and their causal relationships that lead to optimal coordination of global software development (GSD) projects are also not yet understood. In this paper, the functions of teleconferences held by globally distributed software developers to coordinate their work in the face of global distribution of resources, cross‐site information interdependencies and continuously changing software requirements are analysed. The analysis is based on a qualitative study of how a subunit of 13 software developers, distributed across three sites in the USA and one in Republic of Ireland, used teleconferences to address its coordination challenges. The paper proffers a teleconference approach to GSD coordination by arguing that the functions of teleconferences manifest in software developers' multitasking; their ready access to all their information as additional benefits; flexibility in their communicative behaviours; and a reduction in their structure overload. This approach draws attention to these manifestations as distinctive conventions of the de‐structured meeting, which de‐structuring is occasioned by organic information processing needs in teleconferencing. This approach also explains why the combination of global distribution and teleconferences is a strategic opportunity for information processing for software process coordination.     

A distributed problem-solving approach to collaborative facility engineering

A framework for collaborative facility engineering is presented. The framework is based on a distributed problem-solving approach to collaborative facility engineering and employs an integration approach called Agent-Based Software Engineering as an implementation vehicle of this approach. The focal entity of this framework is a Multiagent Design Team (MDT) that comprises a collection of software agents (e.g. design software applications with a certain standard communication interface) and a design specialist, which together perform specific design tasks. Multiagent design teams are autonomous and form an organizational structure based on a federation architecture. Every multiagent design team surrenders its autonomy to a system program called facilitator, which coordinates the interaction among software agents in the federation architecture. Facilitators can be viewed as representatives of one or more teams that facilitate the exchange of design information and knowledge in support of the design tasks they perform. In the federation architecture, design specialists collaborate by exchanging design information with others via their software agents, and by identifying and resolving design conflicts by negotiation. In addition to a discussion of the framework's primary components, its realization in an integrated distributed environment for collaborative building engineering is described.     

The myth of accelerating business processes through parallel job designs

This paper discusses postulated advantages of parallel job designs compared with sequential designs in business processes. Until now, the literature suggests an overall dominance of parallel designs. An analysis of relevant application domains, in which parallel tasks are prevalent in order to accelerate processes, offers two remarkable insights: (1) parallel tasks can but do not have to speed-up business processes; (2) coordination efforts may reduce or even invert potential performance gains. Thus, this paper thoroughly evaluates interdependencies between parallel designs and coordination efforts through simulation experiments. Several process patterns for order processing in a real-world example will be examined. The results offer noteworthy characteristics of parallel designs which extent the existing knowledge: (a) gains from parallelization are reduced with increasing process variability, (b) small increments in coordination efforts neutralize gains from parallelization, (c) in high work load situations, the resource capacity for the coordination task is a severe bottleneck, and (d) if the findings (a)–(c) are carefully considered, only the parallelization of multiple tasks leads to significant performance gains.     

Cognitive and synthetic behavior of avatars in intelligent virtual environments

In intelligent virtual environments (IVEs), it is a challenging research issue to provide the intelligent virtual actors (or avatars) with the ability of visual perception and rapid response to virtual world events. Modeling an avatar’s cognitive and synthetic behavior appropriately is of paramount important in IVEs. We propose a new cognitive and behavior modeling methodology that integrates two previously developed complementary approaches. We present expression cloning, walking synthetic behavior modeling, and an autonomous agent cognitive model for driving an avatar’s behavior. Facial expressions are generated using our own-developed rule-based state transition system. Facial expressions are further personalized for individuals by expression cloning. An avatar’s walking behavior is modeled using a skeleton model that is implemented by seven-motion sequences and finite state machines (FSMs). We discuss experimental results demonstrating the benefits of our approach.     

Caramba—A Process-Aware Collaboration System Supporting Ad hoc and Collaborative Processes in Virtual Teams

Organizations increasingly define many business processes as projects executed by virtual (project) teams, where team members from within an organization cooperate with outside experts. Virtual teams require and enable people to collaborate across geographical distance and professional (organizational) boundaries and have a somewhat stable team configuration with roles and responsibilities assigned to team members. Different people, coming from different organizations will have their own preferences and experiences and cannot be expected to undergo a long learning cycle before participating in team activities. Thus, efficient communication, coordination, and process-aware collaboration remain a fundamental challenge. In this paper we discuss the current shortcomings of approaches in the light of virtual teamwork (mainly Workflow, Groupware, and Project Management) based on models and underlying metaphors. Furthermore, we present a novel approach for virtual teamwork by tightly integrating all associations between processes, artifacts, and resources. In this paper we analyze (a) the relevant criteria for process-aware collaboration system metaphors, (b) coordination models and constructs for organizational structures of virtual teams as well as for ad hoc and collaborative processes composed out of tasks, and (c) architectural considerations as well as design and implementation issues for an integrated process-aware collaboration system for virtual teams on the Internet.     

Toward automated feature model configuration with optimizing non-functional requirements

ContextA software product line is a family of software systems that share some common features but also have significant variabilities. A feature model is a variability modeling artifact, which represents differences among software products with respect to the variability relationships among their features. Having a feature model along with a reference model developed in the domain engineering lifecycle, a concrete product of the family is derived by binding the variation points in the feature model (called configuration process) and by instantiating the reference model.ObjectiveIn this work we address the feature model configuration problem and propose a framework to automatically select suitable features that satisfy both the functional and non-functional preferences and constraints of stakeholders. Additionally, interdependencies between various non-functional properties are taken into account in the framework.MethodThe proposed framework combines Analytical Hierarchy Process (AHP) and Fuzzy Cognitive Maps (FCM) to compute the non-functional properties weights based on stakeholders’ preferences and interdependencies between non-functional properties. Afterwards, Hierarchical Task Network (HTN) planning is applied to find the optimal feature model configuration.ResultOur approach improves state-of-art of feature model configuration by considering positive or negative impacts of the features on non-functional properties, the stakeholders’ preferences, and non-functional interdependencies. The approach presented in this paper extends earlier work presented in [1] from several distinct perspectives including mechanisms handling interdependencies between non-functional properties, proposing a novel tooling architecture, and offering visualization and interaction techniques for representing functional and non-functional aspects of feature models.Conclusionour experiments show the scalability of our configuration approach when considering both functional and non-functional requirements of stakeholders.     

Multi-agent Mediator architecture for distributed manufacturing

A generic Mediator architecture for distributed task planning and coordination has been developed using multi-agent paradigms. In this approach, agents function autonomously as independent computing processes, and dynamic virtual clusters coordinate the agent's activities and decision making. This coordination involves dynamically created coordination agents and resource agents concurrently. The Mediator architecture contains three levels of these coordination agents: the template mediator, the data-agent manager, and the active mediator. The template mediator is the top-level global coordinator. This agent contains both the templates and the cloning mechanism to create the successively lower-level agents. Task plans are decomposed successively into subtasks, which are allocated to dynamically created agent clusters coordinated through data-agent managers and active mediators. Coordination of agent activity takes place both among the clusters and within each cluster. The system dynamically adapts to evolving manufacturing tasks, with virtual agent clusters being created as needed, and destroyed when their tasks are completed. The mediator architecture and related mechanisms are demonstrated using an intelligent manufacturing scheduling application. Both the machines and the parts involved in this production system are considered as intelligent agents. These agents use a common language protocol based on the Knowledge Query Manipulation Language (KQML). The generic Mediator approach can be used for other distributed organizational systems beyond the intelligent manufacturing application it was originally developed for.     

Training to improve virtual team communication

Abstract. Organizations are utilizing virtual teams, comprising workgroup members who communicate and collaborate with technology, to accomplish tasks. These teams are geographically distributed and communicate via computer-mediated communication systems (CMCS), and may never or rarely meet face-to-face. Relational links among team members have been found to be a significant contributor to the effectiveness of information exchange in the use of CMCS. In most cases, team members receive little or no training to improve the effectiveness of this form of communication. When training is used, it often focuses on software utilization skills, not on interpersonal communication dynamics. This paper discusses the effect of virtual team communication training on group interactions, especially for enhancing these relational links and thereby improving communication and information exchange in virtual teams. It was found that teams that were given appropriate training exhibited improved perceptions of the interaction process over time, specifically with regard to trust, commitment and frank expression between members. Discussion of the role of training on virtual team processes and outcomes is discussed and future research implications are presented.     

Task mapper and application-aware virtual machine scheduler oriented for parallel computing

We design a task mapper TPCM for assigning tasks to virtual machines, and an application-aware virtual machine scheduler TPCS oriented for parallel computing to achieve a high performance in virtual computing systems. To solve the problem of mapping tasks to virtual machines, a virtual machine mapping algorithm (VMMA) in TPCM is presented to achieve load balance in a cluster. Based on such mapping results, TPCS is constructed including three components: a middleware supporting an application-driven scheduling, a device driver in the guest OS kernel, and a virtual machine scheduling algorithm. These components are implemented in the user space, guest OS, and the CPU virtualization subsystem of the Xen hypervisor, respectively. In TPCS, the progress statuses of tasks are transmitted to the underlying kernel from the user space, thus enabling virtual machine scheduling policy to schedule based on the progress of tasks. This policy aims to exchange completion time of tasks for resource utilization. Experimental results show that TPCM can mine the parallelism among tasks to implement the mapping from tasks to virtual machines based on the relations among subtasks. The TPCS scheduler can complete the tasks in a shorter time than can Credit and other schedulers, because it uses task progress to ensure that the tasks in virtual machines complete simultaneously, thereby reducing the time spent in pending, synchronization, communication, and switching. Therefore, parallel tasks can collaborate with each other to achieve higher resource utilization and lower overheads. We conclude that the TPCS scheduler can overcome the shortcomings of present algorithms in perceiving the progress of tasks, making it better than schedulers currently used in parallel computing.     

Influence of contextual objects on spatial interactions and viewpoints sharing in virtual environments

Collaborative virtual environments (CVEs) are 3D spaces in which users share virtual objects, communicate, and work together. To collaborate efficiently, users must develop a common representation of their shared virtual space. In this work, we investigated spatial communication in virtual environments. In order to perform an object co-manipulation task, the users must be able to communicate and exchange spatial information, such as object position, in a virtual environment. We conducted an experiment in which we manipulated the contents of the shared virtual space to understand how users verbally construct a common spatial representation of their environment. Forty-four students participated in the experiment to assess the influence of contextual objects on spatial communication and sharing of viewpoints. The participants were asked to perform in dyads an object co-manipulation task. The results show that the presence of a contextual object such as fixed and lateralized visual landmarks in the virtual environment positively influences the way male operators collaborate to perform this task. These results allow us to provide some design recommendations for CVEs for object manipulation tasks.     

Emerging Cooperation With Minimal Effort: Rewarding Over Mimicking

This paper compares supervised and unsupervised learning mechanisms for the emergence of cooperative multiagent spatial coordination using a top-down approach. By observing the global performance of a group of homogeneous agents-supported by a nonglobal knowledge of their environment-we attempt to extract information about the minimum size of the agent neurocontroller and the type of learning mechanism that collectively generate high-performing and robust behaviors with minimal computational effort. Consequently, a methodology for obtaining controllers of minimal size is introduced and a comparative study between supervised and unsupervised learning mechanisms for the generation of successful collective behaviors is presented. We have developed a prototype simulated world for our studies. This case study is primarily a computer games inspired world but its main features are also biologically plausible. The two specific tasks that the agents are tested in are the competing strategies of obstacle-avoidance and target-achievement. We demonstrate that cooperative behavior among agents, which is supported only by limited communication, appears to be necessary for the problem's efficient solution and that learning by rewarding the behavior of agent groups constitutes a more efficient and computationally preferred generic approach than supervised learning approaches in such complex multiagent worlds     

Computational Coordination Mechanisms: A tale of a struggle for flexibility

Coordination mechanisms (CMs) can be defined as any kind of computable construct whose aim is to organize activities performed by a group of actors that are called to collaborate for some purpose or reason. As such, CMs can be observed, conceived for and applied in a vast number of coordinative practices in almost every work setting. The advent of information and communication technologies has raised the issue of how these technologies could be used to help cooperating actors governing the increasing complexity of collaboration in modern organizations. This issue has been at the core of CSCW from its foundation until today: the field studies therein conducted have highlighted the flexibility by which human beings master this complexity. The requirement of flexibility has become one of the necessary conditions to guarantee the effectiveness of any computer support of coordination. The paper presents the main paradigms and approaches that have been proposed to fulfil this challenging requirement. The story shows that this effort has really been a sort of a struggle for either conceptual and technological solutions that are still to be fully realized and generally adopted in the field of work.