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.     

A timed mobile agent planning approach for distributed information retrieval in dynamic network environments

The number of mobile agents and total execution time are two factors used to represent the system overhead that must be considered as part of mobile agent planning (MAP) for distributed information retrieval. In addition to these two factors, the time constraints at the nodes of an information repository must also be taken into account when attempting to improve the quality of information retrieval. In previous studies, MAP approaches could not consider dynamic network conditions, e.g., variable network bandwidth and disconnection, such as are found in peer-to-peer (P2P) computing. For better performance, mobile agents that are more sensitive to network conditions must be used. In this paper, we propose a new MAP approach that we have named Timed Mobile Agent Planning (Tmap). The proposed approach minimizes the number of mobile agents and total execution time while keeping the turnaround time to a minimum, even if some nodes have a time constraint. It also considers dynamic network conditions to reflect the dynamic network condition more accurately. Moreover, we incorporate a security and fault-tolerance mechanism into the planning approach to better adapt it to real network environments.     

Network-aware virtual machine migration in an overcommitted cloud

Virtualization, which acts as the underlying technology for cloud computing, enables large amounts of third-party applications to be packed into virtual machines (VMs). VM migration enables servers to be reconsolidated or reshuffled to reduce the operational costs of data centers. The network traffic costs for VM migration currently attract limited attention.However, traffic and bandwidth demands among VMs in a data center account for considerable total traffic. VM migration also causes additional data transfer overhead, which would also increase the network cost of the data center.This study considers a network-aware VM migration (NetVMM) problem in an overcommitted cloud and formulates it into a non-deterministic polynomial time-complete problem. This study aims to minimize network traffic costs by considering the inherent dependencies among VMs that comprise a multi-tier application and the underlying topology of physical machines and to ensure a good trade-off between network communication and VM migration costs.The mechanism that the swarm intelligence algorithm aims to find is an approximate optimal solution through repeated iterations to make it a good solution for the VM migration problem. In this study, genetic algorithm (GA) and artificial bee colony (ABC) are adopted and changed to suit the VM migration problem to minimize the network cost. Experimental results show that GA has low network costs when VM instances are small. However, when the problem size increases, ABC is advantageous to GA. The running time of ABC is also nearly half than that of GA. To the best of our knowledge, we are the first to use ABC to solve the NetVMM problem.     

Execution coordination in mobile agent-based distributed job workflow execution

Mobile agent-based distributed job workflow execution requires the use of execution coordination techniques to ensure that an agent executing a subjob can locate its predecessors’ execution results. This paper describes the classification, implementation, and evaluation of execution coordination techniques in the mobile agent-based distributed job workflow execution system. First, a classification of the existing execution coordination techniques is developed for mobile agent systems. Second, to put the discussion into perspective, our framework for mobile agent-based distributed job workflow execution over the Grid (that is, MCCF: Mobile Code Collaboration Framework) is described. How the existing coordination techniques can be applied in the MCCF is also discussed. Finally, a performance study has been conducted to evaluate three coordination techniques using real and simulated job workflows. The results are presented and discussed in the paper.     

Algorithms for validating E-tickets in mobile computing environment

E-tickets issued online can be used by different vendors to provide services such as discount coupons for E-shopping, or an entrance for a football game. One major issue associated with E-tickets is the problem of validation, which becomes more severe in a mobile environment due to mobility of a mobile host (MH) and frequent failure/disconnection of validation servers known as mobile support stations (MSSs). Some additional problems include the identification of duplicate submissions of an E-ticket by a MH. Thus, this paper proposes two protocols using the Flat and Hierarchical schemes for E-ticket processing and validation in a mobile environment that guarantee at least and at most once property (each E-ticket is validated at least and at most once). The protocols have been validated and compared through complexity analysis and experiments.     

一种基于移动Agent的分布式入侵检测系统模型MABDIDS

分析了当前的入侵检测技术的发展及存在的主要缺陷,介绍了移动Agent的概念及其优点,提出了一种新的基于移动Agent的分布式入侵检测模型MABDIDS。MABDIDS利用移动Agent的优点,设计了针对主机和网络两种环境而分别具有不同运行机制的两种检测主体,通过将多个监控节点组织成层次结构来协同实现分布式入侵检测,解决了当前分布式入侵检测系统中存在的主要问题。     

Perses: A framework for the continuous evaluation of the QoS of distributed mobile applications

The increasing capabilities of mobile devices have led to the emergence of new paradigms exploiting them. These paradigms foster the onload and distribution of functionalities on mobile devices, allowing the development of distributed mobile applications. This distribution reduces the latency and the data traffic overhead and improves privacy. As in any other mobile application, their success largely depends on the quality of service (QoS) they offer. Nevertheless, the evaluation of distributed mobile applications is particularly complex due to the number, heterogeneity, and interactions between the devices involved. Current techniques allow developers to assess the quality of a single device, but they are not designed for highly heterogeneous, distributed, and collaborative environments. This paper presents a framework called Perses, which allows the creation of virtual scenarios with multiple heterogeneous mobile devices to launch end-to-end tests to evaluate not only each device but also the interactions among them. The framework was evaluated against a real deployment, showing that the behavior and the quality attributes measured are similar to those of the real deployment, allowing developers to evaluate these applications before launching them. Finally, Perses was integrated into a DevOps methodology to automate its execution and further facilitate its adoption by software companies.     

A lightweight and distributed middleware to provide presence awareness in mobile ubiquitous systems

Several researchers have identified the need to count on presence awareness in ubiquitous systems that support mobile activities, particularly when these systems are used to perform loosely-coupled mobile work. In such a work style, mobile users conduct face-to-face on-demand interactions, therefore counting on awareness information about the position and availability of potential collaborators becomes mandatory for these applications. Most proposed solutions that provide user presence awareness involve centralized components, have reusability limitations, or simply address a part of that service. This article presents a lightweight and fully distributed middleware named Moware, which allows developers to embed presence awareness services in mobile ubiquitous systems in a simple way. The article also describes the Moware architecture, its main components and strategies used to deal with several aspects of the presence awareness support. These design strategies can be reused by software designers to provide presence awareness capabilities into middleware and specific software applications. Moware services were embedded in a mobile ubiquitous system that supports inspectors during the construction inspection process. The preliminary results indicate that the middleware was easy to use for developers, and its services were useful for the end-users.     

Team dynamics in virtual,partially distributed teams: Optimal role fulfillment

In this study, we explored team roles in virtual, partially distributed teams, or vPDTs (teams with at least one co-located subgroup and at least two subgroups that are geographically dispersed but that collaborate virtually). Past research on virtual teams emphasizes the importance of team dynamics. We argue that the following three roles are particularly important for high functioning virtual teams: Project Coordinator, Implementer and Completer-Finisher. We hypothesized that the highest performing vPDTs will have 1) a single Project Coordinator for each subgroup, 2) multiple Implementers within the team, and 3) fewer Completer-Finishers within the team. A sample of 28 vPDTs with members working on two different continents provides support for the second and third hypothesized relationships, but not the first.     

Simulation and control of distributed robot search teams

This article describes the simulation of distributed autonomous robots for search and rescue operations. The simulation system is utilized to perform experiments with various control strategies for the robot team and team organizations, evaluating the comparative performance of the strategies and organizations. The objective of the robot team is to, once deployed in an environment (floor-plan) with multiple rooms, cover as many rooms as possible. The simulated robots are capable of navigation through the environment, and can communicate using simple messages. The simulator maintains the world, provides each robot with sensory information, and carries out the actions of the robots. The simulator keeps track of the rooms visited by robots and the elapsed time, in order to evaluate the performance of the robot teams. The robot teams are composed of homogenous robots, i.e., identical control strategies are used to generate the behavior of each robot in the team. The ability to deploy autonomous robots, as opposed to humans, in hazardous search and rescue missions could provide immeasurable benefits.     

Implementing distributed control system for intelligent mobile robot

The control system of a mobile robot has a number of issues to deal with in real time, including motion control, mapping, localization, path planning, and sensor processing. Intelligent reasoning, task-oriented behaviors, human–robot interfaces, and communications add more tasks to be solved. This naturally leads to a complex hierarchical control system where various tasks have to be processed concurrently. Many low-level tasks can be handled by a robots onboard (host) computer. However, other tasks, such as speech recognition or vision processing, are too computationally intensive for one computer to process. In this case, it is better to consider a distributed design for the control system in networked environments. In order to achieve maximum use of the distributed environment, it is important to design and implement the distributed system and its communication mechanisms in an effective and flexible way. This article describes our approach to designing and implementing a distributed control system for an intelligent mobile robot. We present our implementation of such a distributed control system for a prototype mobile robot. We focus our discussion on the system architecture, distributed communication mechanisms, and distributed robot control.This work was presented, in part, at the 8th International Symposium on Artificial Life and Robotics, Oita, Japan, January 24–26, 2003     

DAMN: a distributed architecture for mobile navigation

An architecture is presented in which distributed task-achieving modules, or behaviours, cooperatively determine a mobile robot's path by voting for each of various possible actions. An arbiter then performs command fusion and selects that action which best satisfies the prioritized goals of the system, as expressed by these votes, without the need to average commands. Command fusion allows multiple goals and constraints to be considered simultaneously. Examples of implemented systems are given, and future research directions in command fusion are discussed.     

Dynamic partner identification in mobile agent-based distributed job workflow execution

This paper is concerned with the design, implementation, and evaluation of algorithms for communication partner identification in mobile agent-based distributed job workflow execution. We first describe a framework for distributed job workflow execution over the Grid: the Mobile Code Collaboration Framework (MCCF). Based on the study of agent communications during a job workflow execution on MCCF, we identify the unnecessary agent communications that degrade the system performance. Then, we design a novel subjob grouping algorithm for preprocessing the job workflow's static specification in MCCF. The obtained information is used in both static and dynamic algorithms to identify partners for agent communication. The mobile agent dynamic location and communication based on this approach is expected to reduce the agent communication overhead by removing unnecessary communication partners during the dynamic job workflow execution. The proof of the dynamic algorithm's correctness and effectiveness are elaborated. Finally, the algorithms are evaluated through a comparison study using simulated job workflows executed on a prototype implementation of the MCCF on a LAN environment and an emulated WAN setup. The results show the scalability and efficiency of the algorithms as well as the advantages of the dynamic algorithm over the static one.     

Identifying the ideal fit between mobile work and mobile work support

The rapid growth in the use of wireless communication and portable devices has created a potential for a variety of mobile work support. However, few studies have explored the nature of mobile work, examined the needs for its support, and identified the appropriate support for various kinds of work in mobile contexts. In our study, a mobile task model was proposed and tested, including three dimensions: mobility, location dependency, and time criticality. Four context-related mobile work support functions were examined: location tracking, navigation, notification, and online job dispatching. In the light of task-technology fit theory and attitude/behavioral theory, we proposed a research model for the fit between task characteristics and the four mobile work support functions. The ideal fit was analyzed on the basis of empirical data collected from a sample of mobile knowledge and field workers. Our study resulted in a theoretical contribution to task/technology fit theory in the context of mobile work support, and suggested guidelines for the development and use of mobile work support systems.     

Training individuals for distributed teams: problem solving assessment for distributed mission research

In this paper we describe an effort investigating the feasibility and utility of cognitively diagnostic assessment of problem solving when training for distributed team tasks. We utilized computer-based knowledge elicitation methods to assess both relational problem solving, requiring the semantic integration of concepts, and dynamic problem solving, requiring the ability to integrate and apply these concepts. Additionally, we addressed how metacognitive processes interact with learning outcomes when training for complex synthetic task environments. We find first, that multiple methods of assessing problem solving performance are diagnostic of knowledge acquisition for a complex synthetic team task, and second, that general metacomprehension predisposition is related to metacomprehension accuracy in synthetic task environments.     

Distributed reformation of core-based group-shared multicast trees in mobile ad hoc networks

This paper proposes a method to reduce the cost of a core-based group-shared multicast tree, where the cost is evaluated by the total bandwidth consumption of multicasting packets among all group members. Due to the broadcast nature of radio transmissions, we find that the challenge of determining minimum cost multicast tree can be approximated by finding the multicast tree with a minimum number of non-leaves (the minimum non-leaf multicast tree problem). However, we also find that the minimum non-leaf multicast tree problem is NP-complete. Thus, a method is proposed to dynamically reduce the number of non-leaves in an existing multicast tree. Experimental results show that our method reduces the cost of the multicast tree in both geometrically and randomly distributed network models and the random waypoint mobility model.     

PDAs and shared public displays: Making personal information public, and public information personal

We are investigating how people move from individual to group work through the use of both personal digital assistants (PDAs) and a shared public display. Our scenario of this work covers the following activities. First, mobile individuals can create personal notes on their PDAs. Second, when individuals meet in real time, they can selectively publicise notes by moving them to a shared public display. Third, the group can manipulate personal and public items in real time through both PDAs and the shared public display, where the notes contained on both PDAs and public display are automatically synchronised. Finally, people leave a meeting with a common record of their activity. We describe our SharedNotes system that illustrates how people move through this scenario. We also highlight a variety of problematic design issues that result from having different devices and from having the system enforce a rigid distinction between personal and public information.     

Team member selection decisions for virtual versus face-to-face teams

We compared the importance placed on task skills and four personal characteristics when selecting members of virtual and face-to-face teams. We expected that task skills would be most important in selection decisions for virtual teams due to the lack of physical proximity and visibility, whereas personal characteristics would be more important for face-to-face team selection. In a policy capturing study, 100 undergraduates’ decision policies indicated that task skills had a greater impact on selection decisions for virtual teams. Gender also influenced selection decisions, with women choosing more female than male applicants for both types of teams. Applicants’ race, physical attractiveness, and attitudinal similarity to participants did not influence selection decisions for either type of team; however, when assessed by self-report evaluations, these characteristics and gender, had a greater influence for face-to-face teams.     

Programming languages for distributed applications

Much progress has been made in distributed computing in the areas of distribution structure, open computing, fault tolerance, and security. Yet, writing distributed applications remains difficult because the programmer has to manage models of these areas explicitly. A major challenge is to integrate the four models into a coherent development platform. Such a platform should make it possible to cleanly separate an application’s functionality from the other four concerns. Concurrent constraint programming, an evolution of concurrent logic programming, has both the expressiveness and the formal foundation needed to attempt this integration. As a first step, we have designed and built a platform that separates an application’s functionality from its distribution structure. We have prototyped several collaborative tools with this platform, including a shared graphic editor whose design is presented in detail. The platform efficiently implements Distributed Oz, which extends the Oz language with constructs to express the distribution structure and with basic primitives for open computing, failure detection and handling, and resource control. Oz appears to the programmer as a concurrent object-oriented language with dataflow synchronization. Oz is based on a higher-order, state-aware, concurrent constraint computation model. Seif Haridi, Ph.D.: He received his Ph.D. in computer science in 1981 from the Royal Institute of Technology, Sweden. After spending 18 months at IBM T. J. Watson Research Center, he moved to the Swedish Institute of Computer Science (SICS) to form a research lab on logic programming and parallel systems. Dr. Haridi is currently the research director of the Swedish Institute of Computer Science. He has been an active researcher in the area of logic and constraint programming and parallel processing since the beginning of the eighties. His earlier work includes contributions to the design of SICStus Prolog, various parallel Prolog systems and a class of scalable cache-coherent multiprocessors known as Cache-Only Memory Architecture (COMA). During the nineties most of his work focused on the design of multiparadigm programming systems based on Concurrent Constraint Programming (CCP). Currently, he is interested in programming systems and software methodology for distributed and agent-based applications. Peter Van Roy, Ph.D.: He obtained an engineering degree from the Vrije Universiteit Brussel (1983), Masters and Ph.D. degrees from the University of California at Berkeley (1984, 1990), and the Habilitation à Diriger des Recherches from Paris VII Denis Diderot (1996). He has made major contributions to logic language implementation. His research showed for the first time that Prolog can be implemented with the same execution efficiency as C. He was principal developer or codeveloper of Aquarius Prolog, Wild_Life, Logical State Threads, and FractaSketch. He joined the Oz project in 1994 and is currently working on Distributed Oz. His research interests are motivated by the desire to provide increased expressivity and efficiency to application developers. Per Brand: He is a researcher at the Swedish Institute of Computer Science. He has previously worked on the design and implementation of OR-parallel Prolog (the Aurora project) and optimized compilation techniques for Concurrent Constraint Programming Languages (in particular, AKL). He has been a member of the Distributed Oz design team since the project began. His research interests are focused on techniques, languages, and methodology for distributed programming. Christian Schulte: He studied computer science at the University of Karlsruhe, Germany, from 1987 to 1992 where he received his diploma. Since 1992 he has been a member of the Programming Systems Lab at DFKI. He is one of the principal designers of Oz. His research interests include design, implementation, and application of concurrent and distributed programming languages as well as constraint programming.     

Using cooperative mobile agents to monitor distributed and dynamic environments

Monitoring the changes in data values obtained from the environment (e.g., locations of moving objects) is a primary concern in many fields, as for example in the pervasive computing environment. The monitoring task is challenging from a double perspective. First and foremost, the environment can be highly dynamic in terms of the rate of data changes. Second, the monitored data are often not available from a single computer/device but are distributed; moreover, the set of data providers can change along the course of time. Therefore, obtaining a global snapshot of the environment and keeping it up-to-date is not easy, especially if the conditions (e.g., network delays) change.In this article, a decentralized, loose, and fault-tolerant monitoring approach based on the use of mobile agents is described. Mobile agents allow easy tracking of the involved computers, carrying the monitoring tasks to wherever they are needed. A deadline-based mechanism is used to coordinate the cooperative agents, which strive to perform their continuous tasks in time while considering data as recent as possible, constantly adapting themselves to new environmental conditions (changing communication and processing delays). This approach has been successfully used in a real environment and experiments were carried out to prove its feasibility and benefits.