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Much research in artificial intelligence is concerned with the development of autonomous agents that can interact effectively with other agents. An important aspect of such agents is the ability to reason about the behaviours of other agents, by constructing models which make predictions about various properties of interest (such as actions, goals, beliefs) of the modelled agents. A variety of modelling approaches now exist which vary widely in their methodology and underlying assumptions, catering to the needs of the different sub-communities within which they were developed and reflecting the different practical uses for which they are intended. The purpose of the present article is to provide a comprehensive survey of the salient modelling methods which can be found in the literature. The article concludes with a discussion of open problems which may form the basis for fruitful future research. [ABSTRACT FROM AUTHOR]

In this paper, we investigate consensus and disturbance attenuation in a chain of mobile agents, which include non-autonomous agents, semi-autonomous agents and autonomous agents. In particular, the nonlinear dynamics of non-autonomous agents is given and cannot be designed, while the dynamics of semi-autonomous and autonomous agents can be partially and fully designed, respectively. To improve the robustness of multi-agent chains against disturbances, we propose a nonlinear control framework for semi-autonomous and autonomous agents such that they mimic the behavior of non-autonomous agents for compatibility while also exploiting long-range connections with distant agents. This framework ensures the existence of a unique consensus equilibrium, which is independent of the network size, connectivity topologies, control gains and information delays. Robustness of multi-agent chains against disturbances is investigated by evaluating the frequency response at the nonlinear level. For infinitely long multi-agent chains with recurrent patterns, we also derive a condition that ensures the disturbance attenuation but only requires the analysis of the linearized model. A case study is conducted for a connected vehicle system where numerical simulations are used to validate the analytical results. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The performance of physical assets has become a major determinant success factor for urban flood control. However, managing these assets is always challenging as there are a huge number of diverse assets involved, which are distributed throughout the city, and owned by different agencies. Aiming at improving the management efficiency of these assets, and ensuring their performance, this paper proposes the concept of cloud asset based on cloud computing, mobile agent, and various smart devices. Through hardware integration and software encapsulation, cloud asset could sense its real-time status, adapt to varied working scenarios, be controlled remotely, and shared among agencies. It enables accurate real-time control of every asset, and thus improves the management efficiency and effectiveness. This paper first presents the concept of cloud asset with its technical architecture, and then analyses the software agent model for cloud asset, which is the key enabler to realize UPnP (Universal Plug and Play) management of assets, and provides mobility and intelligence for them. After that, the framework of cloud asset-enabled workflow management is built, in which cloud asset could be easily found and dynamically invoked by different workflows. Finally, a demonstrative case is provided to verify the effectiveness of cloud asset. [ABSTRACT FROM AUTHOR]

Two mobile agents starting at different nodes of an unknown network have to meet. This task is known in the literature as rendezvous. Each agent has a different label which is a positive integer known to it but unknown to the other agent. Agents move in an asynchronous way: the speed of agents may vary and is controlled by an adversary. The cost of a rendezvous algorithm is the total number of edge traversals by both agents until their meeting. The only previous deterministic algorithm solving this problem has cost exponential in the size of the graph and in the larger label. In this paper we present a deterministic rendezvous algorithm with cost polynomial in the size of the graph and in the length of the smaller label. Hence, we decrease the cost exponentially in the size of the graph and doubly exponentially in the labels of agents. As an application of our rendezvous algorithm we solve several fundamental problems involving teams of unknown size larger than 1 of labeled agents moving asynchronously in unknown networks. Among them are the following problems: team size, in which every agent has to find the total number of agents; leader election, in which all agents have to output the label of a single agent; perfect renaming, in which all agents have to adopt new and different labels from the set {1,...,k}, where k is the number of agents; and gossiping, in which each agent has initially a piece of information (value) and all agents have to output all the values. Using our rendezvous algorithm, we solve all of these problems at cost polynomial in the size of the graph and in the smallest length of all labels of participating agents. [ABSTRACT FROM AUTHOR]

A review of popular technology adoption models identified several factors that are likely to influence Voice Activated Personal Assistant (VAPA) use in public spaces. To inform design decisions of how to make the private use of the VAPA in public spaces more acceptable from the users’ point of view, an online survey was conducted to investigate the likelihood of usage of the smartphone VAPA such as Apple’s Siri (compared to the usage of smartphone keyboard) as a function of location (private vs. public) and type of information (private vs. nonprivate). Responses from participants showed that users were more cautious of transmitting private than nonprivate information. This effect of type of information was amplified in the social context of public locations and when using conspicuous methods of information input such as the VAPA. Participants also preferred using the VAPA in private locations and showed no preference of location for keyboard entries. Correlations between likelihood of usage of VAPA and the social acceptability ratings were positive and predicted similar patterns of smartphone usage. [ABSTRACT FROM PUBLISHER]

Mobile agent is a distributed program which can move autonomously in a network, to perform its tasks, on behalf of the user. During migration, the mobile agents and so its data are susceptible to failures due to the faults in the network components like the machine and the channel. It is a challenging issue to address the mobile agent failure scenario during its migration. This paper presents a failure recovery model for mobile agents that ensure the recovery of the lost mobile agent and the data. This is done by allowing a replication of the actual mobile agent at the previously visited servers. However, unlike existing methods, in this paper the replication is temporary and limited to an optimal value. This is achieved by making the mobile agents that operates in multi-region environment, to track, communicate and share the retrieved information between them. After the information sharing, in this paper, the number of replica to be maintained at each region is reduced to one. Furthermore, as there is at least one server in each region that holds the replica, this paper guarantees that the information collected at each server is not lost. In addition, the presented model survives the region failure too, when implemented in a multi-region environment. Experiments were conducted in a web environment, and the results obtained are analyzed and compared with existing methods, based on different testing parameters. The experimental results appear to be more encouraging in claiming the presented recovery model to be a reliable one. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the relation between the (ideal) time and space complexities for the gathering problem with anonymous agents in asynchronous anonymous tree networks. The gathering problem requires that all the agents in the network have to meet at a single node within a finite time. Although an asymptotically space-optimal algorithm is known, its time complexity is quite large. In this paper, we consider asymptotically (ideal-)time-optimal algorithms and investigate the minimum memory requirement per agent for asymptotically time-optimal algorithms. First, we show that there exists a tree with nodes in which bits of memory per agent is required to solve the gathering problem in time (asymptotically time-optimal). Then, we present an asymptotically time-optimal gathering algorithm. This algorithm can be executed if each agent has bits of memory. From this lower/upper bound, this algorithm is asymptotically space-optimal on the condition that the time complexity is asymptotically optimal. [Copyright &y& Elsevier]

Abstract: Nowadays wireless body sensor networks (WBSNs) have great potential to enable a broad variety of assisted living applications such as human biophysical/biochemical control and activity monitoring for health care, e-fitness, emergency detection, emotional recognition for social networking, security, and highly interactive games. It is therefore important to define design methodologies and programming frameworks which enable rapid prototyping of WBSN applications. Several effective application development frameworks have been already proposed for WBSNs designed for TinyOS-based sensor platforms, e.g. CodeBlue, SPINE, and Titan. In this paper we present an application of MAPS, an agent framework for wireless sensor networks based on the Java-programmable Sun SPOT sensor platform, for the development of a real-time WBSN-based system for human activity monitoring. The agent-oriented programming abstractions provided by MAPS allow effective and rapid prototyping of the sensor-side software. In particular, the architecture of the developed system is a typical star-based WBSN composed of a coordinator node and two sensor nodes located respectively on the waist and the thigh of the monitored assisted living. The coordinator relies on a JADE-based enhancement of the SPINE coordinator and allows configuring sensors, receiving their data, and recognizing pre-defined human activities. On the other hand, each sensor node runs a MAPS-based agent that performs sensing of the 3-axial accelerometer sensor, computation of significant features on the acquired data, feature aggregation and transmission to the coordinator. The experimentation phase of the prototype, which allows evaluating the obtainable monitoring performances and activity recognition accuracy, is described. Moreover, a comparison of the monitoring system based on MAPS, AFME and SPINE in terms of programming effectiveness and system performances is discussed. [Copyright &y& Elsevier]

A wireless sensor network (WSN) consists of spatially distributed nodes that monitor physical conditions. Thus far, WSNs have been constructed for specific applications. However, in the future, system operators may want an existing WSN to deploy simultaneous applications. Existing studies have demonstrated the effectiveness of applying mobile agents to enable simultaneous applications in WSNs. However, two problems make the present form of mobile agents impractical for applications involving cooperation and group migration by mobile agents. The first problem is the lack of a suitable architecture enabling cooperation and interaction between agents, and the second is the lack of an efficient way of achieving group migration by agents in WSNs. To address these problems, we propose an architecture organized by mobile agents that has specific functionalities and that enables group migration by multiple agents. [ABSTRACT FROM AUTHOR]

When an emergency occurs within a building, it is safer to send autonomous mobile agents instead of human responders, to explore the area and identify hazards and victims. Existing exploration algorithms (Svennebring, J. and Koenig, S. (2004) Building terrain-covering Ant robots: a feasibility study. Auton. Robots, 16, 313–332, Ferranti, E., Trigoni, N. and Levene, M. (2007) Brick&Mortar: An On-Line Multi-Agent Exploration Algorithm. ICRA07: Proc. 2007 IEEE Int. Conf. Robotics and Automation, April, pp. 761–767. IEEE Press) allow mobile agents to make distributed navigation decisions by communicating with nearby fixed sensors embedded in the environment. These algorithms are very efficient in terms of exploration time, but they have only been evaluated in simulation environments, where idealized assumptions were made regarding the ability of agents to localize sensors and move accurately towards them. The objective of this work is to investigate practical issues of building a real testbed of mobile agents and fixed sensors, and implementing exploration algorithms in such a testbed. In particular, we describe our experiences from building a real system consisting of a Surveyor SRV-1 robot and Tmote Sky sensors running the Contiki OS (Dunkels, A., Gron̈vall, B. and Voigt, T. (2004) Contiki — A Lightweight and Flexible Operating System for Tiny Networked Sensors. Proc. 1st Annual IEEE Int. Workshop on Embedded Networked Sensors, November, pp. 455–462). We select two existing exploration algorithms, Ants (Svennebring, J. and Koenig, S. (2004) Building terrain-covering Ant robots: a feasibility study. Auton. Robots, 16, 313–332) and Brick&Mortar (Ferranti, E., Trigoni, N. and Levene, M. (2007) Brick&Mortar: An On-Line Multi-Agent Exploration Algorithm. ICRA07: Proc. 2007 IEEE Int. Conf. Robotics and Automation, April, pp. 761–767. IEEE Press), and discuss challenges in trying to implement them in our testbed. To address these challenges, we propose practical solutions that allow a mobile agent to: (i) identify and localize fixed sensors deployed in its vicinity and (ii) accurately move towards a carefully selected fixed sensor. Using our real network deployment, we derive realistic models of localization and odometry errors. We then insert these error models into a realistic simulation environment, in order to extensively compare Ants and Brick&Mortar, and measure their performance degradation as a result of introducing realistic errors. [ABSTRACT FROM AUTHOR]

Abstract: Once a big repository of static data, the Web has been gradually evolved into a worldwide network of information and services known as the Semantic Web. This environment allows programs to autonomously interact with Web-accessible information and services. In this sense, mobile agent technology could help in efficiently exploiting this relatively new Web in a fully automated way, since Semantic Web resources are described in a computer-understandable way. In this paper, we present SWAM, a platform for building and deploying Prolog-based intelligent mobile agents on the Semantic Web. The article also reports examples and experimental results in order to illustrate as well as to assess the benefits of SWAM. [ABSTRACT FROM AUTHOR]

Abstract: With the evolution in the computer networks, many companies are trying to come up with efficient products which can make life easier for network administrators. Silent automated installation is one category among such products. In this paper, we have proposed silent network installer and tester (SNIT) which provides silent, automated and intelligent installation of software(s) over the network. SNIT will intelligently install any kind of software on request of the network administrator. SNIT not only provides installation services, it also enables network administrators to verify the installation of software over the network. SNIT uses an efficient algorithm to transfer the software installation setup on the network nodes. The system is fully autonomous and does not require any kind of user interaction or intervention. Network administrator is responsible for assigning the task(s) to SNIT and once assigned it performs the task(s) over the network autonomously with the help of intelligent mobile agents. SNIT has been deployed for evaluation purpose at the University Campus Lab equipped with 200 machines and some of the popular softwares were tested in the lab, results were very promising and support the implementation of the solution. [Copyright &y& Elsevier]

Abstract: We consider a fixed, undirected, known network and a number of “mobile agents” which can traverse the network in synchronised steps. Some nodes in the network may be faulty and the agents are to find the faults and repair them. The agents could be software agents, if the underlying network represents a computer network, or robots, if the underlying network represents some potentially hazardous physical terrain. Assuming that the first agent encountering a faulty node can immediately repair it, it is easy to see that the number of steps necessary and sufficient to complete this task is , where is the number of nodes in the network, is the diameter of the network, and is the number of agents. We consider the case where one agent can repair only one faulty node. After repairing the fault, the agent dies. We show that a simple deterministic algorithm for this problem terminates within steps, where , assuming that the number of faulty nodes is at most . We also demonstrate the worst-case asymptotic optimality of this algorithm by showing a network such that for any deterministic algorithm, there is a placement of faults forcing the algorithm to work for steps. [Copyright &y& Elsevier]

We have been proposing the automatic human tracking system to overcome limitations of existing video surveillance systems. This paper proposes two bypass methods to keep tracking a targeted person by the system constructed by using mobile agent technologies even if unexpected problems are occurred. The proposed methods are called as "Recalculation Bypass Method" and "Additional Calculation Bypass Method". These bypass methods utilize the algorithm which is elaborated in the paper, "An Algorithm to Determine Neighbor Nodes" [7]. The mobile agents are operating in automatic human tracking system and the bypass methods are utilized by the mobile agents. It is a very important ability for the mobile agent not to lose tracking in automatic human tracking systems. The bypass methods contribute to the realization of robust system and resolve two classifications of problem to ensure the tracking ability of mobile agents. The two classifications of problem are logical and physical problems. In the case of logical problems, they occur inside the system and they are called as "broken server". While in the case of physical problems, they occur outside the system and they are called as "pathway being modified". This system is able to track the targeted person continuously by utilizing the methods even if unexpected problems are occurred. We confirmed the effectiveness of the proposed bypass methods by the experiments that used more than one broken servers and pathway being modified. [ABSTRACT FROM AUTHOR]

The Virtual Home Environment is very important in contemporary mobile telecommunications infrastructure as it caters for the ubiquitous provision of services irrespective of network, location and user device. The universality of systems like Universal Mobile Telecommunications System and wi-fi increases the need for the rapid introduction of efficient VHE schemes. In this paper, we study the adoption of Mobile Agents for handling the VHE functionality. Mobile agents are nicely harmonized with the broader idea of VHE as they allow the autonomous execution of tasks by components that roam from node to node and network to network. We present the detailed modeling of a VHE provisioning architecture and investigate its suitability for different use cases and technical options (e.g., end user devices). The adoption of mobile agents for the ubiquitous provision of telecommunication services is quite promising in terms of efficiency. Through a series of experiments we quantify the performance benefits stemming from the adoption of mobile agents in contrast to conventional service provisioning schemes. [ABSTRACT FROM AUTHOR]

The article presents a study on the collective social strategies for the diffusion of multiagents. It highlights the use of two kinds of diffusions which are the collective insurgence, as well as the elite diffusions that are modelled through setting the variables in the formal framework. It explores the concurrent forms of collective diffusion, while social strategies are determined by other diffusion processes on other agents. It focuses on the spatial diffusion model assuming that all agents can be found in an Euclidian space wherein the social distances between agents can be measured.

Intrusion Detection Systems (IDS) is defined as a component that analyses system and user operations in computer and network systems in search of activities considered undesirable from security perspectives. Applying mobile agent (MA) to intrusion detection design is a recent development and it is aimed at effective intrusion detection in distributed environment. From the literature, it is clear that most MA-based IDS that are available are not quite effective because their time to detection is high and detect limited intrusions. This paper proposes a way of classifying a typical IDS and then strategically reviews the existing mobile agent-based IDSs focusing on each of the categories of the classification, for example architecture, mode of data collection, the techniques for analysis, and the security of these intelligent codes. Their strengths and problems are stated wherever applicable. Furthermore, suggested ways of improving on current MA-IDS designs are presented in order to achieve an efficient mobile agent-based IDS for future security of distributed network. [ABSTRACT FROM AUTHOR]

In some applications, as part of a mobile agent mission, there may be the necessity of meeting a firm end-to-end deadline, although with some itinerary flexibility due to optional resources. This paper proposes an execution model based on the concept of imprecise mobile agents with timing constraints. In this paper it is considered an execution model where agents do not previously know their itineraries. The imprecise mobile agent may choose among alternative and/or optional resources. The objective is to propose and to evaluate heuristics to be used individually or in pairs by imprecise mobile agents that must accomplish a mission within a firm deadline. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Security in host-based computing continues to be an area of regular research. Problems in host-based security exist in three principal areas: application protection, host environment protection, and data protection. These three areas echo the security issues for mobile agents: protecting agents from hostile hosts, protecting hosts from agents, and protecting data in transit as identified in Vuong and Peng (2001). Mobile agents are specialized applications which travel between hosts. Mobility is achieved by passing data and execution parameters from one host to another. A parallel can be drawn between mobile agents and host-based applications considering both perform host-based computations. In this paper we regard the security challenges for mobile agents equivalent to those of applications installed on a host. Furthermore, we also consider a circular threat that exists between applications and the host environment. [ABSTRACT FROM AUTHOR]

The service-oriented modeling and architecture modeling environment (SOMA-ME) is first a framework for the model-driven design of service-oriented architecture (SOA) solutions using the service-oriented modeling and architecture (SOMA) method. In SOMA-ME, Unified Modeling Language (UMLe) profiles extend the UML 2.0 metamodel to domain-specific concepts. SOMA-ME is also a tool that extends the IBM Rationalt Software Architect product to provide a development environment and automation features for designing SOA solutions in a systematic and model-driven fashion. Extensibility, traceability, variation-oriented design, and automatic generation of technical documentation and code artifacts are shown to be some of the properties of the SOMA-ME tool. [ABSTRACT FROM AUTHOR]

We present a model of the establishment and maintenance of communication between mobile agents. We assume that the agents move through a fixed environment modeled by a motion graph and are able to communicate if they are within distance at most d of each other. As the agents move randomly, we analyze the evolution in time of the connectivity between a set of w agents, asymptotically for a large number N of vertices, when w also grows large. The particular topologies of the environment we study here are the cycle and the toroidal grid. [ABSTRACT FROM AUTHOR]

As a recently emerging distributed computing paradigm, mobile-agent technology attracts great interests because of its salient merits. However, it also brings significant security concerns, among which the security problems between a mobile agent and its platforms are of primary importance. While protecting a platform (platform or host security) can benefit from the security measures in a traditional client-server system, protecting a mobile agent (mobile-agent or code security) has not been met in traditional client-server systems and is a new area emerging with mobile-agent technology. Mobile-agent security is also believed to be the most difficult in the security areas of a mobile-agent system. Several methods are proposed to provide protection or detection mechanisms for mobile-agent security. However, many of them either lack an intuitive formal approach to formally model and analyze the system or lack security consideration for mobility-the most distinct characteristic of a mobile agent. In this paper, we extended the original elementary object system (EOS), which applies object-oriented technology to Petri nets, in several aspects because the original EOS cannot fully support the features of mobile-agent system and security modeling. Based on the extended EOS (EEOS), we developed a formal model for a generic secure mobile-agent system. This model supports not only strong mobility but also secure mobility of a mobile agent. Mutual authentication between a mobile agent and its hosting platform is accomplished in this model. Meanwhile, a security mechanism is presented for the detection of malicious platform attacks to mobile-agent code or execution flow during the mobile- agent execution. Using an intuitively graphical formal method to model, simulate, and analyze a secure mobile-agent system distinguishes this paper from other works on mobile-agent security. This paper also introduces how to translate our EEOS model to a colored Petri net (CPN) model and presents the simulation of a sample mobile-agent system model in Design/CPN Different from the mathematical or theorem-proving analysis methods used by other mobile-agent system and mobility models, we used simulation-based analysis to verify several characteristics including boundedness, liveness, concurrence, and security of the system. Compared with other analysis methods, simulation-based analysis is generally more intuitive and more widely used in industry to solve real problems. [ABSTRACT FROM AUTHOR]

A mobile agent is an important platform for applications for the coming ubiquitous society. Many different kinds of mobile agent platforms have been developed. However, agents from one agent platform are generally not able to migrate into another agent platform. As a solution to this problem, we propose an interoperability concept using an incarnation agent. The concept realizes logical mobility within different kinds of agent platforms. The incarnation agent extracts an agent's procedures and status, compiling them into agent platform independent format and then re-compiling them to target agent platform format, thus enabling the process to continue. The incarnation agent also has autonomy for interoperability. It manages complex migration for interoperability, so agent's procedure can be described in simple mobile model. Moreover, the incarnation agent modifies agent's procedures as applicable to facilities of target agent platform. This paper also reports an interoperability middle-ware and its examination. The middle-ware is a foundation of realizing the Incarnation Agent, and the response time and network traffic overheads by the interoperability middle-ware has been measured. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(4): 49–59, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20388 [ABSTRACT FROM AUTHOR]

We coordinate in discrete time the interaction of two heterogeneous groups of mobile agents: a group of ground vehicles (ugvs) and a group of aerial vehicles (uavs). The ground agents interact with each other through time-invariant, nearest-neighbour rules. They synchronize their velocities through a specific communication protocol, and maintain cohesion and separation behaviour by means of interagent potential forces. Ground vehicles estimate their formation’s centroid using only locally available delayed information. That same information is transmitted to the aerial group, which orbits above the ground formation’s centroid, while avoiding midair collisions. Stability of the ground group motion is established in a Lyapunov framework. A Lyapunov analysis is also used to ensure that uavs track the ground group’s centroid. [Copyright &y& Elsevier]

A black hole is a highly harmful stationary process residing in a node of a network and destroying all mobile agents visiting the node without leaving any trace. The Black Hole Search is the task of locating all black holes in a network by exploring it with mobile agents. We consider the problem of designing the fastest Black Hole Search, given the map of the network and the starting node. We study the version of this problem that assumes that there is at most one black hole in the network and there are two agents, which move in synchronized steps. We prove that this problem is NP-hard in arbitrary graphs (even in planar graphs), solving an open problem stated in [J. Czyzowicz, D. Kowalski, E. Markou, A. Pelc, Searching for a black hole in tree networks, in: Proc. 8th Int. Conf. on Principles of Distributed Systems, OPODIS 2004, 2004, pp. 34–35. Also: Springer LNCS, vol. 3544, pp. 67–80]. We also give a -approximation algorithm, showing the first non-trivial approximation ratio upper bound for this problem. Our algorithm follows a natural approach of exploring networks via spanning trees. We prove that this approach cannot lead to an approximation ratio bound better than 3/2. [Copyright &y& Elsevier]

In this paper we consider a network where an intruder is moving "contaminating" the nodes it passes by, and we focus on the problem of decontaminating such a network by a team of mobile agents. The contamination/decontamination process has the following asynchronous dynamics: when the team is deployed all nodes are assumed to be contaminated, when an agent transits on a node, it will clean the node, when the node is left with no agent, the node will be recontaminated as soon as at least one of its neighbours is contaminated. We study the problem in asynchronous chordal ring networks and in tori. We consider two variations of the model: one where agents have only local knowledge, the other in which they have "visibility", i.e., they can "see" the state of their neighbouring nodes. We first derive lower bounds on the minimum number of agents necessary for the decontamination. In the case of chordal rings we show that the number of agents necessary to perform the cleaning does not depend on the size of the network; in fact it is linear in the length of the longest chord (provided that it is not too long). In the case of a torus, the minimum number of agents is equal to 2 · h, where h is the smallest dimension. We then propose optimal strategies for decontamination and we analyse the number of moves and the time complexity of the decontamination algorithms, showing that the visibility assumption allows us to decrease substantially both complexity measures. Another advantage of the "visibility model" is that agents move independently and autonomously without requiring any coordination. [ABSTRACT FROM AUTHOR]

Responsive environments are physical surroundings whose components change their behavior to accommodate the presence of people as well as other components. We describe a means to manage responsive environments whereby each component is dynamically assigned a software agent. Software agents are autonomous and reactive/proactive programs that communicate via message-passing. Arbitrary functionalities can be encoded in such agents, reflecting the capabilities of the components they represent, as well as extending them. Ours is a flexible and scalable approach allowing the gradual population of environments with physical devices and their agents. [ABSTRACT FROM AUTHOR]

This paper presents the operational semantics of an agent-oriented programming language called CLAIM. CLAIM allows to design multi-agent systems that support both stationary and mobile agents, endowed with cognitive capabilities and able to communicate. The semantics takes into account agents' reasoning, mobility, communication and concurrence, and contains a set of reduction rules between coherent states of a program. The operational semantics is a first step towards the formal verification of agent-based programs written in CLAIM. The reduction rules are illustrated on a case study. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach for enabling agents to learn to cooperate each other based on annotation and reward in Multi-Agent Systems (MAS). We propose two methods toward cooperation learning in MAS: 1) a cooperation method, and 2) a learning method. As for 1), our method enables each agent to interact with other agents by sending its proposal and receiving the counterproposals for the proposal from the agents. The counterproposals are constructed by modifying the communicated proposal, and are utilized for clarifying the difference in opinions among agents. Conflict resolution is conducted to reduce the difference to facilitate cooperation. Furthermore, annotation, which acts as a kind of design rationale, is added onto the communicated proposal and counterproposals to facilitate conflict resolution. As for 2), we propose an extension of reinforcement learning method so that agents can learn the appropriate behavior based on the reward which is given through the interaction among agents. We define two kinds of reward for each agent: the reward for the proposal constructed by the agent, and the reward for coherence among agents. Comparative simulation studies for micro satellite design, which fits for cooperative problem solving by MAS, were conducted to evaluate the proposed approach. The results are encouraging and show that it is worth following this path. Especially, the results indicate that the appropriate balance between exploration and exploitation, which is important in cooperative problem solving in general, can be learned with the proposed approach. [ABSTRACT FROM AUTHOR]

Logics for expressing properties of Petri hypernets, a visual formalism for modelling mobile agents, are proposed. Two classes of properties are of interest – the temporal evolution of agents and their structural correlation. In particular, we investigate how the classes can be combined into a logic capable of expressing the dynamic evolution of the structural correlation. The problemof model checking properties of a class of the logic on Petri hypernets is shown to be PSPACE-complete. [ABSTRACT FROM AUTHOR]

A black hole is a highly harmful stationary process residing in a node of a network and destroying all mobile agents visiting the node, without leaving any trace. We consider the task of locating a black hole in a (partially) synchronous network, assuming an upper bound on the time of any edge traversal by an agent. The minimum number of agents capable to identify a black hole is two. For a given graph and given starting node we are interested in the fastest possible black hole search by two agents, under the general scenario in which some subset of nodes is safe and the black hole can be located in one of the remaining nodes. We show that the problem of finding the fastest possible black hole search scheme by two agents is NP-hard, and we give a 9.3-approximation for it. [ABSTRACT FROM AUTHOR]

The mobility of agents is a distinct characteristic of mobile agent systems. Meanwhile, it has introduced new security issues. In this paper, we analyze the impact of an agent's path history (PH), as a resulting attribution of its mobility, on the access control decisions against it. The path could be an authorization basis. At the same time, the validity of the statically defined trust relationship with mobile agents is to be re-evaluated respecting where they have been, in which case the path information serves as a debasement of agents' trust degree and, therefore, weakens their privileges. To build a path-history-based access control model for the mobile agent application environment, path pattern and host patch are proposed here as conceptional components to declare the dynamic trust relationship with the migrating agents in a flexible and fine-grained manner. An integration of these two components with the well-known RBAC model is presented formally as a phRBAC model. Several application scenarios of phRBAC show its ability to enforce the special security policy in mobile agent environment. Some issues in implementing such a model are also discussed. [ABSTRACT FROM AUTHOR]

Multimedia synchronization control is essential to overcome the network delay variance problem in order to provide continuous and smooth playout of a multimedia stream. This paper proposes an agent-based intrastream synchronization scheme, which adapts to network delay fluctuations for continuous and smooth playout of a multimedia stream. The scheme employs three types of agents: application manager agent (AMA), user agent (UA) and negotiation/renegotiation mobile agents (NMAs/RMAs). AMA creates UA, NMAs and RMAs. UA monitors the synchronization parameters (delays, rate of change of delays, losses, etc.) as well as studies the user expectations. The NMAs/RMAs are used to negotiate/renegotiate synchronization parameters. The scheme operates in two phases: start-up synchronization and resynchronization. In start-up synchronization phase, a NMA is created by AMA to negotiate the delays and rate of change of delays with the intermediate nodes in the network on the basis of application requirements. In resynchronization phase, a RMA is created by AMA to renegotiate the delay parameters and resynchronize the presentation units of a stream, whenever UA reports violation of application requirements. Also, resynchronization phase takes care of link failures. The scheme is simulated in several network scenarios for verifying its operation effectiveness. It maintained the synchronization parameters well within the sustainable values. The benefits of the scheme are: asynchronous delay negotiation and adaptation, flexibility, adaptability and supports component based software development. [ABSTRACT FROM AUTHOR]

Reliability estimation of mobile agent-based systems remains a difficult task due to the characteristics of mobile agents that include distributed and asynchronous execution, autonomy, and mobility. In this paper we present an analytical approach to estimate the reliability of mobile agent-based systems. We define the reliability of a mobile agent in terms of the processor execution time required to perform agent's tasks at each processing node and the transmission or communication time needed to transfer the agent from one processing node to another via a network to complete its mission. The failure of entire components causes failure of the agent. Simulation experiments have been conducted using stochastic Petri Nets modeling. We investigate the effect of different component reliability and availability models (processors and links) on the system throughput. The results we have obtained demonstrate the impact of different reliability and availability models on the system throughput. [ABSTRACT FROM AUTHOR]

The article reports on the development of a foundation for autonomic workflow management in a grid environment. A model for dynamic fault tolerance technique selection was developed. This can be embedded into the workflow management system for a mobile agent. Current architecture for flexible fault tolerance in the grid was then augmented in order to allow the system to optimally configure its fault tolerant systems through an awareness of the computing environment.

Abstract: A wide range of algorithms have been developed for various types of negotiating agents. In developing such algorithms the main focus has been on their efficiency and their effectiveness. However, this is only a part of the picture. Typically, agents negotiate on behalf of their owners and for this to be effective the agents must be able to adequately represent their owners’ strategies and preferences for negotiation. However, the process by which such knowledge is acquired is typically left unspecified. To address this problem, we undertook a study of how user information about negotiation tradeoff strategies and preferences can be captured. Specifically, we devised a novel default-then-adjust acquisition technique. In this, the system firstly does a structured interview with the user to suggest the attributes that the tradeoff could be made between, then it asks the user to adjust the suggested default tradeoff strategy by improving some attribute to see how much worse the attribute being traded off can be made while still being acceptable, and, finally, it asks the user to adjust the default preference on the tradeoff alternatives. This method is consistent with the principles of standard negotiation theory and to demonstrate its effectiveness we implemented a prototype system and performed an empirical evaluation in an accommodation renting scenario. The result of this evaluation indicates the proposed technique is helpful and efficient in accurately acquiring the users’ tradeoff strategies and preferences. [Copyright &y& Elsevier]

Abstract: This paper proposes a framework for a multiplatform mobile agent system based on Web services. The framework includes a mobile agent factory, the mobile agents, and the host Web services. The mobile agents are created at the factory, migrate between Web services-enabled hosts, and execute at the destination hosts through invocation by XML-RPC. The transfer of mobile agents is accomplished through the employment of SOAP attachments where service handlers are used at the source and destination hosts to attach and detach agent files, respectively. The framework was implemented using the Java Web Service Developer Pack (JWSDP) and tested on 20 Linux and Windows hosts within a Wide Area Network (WAN). The system worked seamlessly on all designated hosts (proving interoperability) while comparing well in terms of throughput to three well-known mobile agent systems, namely, Voyager, Aglets, and Concordia. This paper demonstrates how the proposed system can interoperate with existing systems and serve as a model for interoperability among them. The paper also illustrates how the mobile agent can be secured against confidentiality and integrity attacks during transport and suggests ways for protecting it from malicious hosts as well as guarding hosts from malicious agents. [Copyright &y& Elsevier]

We develop a semantics theory for SAP, a variant of Levi and Sangiorgi's Safe Ambients, SA. The dynamics of SA relies upon capabilities (and co-capabilities) exercised by mobile agents, called ambients, to interact with each other. These capabilities contain references, the names of ambients with which they wish to interact. In SAP we generalize the notion of capability: in order to interact with an ambient n, an ambient m must exercise a capability indicating both n and a password h to access n; the interaction between n and m takes place only if n is willing to perform a corresponding co-capability with the same password h. The name h can also be looked upon as a port to access ambient n via port h. In SAP, by managing passwords/ports, for example generating new ones and distributing them selectively, an ambient may now program who may migrate into its computation space, and when. Moreover in SAP, an ambient may provide different services/resources depending on the port accessed by the incoming clients. Then we give an Its-based operational semantics for SAP and a labelled bisimulation equivalence, which is proved to coincide with reduction barbed congruence. We use our notion of bisimulation to prove a set of algebraic laws that are subsequently exploited to prove more significant examples. [ABSTRACT FROM AUTHOR]

This paper presents a framework for reusable mobile agents for network management in the sense that they are independent of either particular networks or applications. The framework enables a mobile agent to be composed from two layered components, which are mobile agents. The former is a carrier of the latter over particular networks independent of any management tasks and the latter defines management tasks performed at each host independently of any networks. The framework also oilers a mechanism for matchmaking the two components. Since the mechanism is formulated on a process algebra approach, it can accurately select the appropriate itinerary component to perform management tasks at hosts that the tasks want to visit over networks. The framework provides a methodology for easily developing and operating mobile agents for traveling among multiple sub-networks to perform their management tasks at all of the nodes that they visit. This paper also describes the framework, its prototype implementation, and a practical application. [ABSTRACT FROM AUTHOR]

In open societies of agents, where agents are autonomous and heterogeneous, it is not realistic to assume that agents will always act so as to comply with interaction protocols. Thus, the need arises for a formalism to specify constraints on agent interaction, and for a tool able to observe and check for agent compliance with interaction protocols. In this paper we present a JAVA-PROLOG software component built on logic programming technology, which can be used to verify compliance of agent interaction to protocols, and that has been integrated with the PROSOCS platform. [ABSTRACT FROM AUTHOR]

PROSOCS agents are software agents that are built according to the KGP model of agency. KGP is used as a model for the mind of the agent, so that the agent can act autonomously using a collection of logic theories, providing the mind's reasoning functionalities. The behavior of the agent is controlled by a cycle theory that specifies the agent's preferred patterns of operation. The implementation of the mind's generic functionality in PROSOCS is worked out in such a way so it can be instantiated by the platform for different agents across applications. In this context, the development of a concrete example illustrates how an agent developer might program the generic functionality of the mind for a simple application. [ABSTRACT FROM AUTHOR]

The paper introduces some issues and related solutions adopted in order to realize the MMASS platform. This is a framework to specify and execute simulation applications based on the multi-layered multi-agent situated system model (MMASS). MMASS is a model for multi-agent systems (MAS) situated in an environment whose structure is explicitly defined. The behavior and interaction models of MMASS agents are strongly related to the spatial structure of their environment. The MMASS model is the result of a long-term research that has its roots and motivations on application domains and problems that require spatial features to be considered. Our experiences with these problems have concerned the design of domain models and their implementations, according to the MAS approach for simulation purposes. This activity has revealed that currently available tools do not support the management of spatial features of agent environment and interaction mechanisms defined by the MMASS model and thus they are not suitable for our purposes. The paper focuses on the MMASS platform that aims to support the specification and development of applications (mainly, simulations) based on MMASS. Design issues and related solutions that have been adopted in order to manage those aspects that characterize the MMASS model will be shown. After a description of the conceptual model that underlies the MMASS platform and its general architecture, we will overview how the platform supports the specification of agent structured environment, behavior and interaction, and how it supports the execution of agent actions and interactions. Then we will describe issues and adopted solutions (both algorithmic and implementative ones) to manage at-a-distance interaction among MMASS agents. [ABSTRACT FROM AUTHOR]

Enabling and managing coordination activities between autonomous, possibly mobile, computing entities in dynamic computing scenarios challenges traditional approaches to distributed application development and software engineering. This paper specifically focuses on the problem of motion coordination, and proposes field-based coordination as a general framework to model and engineer such coordinated behaviors. The key idea in field-based coordination is to have agents' movements driven by computational force fields, generated by the agents themselves and/or by some infrastructure, and propagated across the environment. This paper shows that field-based approaches enable the definition of adaptive and effective motion coordination schemes, which can be modeled and tested by making use of a dynamical systems formalism, and which can be easily implemented either above existing middleware infrastructures or by making use of novel middleware specifically conceived for field-based coordination. [ABSTRACT FROM AUTHOR]

The evolution of powerful portable networked devices allows nomadic users seamless access to business and leisure information any time and any where. This drives service infrastructures to similarly evolve to meet new service management challenges in order to adapt information delivery to a richer spatial, temporal, and user context whilst balancing the concerns of the different stakeholders. This paper presents the use of a multi-agent system service infrastructure and associated privacy model to maintain the balance between the service provider's need to maximize its knowledge of the user context against the need for the user's privacy to be protected. [ABSTRACT FROM AUTHOR]