Narrow Results

Traditional message passing based checkpointing and rollback recovery algorithms perform well for tightly coupled systems. In wide area distributed systems these algorithms may suffer from large overhead due to message passing delay and network traffic. Mobile agents offer an attractive option for designing checkpointing schemes for wide area distributed systems. Network topology is assumed to be arbitrary. Processes are mobile agent enabled. When a process wants to take a checkpoint, it just creates one mobile agent. Concurrent initiations by multiple processes are allowed. Synchronization and creation of a consistent global state (CGS) for checkpointing is managed by the mobile agent(s). In the worst case, for k concurrent initiations among n processes, checkpointing algorithm requires a total of O(kn) hops by all the mobile agents. A mobile agent carries O(n/k) (on the average) size data.

A black hole in a network is a highly harmful host that disposes of any incoming agents upon their arrival. Determining the location of a black hole in a ring network has been studied when each node is equipped with a whiteboard. Recently, the Black Hole Search problem was solved in a less demanding and less expensive token model with co-located agents. Whether the problem can be solved with scattered agents in a token model remains an open problem.

In this paper, we show not only that a black hole can be located in a ring using tokens with scattered agents, but also that the problem is solvable even if the ring is un-oriented. More precisely, first we prove that the black hole search problem can be solved using only three scattered agents. We then show that, with K (K ⩾ 4) scattered agents, the black hole can be located in O(kn + n log n) moves. Moreover, when K (K ⩾ K) is a constant number, the move cost can be reduced to O(n log n), which is optimal. These results hold even if both agents and nodes are anonymous.

A mobile agent starting at an arbitrary node of an m × k grid, for 1 < m ≤ k, has to explore the grid by visiting all its nodes and traversing all edges. The cost of an exploration algorithm is the number of edge traversals by the agent. Nodes of the grid are unlabeled and ports at each node v have distinct numbers in {0,…, d − 1}, where d = 2, 3, 4 is the degree of v. Port numbering is local, i.e., there is no relation between port numbers at different nodes. When visiting a node the agent sees its degree. It also sees the port number by which it enters a node and can choose the port number by which it leaves a visited node. We are interested in deterministic exploration algorithms working at low cost.

We consider the scenario in which the agent is equipped with a stationary token situated at its starting node. The agent sees the token whenever it visits this node. We give an exploration algorithm working at cost O(k²) for 2 × k grids, and at cost O(m²k), for m × k grids, when 2 < m ≤ k.

We consider the problem of exploration of networks, some of whose edges are faulty. A mobile agent, situated at a starting node and unaware of which edges are faulty, has to explore the connected fault-free component of this node by visiting all of its nodes. The cost of the exploration is the number of edge traversals. For a given network and given starting node, the overhead of an exploration algorithm is the worst-case ratio (taken over all fault configurations) of its cost to the cost of an optimal algorithm which knows where faults are situated. An exploration algorithm, for a given network and given starting node, is called perfectly competitive if its overhead is the smallest among all exploration algorithms not knowing the location of faults. We design a perfectly competitive exploration algorithm for any ring, and show that, for networks modeled by hamiltonian graphs, the overhead of any DFS exploration is at most 10/9 times larger than that of a perfectly competitive algorithm. Moreover, for hamiltonian graphs of size at least 24, this overhead is less than 6% larger than that of a perfectly competitive algorithm.

In the world of mobile agents, security aspects are being discussed extensively, with strong emphasis on how agents can be protected against malicious hosts and vice versa. While in recent years many research groups presented solutions offering protection schemes for hosts that receive and run un-trusted, possibly malicious agents, in the field of protecting the agent against malicious hosts, development seems to grow very slowly. This paper discusses a protocol for detecting modifications at the agent's binary code that, for a particular class of modifications, undoubtedly unmasks the attacking host. Furthermore, it is shown that in co-operation with a special kind of route protection in a lot of scenarios the protocol resists attacks from coaliting malicious hosts as well as from a single malicious host.

Security modeling for agents has been one of the most challenging issues in developing practical mobile agent software systems. In the past, researchers have developed mobile agent systems with emphasis either on protecting mobile agents from malicious hosts or protecting hosts from malicious agents. In this paper, we propose a security based mobile agent system architecture that provides a general solution to protecting both mobile agents and agent hosts in terms of agent communication and agent migration. We present a facilitator agent model that serves as a middleware for secure agent communication and agent migration. The facilitator agent model, as well as the mobile agent model, is based on agent-oriented G-nets — a high level Petri net formalism. To illustrate our formal modeling technique for mobile agent systems, we provide an example of agent migration to show how a design error can be detected.

Mobile agent paradigm is recognized as a new environment for distributed computing and provides many merits such as mobility, security, self-decision, and so on. However, its security problems should be resolved to increase its application to a variety of real domains. Especially, we must guarantee integrity of transferred mobile agents. Although many mobile agent systems were developed, the integrity issue remains a critical one. In this paper, we propose an integrity checking mechanism to do the aforementioned issue. The proposed mechanism is independent of specific security frameworks and can be added and used easily for various mobile agent platforms.

A lot of schemes have been proposed for the establishment of u-city. Especially, most of the schemes are based on ubiquitous networks. In this paper, it is assumed that the ubiquitous networks include some mobile agents. Therefore, an intelligent positioning scheme is proposed for the efficient positioning of the mobile agents in the ubiquitous networks. The approach consists of location detection and location tracking. Furthermore, an optimal diversity technique is presented in this paper to improve the positioning performance. Simulation results indicate that using the suggested algorithms, the excellent detection and tracking performance can be achieved in ubiquitous networks for u-city.

The data warehouse (DWH) is usually presented as a centralized database. In this paper, we propose a new approach to manage data storage and distribution in a data warehouse environment. This approach deals with the dynamic data distribution of the DWH on a set of servers. The data distribution that we consider is different from the "classical" one which depends on the data use. The distribution in our approach consists in distributing data when the server reaches its storage capacity limit. This distribution assures the scalability and exploits the storage and processing resources available in the organization using the data warehouse. It is worth noting that our approach is based on a multi-agent model mixed with the scalability distribution proposed by the Scalable Distributed Data Structures.

The proposed multi-agent model is composed of stationary agent classes: Client, Dispatcher, Domain and Server, and a mobile agent class called Messenger. These agents collaborate and interact to achieve automatically the storage, the splitting (distribution), the redirection and the access operations on the distributed data warehouse.

In this paper, we demonstrate the improvements obtained when we have used the multi-agent system and the Messenger agents in the data storage operation.

Recently, semantic web has received substantial attention from the research community. Semantic web aims to provide a new framework that can enable knowledge sharing and reusing. Semantic web is a collection of web technologies that include a number of markup languages such as RDF, OWL and RDFS. These markup languages are used for modeling a domain ontology. By using ontology to model resources, humans and computers (software agents) can have a consensus on the resource structure. The use of these technologies allows the creation of a more effective web search system. In this paper, we modeled travel domain ontology by using Web Ontology Language (OWL). Instead of inviting an expert to model the ontology, we created the travel ontology by collecting and analyzing the structural information from a number of travel related websites. Besides, we implemented an intelligent ontology-based Multi-Agent System for sighTseER (MASTER), which is constructed by using semantic web technologies. MASTER integrates Global Positioning System (GPS), ontology and agent technologies to support location awareness for providing the precise navigation and classify the tourist information for the users. The system was tested on 30 novice users. 83% of the users felt that the system can help tourists find tourist information in Hong Kong.

The emergence of mobile computing environments brings out various changes in the requirements and applications involving distributed data and has made the traditional Intelligent Decision Support System (IDSS) architectures based on the client/server model ineffective in mobile computing environments. This paper discusses the deficiencies of the current IDSS architectures based on data warehouse, on-line analysis processing (OLAP), model base (MB) and knowledge based (KB) technologies. By adopting the agent technology, the paper extends the IDSS system architecture to the Mobile Decision Support System (MDSS) architecture. The logical structure and the application architecture of the MDSS and the mechanisms and implementation strategies of the User Access Agent System, a major component of the MDSS, are described in this paper.

The traditional client/server-based distributed system design paradigm demonstrates deficiencies in the mobile computing environment because it relies on network connectivity and reliable communication. The advances in mobile agent technology alleviate these problems. The execution autonomy of mobile agents relaxes the requirement on network connectivity and provides opportunities for conserving energy. To the best of our knowledge, in spite of the large body of research in the application and exploitation of agent-based technology, a quantitative comparison of systems implemented using the client/server and agent-based models is still missing and issues related to the energy efficiency of mobile agents remain unexplored. In this paper, we present a quantitative performance evaluation of these two models in terms of response time, energy consumption, and communication cost.

A mobile agent (robot) has to explore an unknown terrain modeled as a planar embedding of an undirected planar connected graph. Exploration consists in visiting all nodes and traversing all edges of the graph, and should be completed using as few edge traversals as possible. The agent has an unlabeled map of the terrain which is another planar embedding of the same graph, preserving the clockwise order of neighbors at each node. The starting node of the agent is marked in the map but the map is unoriented: the agent does not know which direction in the map corresponds to which direction in the terrain. The quality of an exploration algorithm is measured by comparing its cost (number of edge traversals) to that of the optimal algorithm having full knowledge of the graph. The ratio between these costs, for a given input consisting of a graph and a starting node, is called the overhead of algorithm for this input. We seek exploration algorithms with small overhead. We show an exploration algorithm with overhead of at most 7/5 for all trees, which is the best possible overhead for some trees. We also show an exploration algorithm with the best possible overhead, for any tree with starting node of degree 2. For a large class of planar graphs, called stars of graphs, we show an exploration algorithm with overhead of at most 3/2. Finally, we show a lower bound 5/3 on the overhead of exploration algorithms for some planar graphs.

This work designs, develops and implements a virtual laboratory for digital circuit design in Macro Universities that can create a rich learning environment for students from all over the world. Our system consists of four parts: agent execution environments, mobile agents, wrapper agents and experimental platforms. Mobile agents are received and executed in the agent execution environment, which provides locations and other resources for the mobile agents. The wrapper agent acts as a middleware for the mobile agent and the experimental platform. The experimental platform is an existing application program that could be a learning program, such as a CAI tool or a design tool, such as a CAD system. The major merit of our system is that it enables network capability for a standalone program without the need for the source code of the original program. The prototype of our virtual laboratory is targeted at a digital circuit laboratory. Experimental results demonstrate the feasibility of our approach.

Collaborative Virtual Environment (CVE) is a promising technology which provides an online shared virtual world to the geographically dispersed people to interact with each other. However, the scalability of existing CVE system is limited due to the constraints in processing power and network speed of each participating host. Large scale CVE (LCVE) that supports a large number of concurrent participants and a large amount of evolving virtual entities is not easy to achieve. In this paper, an autonomous decentralized grid based mobile agent framework for large scale CVE — MACVE is proposed. In MACVE, LCVE software system is decomposed into a group of collaborative mobile agents, each of which is responsible for an independent system task. Agents can migrate or clone dynamically at any suitable participating host (grid node) include traditional servers and qualified user hosts to avoid bottleneck, which can improve the scalability of LCVE. Therefore, MACVE is a logically multi-server architecture while the server workload is autonomously decentralized. Our system prototype and evaluation has demonstrated the feasibility of the proposed framework.

The Internet has brought about innumerable changes to the way enterprises do business. An essential problem to be solved before the widespread commercial use of the Internet is to provide a trustworthy solution for electronic payment. We propose a multi-agent mediated electronic payment architecture in this paper. It is aimed at providing an agent-based approach to accommodate multiple e-payment schemes. Through a layered design of the payment structure and a well-defined uniform payment interface, the architecture shows good scalability. When a new e-payment scheme or implementation is available, it can be plugged into the framework easily. In addition, we construct a framework allowing multiple agents to work cooperatively to realize automation of electronic payment. A prototype has been built to illustrate the functionality of this design. Finally, we discuss the security issues.

The long use of a system causes its degradation. Hence, the maintenance activity is required in order to keep and improve the efficiency in the system. With the rapid development in networking technology, a need appears to change the manufacturing strategies. These new technologies improve the maintenance process, and establish remote maintenance (tele-maintenance, e-maintenance and m-maintenance). These kinds of maintenance try to provide personnel maintenance with the right information at the suitable time, which makes information available, anywhere and anytime. Our proposition is the use of mobile agent technology to reduce the maintenance costs and solve the problem of the unavailability of an expert in all phases of condition-based maintenance (CBM) strategy. The mobile agent technology overcomes a lot of problems and there is not much work that has used this technology. We have also used the web services (WS) to insure interoperability between machines and to support interaction over the network. Our approach gives great support to the maintenance engineer as it facilitates the access to decision-making support, work order, etc. which are available in the device like smartphone. This paper presents the development of a mobile maintenance support system based on mobile agent technology. The proposed system, the web and agent technology as well as remote communication were tested successfully.

In this paper, we propose an evacuation support system that provides evacuation routes in case of disasters, and verify the usefulness of the system. Current popular wireless communication infrastructure is supported by a series of base stations and one base station handles a lot of communication. Therefore, when communication base stations break down due to disasters such as an earthquake, it may become difficult for people to use their smartphones based on the Internet. When the communication infrastructure is paralyzed, people will have great difficulty collecting information about the conditions of transportation systems and about the safety of family and friends using smartphones. Our proposed system addresses this problem by using multiple kinds of mobile agents in addition to static agents on smartphones that use a mobile ad hoc network (MANET). The proposed system collects information with mobile agents and diffuses information via mobile agents so that the system is able to provide an optimized evacuation route for each user in a dynamically changing disaster environment. In this paper, we extend our previously proposed evacuation support system to consider elevation information when constructing evacuation routes. When a tsunami or a flood tide occurs, low elevations may be under water. Therefore, this revised evacuation support system helps people to move to safer places by selecting higher elevation routes when warranted by the situation.

In this paper, we propose an algorithm for controlling a fleet of swarm robots that construct three-dimensional forms. The swarm robots coordinate with each other through network communication, and compose formations such as polyhedrons presented as spherical coordinates. Our control algorithm achieves communication through mobile software agents, which introduce control programs to robots that initially have no information about the formation. Mobile software agents are autonomous objects that can migrate from one robot to other robots through a communication network and can deliver control programs as they are needed. We have made our swarm robot system to mimic the behaviors of the leafcutter ants. A leafcutter ant is a typical social insect and uses pheromone for communication. In our robot control system, we have implemented ants and pheromones as mobile software agents. We call the mobile software agents that drive the mobile robots as ant agents, and call the other agents that provide communication as pheromone agents. The ant agents drive the swarm robots to locations identified by the pheromone agents. Each ant agent has only partial information. There is no need for either a central control or an agent that has the entire design of the formation. In order to diffuse the partial information among the neighboring robots, each ant agent generates pheromone agents and dispatches them to the surrounding robots. Dispatched pheromone agent looks for a proper ant agent to influence towards a desired relative location. It is the ant agent that actually drives the robot by following the guidance of the pheromone agent, and the collective actions of ant agents and pheromone agents achieve the composition of the objective formation. We have implemented a simulator based on our algorithm and conducted numerical experiments. The results demonstrate that our mobile robot control system is feasible and efficient in practice in practical situations.

Active network provides a programmable interface to the user where users dynamically inject services into the intermediate nodes. This paper discussed the issue, which in the tradition network management exists, and has analyzed the active network management system structure and the management mechanism. The paper propose a mobile agent management mechanism based on active network, and analyze this network management system structure, and study emphasis on the system structure, the management mechanism, the management strategy.