Research On Key Issues Of Mobile Agent System

Mobile agent provides a novel paradigm for distributed computing. It has the potential to offer a single, general framework in which a wide range of distributed systems can be implemented efficiently, easily and robustly. Nevertheless, mobile agent technology is in a fairly early state. To make mobile agents attractive in as wide a range of applications as possible, a number of problems need. This dissertation mainly focuses on these problems and addresses three key issues of mobile 'agent system: communication mechanism, itinerary planning and coalition strategy. The main contributions of this dissertation are as follows:(1) A Mobile Agent Development Platform (MADP) is constructed based on the advanced characteristics of Java. In the system architecture of MADP, the bottom layer is composed of TCP/IP protocol, operating system and Java virtual machine. The core layer of the system, AgentHost layer, consists of agent manager, security service, communication service, migration service, event service and resource management. AgentHost provides a secure and smooth supporting environment for mobile agents. The agent layer, which is made up of those mobile agents developed by users, performs distributed computing assigned by their owners. The development of MADP conforms to the object-oriented principle. This makes the MADP system open enough for importing modules to enhance intelligence and security. The system is highly robust and flexible. It is very easy for users to develop their own distributed computing task using MADP.(2) This dissertation proposes DCC, an efficient message delivery mechanism for mobile agent system. The DCC mechanism separates the network into several domains. Hosts, mobile agents and communication and mediation server cooperate with each other to implement the communication among agents. Whatever status the target agent is in, it could receive messages. So it solves the intermittent connection problem of mobile devices successfully. To remove the bottleneck caused by centralized control, we introduce the concept of agent current location cache and define four notification messages about cache information. It eases the burden of communication and mediation server and shortens the transmission delay of message delivery. This method improves the communication efficiency and guarantees the robustness and scalability of mobile agent system.(3) An improved ant colony algorithm is presented in this dissertation. A mutation operator is introduced and global updating rule is modified on the basis of ant colony system. Ants could achieve the goal of cooperation by indirect communication mediated by pheromone and find goodIIIsolutions to , their task guided by the tradeoff between exploitation and exploration. The probability of premature convergence is low due to the introduction of genetic operator and modification of global updating rule. The traveling agent problem is solved using improved ant colony algorithm and promising result is obtained. Experimental results show that improved ant colony algorithm exhibits some excellent characteristics of robustness, self-adaptation, parallelism and positive feedback. So mobile agents could accomplish their distributed computing task with high efficiency and short time. (4) A coalition mechanism for mobile agent system is presented based on genetic algorithm. As an important coordination and cooperation mechanism in mobile agent system, agent coalition exhibits some excellent characteristics and receives attention increasingly. An efficient algorithm is needed for this topic since the number of the possible coalitions is exponential. Genetic Algorithm has been widely reckoned as a useful tool for obtaining high quality or even optimal solutions for a broad range of combinatorial optimization problems due to its intelligent advantages of self-organization, self-adaptation and inherent parallelism. This dissertation proposes a GA-based algorithm with an objective to simultaneously meet the goals of high performance, scalability, and fast run...