On using the CAMA framework for developing open mobile fault tolerant agent systems

The paper introduces the Cama (Context-Aware Mobile Agents) framework intended for developing large-scale mobile applications using the agent paradigm. Cama provides a powerful set of abstractions, a supporting middleware and an adaptation layer allowing developers to address the main characteristics of the mobile applications: openness, asynchronous and anonymous communication, fault tolerance, device mobility. It ensures recursive system structuring using location, scope, agent and role abstractions. Cama supports system fault tolerance through exception handling and structured agent coordination. The applicability of the framework is demonstrated using an ambient lecture scenario - the first part of an ongoing work on a series of ambient campus applications

On developing open mobile fault tolerant agent systems

The paper introduces the CAMA (Context-Aware Mobile Agents) framework intended for developing large-scale mobile applications using the agent paradigm. CAMA provides a powerful set of abstractions, a supporting middleware and an adaptation layer allowing developers to address the main characteristics of the mobile applications: openness, asynchronous and anonymous communication, fault tolerance, and device mobility. It ensures recursive system structuring using location, scope, agent, and role abstractions. CAMA supports system fault tolerance through exception handling and structured agent coordination within nested scopes. The applicability of the framework is demonstrated using an ambient lecture scenario - the first part of an ongoing work on a series of ambient campus applications. This scenario is developed starting from a thorough definition of the traceable requirements including the fault tolerance requirements. This is followed by the design phase at which the CAMA abstractions are applied. At the implementation phase, the CAMA middleware services are used through a provided API. This work is part of the FP6 IST RODIN project on Rigorous Open Development Environment for Complex Systems

Using mobility and exception handling to achieve mobile agents that survive server crash failures

Mobile agent technology, when designed and used effectively, can minimize bandwidth consumption and autonomously provide a snapshot of the current context of a distributed system. Protecting mobile agents from server crashes is a challenging issue, since developers normally have no control over remote servers. Server crash failures can leave replicas, instable storage, unavailable for an unknown time period. Furthermore, few systems have considered the need for using a fault tolerant protocol among a group of collaborating mobile agents. This thesis uses exception handling to protect mobile agents from server crash failures. An exception model is proposed for mobile agents and two exception handler designs are investigated. The first exists at the server that created the mobile agent and uses a timeout mechanism. The second, the mobile shadow scheme, migrates with the mobile agent and operates at the previous server visited by the mobile agent. A case study application has been developed to compare the performance of the two exception handler designs. Performance results demonstrate that although the second design is slower it offers the smaller trip time when handling a server crash. Furthermore, no modification of the server environment is necessary. This thesis shows that the mobile shadow exception handling scheme reduces complexity for a group of mobile agents to survive server crashes. The scheme deploys a replica that monitors the server occupied by the master, at each stage of the itinerary. The replica exists at the previous server visited in the itinerary. Consequently, each group member is a single fault tolerant entity with respect to server crash failures. Other schemes introduce greater complexity and performance overheads since, for each stage of the itinerary, a group of replicas is sent to servers that offer an equivalent service. In addition, future research is established for fault tolerance in groups of collaborating mobile agents

An approach to rollback recovery of collaborating mobile agents

Fault-tolerance is one of the main problems that must be resolved to improve the adoption of the agents' computing paradigm. In this paper, we analyse the execution model of agent platforms and the significance of the faults affecting their constituent components on the reliable execution of agent-based applications, in order to develop a pragmatic framework for agent systems fault-tolerance. The developed framework deploys a communication-pairs independent check pointing strategy to offer a low-cost, application-transparent model for reliable agent- based computing that covers all possible faults that might invalidate reliable agent execution, migration and communication and maintains the exactly-one execution property

Investigation into Mobile Learning Framework in Cloud Computing Platform

Abstract—Cloud computing infrastructure is increasingly used for distributed applications. Mobile learning applications deployed in the cloud are a new research direction. The applications require specific development approaches for effective and reliable communication. This paper proposes an interdisciplinary approach for design and development of mobile applications in the cloud. The approach includes front service toolkit and backend service toolkit. The front service toolkit packages data and sends it to a backend deployed in a cloud computing platform. The backend service toolkit manages rules and workflow, and then transmits required results to the front service toolkit. To further show feasibility of the approach, the paper introduces a case study and shows its performance

On rigorous design and implementation of fault tolerant ambient systems

Developing fault tolerant ambient systems requires many challenging factors to be considered due to the nature of such systems, which tend to contain a lot of mobile elements that change their behaviour depending on the surrounding environment, as well as the possibility of their disconnection and re-connection. It is therefore necessary to construct the critical parts of fault tolerant ambient systems in a rigorous manner. This can be achieved by deploying formal approach at the design stage, coupled with sound framework and support at the implementation stage. In this paper, we briefly describe a middleware that we developed to provide system structuring through the concepts of roles, agents, locations and scopes, making it easier for the developers to achieve fault tolerance. We then outline our experience in developing an ambient lecture system using the combination of formal approach and our middleware

Prototype of Fault Adaptive Embedded Software for Large-Scale Real-Time Systems

This paper describes a comprehensive prototype of large-scale fault adaptive embedded software developed for the proposed Fermilab BTeV high energy physics experiment. Lightweight self-optimizing agents embedded within Level 1 of the prototype are responsible for proactive and reactive monitoring and mitigation based on specified layers of competence. The agents are self-protecting, detecting cascading failures using a distributed approach. Adaptive, reconfigurable, and mobile objects for reliablility are designed to be self-configuring to adapt automatically to dynamically changing environments. These objects provide a self-healing layer with the ability to discover, diagnose, and react to discontinuities in real-time processing. A generic modeling environment was developed to facilitate design and implementation of hardware resource specifications, application data flow, and failure mitigation strategies. Level 1 of the planned BTeV trigger system alone will consist of 2500 DSPs, so the number of components and intractable fault scenarios involved make it impossible to design an `expert system' that applies traditional centralized mitigative strategies based on rules capturing every possible system state. Instead, a distributed reactive approach is implemented using the tools and methodologies developed by the Real-Time Embedded Systems group.Comment: 2nd Workshop on Engineering of Autonomic Systems (EASe), in the 12th Annual IEEE International Conference and Workshop on the Engineering of Computer Based Systems (ECBS), Washington, DC, April, 200

Goal accomplishment tracking for automatic supervision of plan execution

It is common practice to break down plans into a series of goals or sub-goals in order to facilitate plan execution, thereby only burdening the individual agents responsible for their execution with small, easily achievable objectives at any one time, or providing a simple way of sharing these objectives amongst a group of these agents. Ensuring that plans are executed correctly is an essential part of any team management. To allow proper tracking of an agent's progress through a pre-planned set of goals, it is imperative to keep track of which of these goals have already been accomplished. This centralised approach is essential when the agent is part of a team of humans and/or robots, and goal accomplishment is not always being tracked at a low level. This paper presents a framework for an automated supervision system to keep track of changes in world states so as to chart progress through a pre-planned set of goals. An implementation of this framework on a mobile service robot is presented, and applied in an experiment which demonstrates its feasibility

A comparison of mechanisms for locating mobile agents

In this paper we present different possible approaches for locating mobile agents and introduce a classification for them. We will use this classification to categorize mechanisms proposed in standards and implemented in mobile agent systems. Then we assess the different mechanisms regarding their fault tolerance, their message complexity and the migration delay they induce. We conclude by combining the different assessments to allow a comparison of all mechanisms