Duncan Russell

Efficient and scalable search on scale-free P2P networks

Unstructured peer-to-peer (P2P) systems (e.g. Gnutella) are characterized by uneven distributions of node connectivity and file sharing. The existence of “hub” nodes that have a large number of connections and “generous” nodes that share many files significantly influences performance of information search over P2P file-sharing networks. In this paper, we present a novel Scalable Peer-to-Peer Search (SP2PS) method with low maintenance overhead for resource discovery in scale-free P2P networks. Different from existing search methods which employ one heuristic to direct searches, SP2PS achieves better performance by considering both of the number of shared files and the connectivity of each neighbouring node. SP2PS enables peer nodes to forward queries to the neighbours that are more likely to have the requested files and also can help in finding the requested files in the future hops. The proposed method has been simulated in different power-law networks with different forwarding degrees and distances. From our analytic and simulation results, SP2PS achieves better performance when compared to other related methods.

Delivering Sustainable Capability on Evolutionary Service-oriented Architecture

Network Enabled Capability (NEC) is the U.K. Ministry of Defence’s response to the quickly changing conflict environment in which its forces must operate. In NEC, systems need to be integrated in context, to assist in human activity and provide dependable inter-operation. In order to provide reliable and sustainable military capability, fast paced changes must be conducted without halting the operation of a capability. In this paper we present the concept of evolutionary service-oriented architecture for delivering sustainable capability. The reliability of the architecture is evaluated by simulations using a computer-based model. The simulation results indicate that the evolutionary service-oriented architecture can provide higher reliability and sustainability in the provision of capability in a dynamic environment.

Service-based collaborative workflow for DAME

The paper reports on research to design and implement a service-based, secure collaborative workflow system for distributed aircraft maintenance environment (DAME). This has been developed by the Universities of York, Sheffield, Oxford and Leeds, and industrial partners, Rolls-Royce and Data Systems and Solutions (DS&S). DAME is a prototype system to support aircraft engine maintenance and predictive services. It is an example of a virtual organisation with grid-based services running at the four universities sites. To meet the industrial requirements strong security is implemented to protect commercially sensitive services and data. Application services have been coordinated using the DAME workflow management system to automate business processes and control collaborative access. A dynamic workflow-team policy is used to authorise user access to workflow instances and corresponding service instances. The paper includes aspects of an initial evaluation with the industrial participants and illustrates the feasibility of using DAME in an industrial environment.

Modelling and simulation of Network Enabled Capability on service-oriented architecture

Network Enabled Capability (NEC) is the UK Ministry of Defence’s response to the quickly changing conflict environment in which its forces must operate. In NEC, systems need to be integrated in context, to assist in human activity and provide dependable inter-operation. In this paper, we present our research work in the NECTISE project with a focus on the modelling and simulation of service-oriented architecture (SOA) for delivering dependable and sustainable military capability. The simulation results indicate that the proposed architectural model can provide a high-level of reliability and sustainability in the provision of capability in a dynamic environment. Moreover, a NEC demonstration system for regional surveillance is introduced in this paper to illustrate the use of SOA to achieve NEC.

Self-Organization of Autonomous Peers with Human Strategies

Similarly to social networks where people are connected by their social relationships, two autonomous peer nodes can be connected in unstructured peer-to-peer (P2P) networks if users in those nodes are interested in each others data. The similarity between P2P networks and social networks, where peer nodes are people and connections are relationships, leads us to believe that human strategies in social networks are useful for improving the performance of resource discovery by self-organising autonomous peers on unstructured P2P networks. In this paper, we present an efficient social-like peer-to-peer (ESLP) model for resource discovery by mimicking different human behaviours in social networks.

Migrating Legacy Assets through SOA to Realize Network Enabled Capability

Network Enabled Capability (NEC) is the UK Ministry of Defence’s aspiration to enhance the achievement of military effect through the networking of future and existing military capabilities. The NECTISE (NEC Through Innovative Systems Engineering) program responded to this need by investigating the question ‘are you ready for NEC?’ on behalf of equipment and service providers. Research work on this project proposed Service Oriented Architectures (SOA) as an architectural approach to delivering dependable and sustainable military capability. Specifically the work looked at how loosely coupled services could be used to expose and reuse functions and databases and how to describe the quality of service for heterogeneous systems and networks. The System of Systems that NEC will be realized from will not be implemented from scratch, but rather will be migrated from legacy assets over time. These assets will provide both functionality and data/information services, for example a weather sensor.

A secure service-based collaborative workflow system

This paper addresses a need to control collaborative access to shared web service resources (grid services) in workflows. The workflows are executed by users from different organisations who act in roles in a business process. These workflows execute services across organisations, which create service instances that can be accessed by different users during the workflow lifetime. Controlling collaborative access to service instances is difficult when the users are from distributed organisations and the access changes during the service instance lifetime. Current access control techniques provide constraints for users mapped to roles and the roles assigned to tasks. However, we extend this by proposing a framework to include collaborative access to service instances. These service instances execute workflow tasks and are temporary assets for collaborative use. The Distributed Aircraft Maintenance Environment (DAME) project is used to demonstrate a collaborative portal and Workflow Management System (WFMS) in which teams of users from different organisations share grid service instances. After evaluation, the resulting proposed solution uses a dynamic Workflow Team Policy to maintain users in roles and record service instances as temporal business assets.

Dynamic service integration for reliable and sustainable capability provision

The move towards network enabled capability (NEC) by the UK Ministry of Defence is designed to achieve enhanced military effect through the networking and coherent integration of existing and future resources including sensors, weapon systems and decision-makers to achieve a more flexible and responsive military. This article addresses the existing reliability and sustainability issues of large-scale military systems and proposes new architectural approaches of dynamic service integration for NEC to adapt to evolution occurring in services and capability for constructing next-generation software-intensive military systems. The reliability and performance of the proposed architectural approaches have been verified through modelling and simulation of service-oriented architecture for NEC and demonstrated through developing and testing a NEC system for a region surveillance capability scenario. The experimental results indicate that the proposed architectural approaches provide a high level of reliability and sustainability in the provision of NEC.

Scenario-based design and evaluation for capability

Scenarios are frequently used within techniques for planning and designing systems. They are an especially helpful means of visualizing and understanding the incorporation of new systems within systems of systems. If used as the basis for decisions about candidate designs, then it is important that such decisions can be rationalized and quantitative assessment is particularly important. In this paper, an approach for developing complex scenarios, which incorporates the phases of systems development and deployment, is presented and a quantitative method of comparison is described. This approach is based on the development of measures of merit and measures of performance. The techniques are illustrated using cases that are relevant to Network Enabled Capability.

A Scenario-Based Architecture Evaluation Framework for Network Enabled Capability

The vision of service-oriented computing is one of loosely coupled services that create agile applications to encapsulate business objectives and processes. The potential of services to form complex systems of systems, with emergent behaviour, necessitates the need to understand how we can we develop sufficient confidence in their qualities. In this paper we argue that successful development and evolution of service oriented computing is dependent on making informed decisions at the architectural level. This poses a number of challenges concerning how to evaluate such system architectures and the measurements and metrics that are important in their assessment. This paper describes research-in-progress into the development of a scenario-based architectural evaluation framework that allows architectural-level reasoning across systems of systems in the context of Network Enabled Capability: a UK Ministry endeavour designed to achieve enhanced[military] effect through the physical networking and coherent integration of existing and future resources.