Stephen Milliner

Event-Based coordination of process-oriented composite applications

A process-oriented composite application aggregates functionality from a number of other applications and coordinates these applications according to a process model. Traditional approaches to develop process-oriented composite application rely on statically defined process models that are deployed into a process management engine. This approach has the advantage that application designers and users can comprehend the dependencies between the applications involved in the composition by referring to the process model. A major disadvantage however is that once deployed the behaviour of every execution of the composite application is expected to abide by its process model until this model is changed and re-deployed. This makes it difficult to enrich the application with even minor features, to plug-in new applications into the composition, or to hot-fix the composite application to meet special circumstances or demands (e.g. to personalise the application). This paper describes a technique for translating a process-oriented application into an event-based application which is more amenable to such runtime adaptation. The process-based and event-based views of the application can then co-exist and be synchronised offline if the changes become permanent and it is found desirable to reflect them in the process model.

An evolutionary learning approach for adaptive negotiation agents

Developing effective and efficient negotiation mechanisms for real‐world applications such as e‐business is challenging because negotiations in such a context are characterized by combinatorially complex negotiation spaces, tough deadlines, very limited information about the opponents, and volatile negotiator preferences. Accordingly, practical negotiation systems should be empowered by effective learning mechanisms to acquire dynamic domain knowledge from the possibly changing negotiation contexts. This article illustrates our adaptive negotiation agents, which are underpinned by robust evolutionary learning mechanisms to deal with complex and dynamic negotiation contexts. Our experimental results show that GA‐based adaptive negotiation agents outperform a theoretically optimal negotiation mechanism that guarantees Pareto optimal. Our research work opens the door to the development of practical negotiation systems for real‐world applications.

A process-based methodology for designing event-based mobile composite applications

Mobile application developers should be able to specify how applications can adapt to changing conditions, and to later reconfigure the application to suit new circumstances. Event-based communication have been advocated to facilitate such dynamic changes. Event-based models, however, are fragmented, which makes it difficult to understand the dependencies between components. A process-oriented methodology overcomes this issue, by specifying dependencies according to a process model. This paper describes a methodology that combines the comprehensibility and manageability of control from process-oriented methodologies, with the flexibility of event-based communication. This enables fine-grained adaptation of process-oriented applications.

The 3DMA Middleware for Mobile Applications

Research in mobile devices have received extensive interest in recent years. Mobility raises new issues such as more dynamic context, limited computing resources, and frequent disconnections. To handle these issues, we propose a middleware, called 3DMA, which addresses three requirements: 1) decomposition, 2) distribution and 3) decoupling. 3DMA uses a space based approach combined with a set of “workers” which are able to act on the users behalf either to reduce load on the mobile device, or to support disconnected behavior. In order to demonstrate aspects of the middleware architecture we consider the development of a mobile application.

Middleware support for mobile applications

Mobile devices have received much research interest in recent years. Mobility raises new issues such as more dynamic context, limited computing resources, and frequent disconnections. A middleware infrastructure for mobile computing must handle all these issues properly. In this project we propose a middleware, called 3DMA, to support mobile computing. We introduce three requirements, distribution, decoupling and decomposition as central issues for mobile middleware. 3DMA uses a space based middleware, which facilitates the implementation of decoupled behavior and support for disconnected operation and context awareness. This is done by defining a set of “workers” which are able to act on the users behalf either: to reduce load on the mobile device, and/or to support disconnected behavior. In order to demonstrate aspects of the middleware architecture we then consider the development of a commonly used mobile application.

Experience using a coordination-based architecture for adaptive web content provision

There are many ways of achieving scalable dynamic web content. In previous work we have focused on dynamic content degradation using a standard architecture and a design-time “Just In Case” methodology. In this paper, we address certain shortcomings witnessed in our previous work by using an alternate coordination-based architecture, which has interesting applicability to run-time web server adaptation. We first establish the viability of using this architecture for high-volume dynamic web content generation. In doing so, we establish its ability to maintain high throughput in overload conditions. We go on to show how we used the architecture to achieve a “Just In Time” adaptation to achieve dynamic web content degradation in a running web application server.

Scaling dynamic Web content provision using elapsed-time-based content degradation

Dynamic Web content is increasing in popularity and, by its nature, is harder to scale than static content. As a result, dynamic Web content delivery degrades more rapidly than static content under similar client request rates. Many techniques have been explored for effectively handling heavy Web request traffic. In this paper, we concentrate on dynamic content degradation, believing that it offers a good balance between minimising total cost of ownership and maximising scalability.

Resource location in large scale heterogeneous and autonomous databases

In many large organizations there has been a proliferation of database systems to handle ever increasing volumes of information. In order to explore a potentially huge on-line information space, we must develop an architecture which allows for the dynamic data driven construction of inter-database node relationships in an incremental manner. In this paper we introduce the FINDIT architecture which uses informationmeta-types to provide a basis for such an organization and, consequently, provides a platform for interoperability. A distinction is made between theinformation andinter-node relationship spaces to achieve scalability. Tassili language primitives are used for the incremental building of dynamic inter-node relationships based upon usage considerations.

Varying resource consumption to achieve scalable Web services

Web service deployment is hampered by the possibility of sudden variations in request volumes. Mechanisms exist to enhance scalability in times of heavy load when the delivered content is static. However, web services typically involve dynamic content, delivered through application servers which may have little to no support for adapting to varying loads in order to ensure timely delivery. In this paper we discuss why scaling dynamic content delivery under load is difficult, we present a technique for controlled service degradation to achieve this scalability, and we present experimental results evaluating its benefits.