Nigel Baker

Survey of Context Provisioning Middleware

In the scope of ubiquitous computing, one of the key issues is the awareness of context, which includes diverse aspects of the users situation including his activities, physical surroundings, location, emotions and social relations, device and network characteristics and their interaction with each other. This contextual knowledge is typically acquired from physical, virtual or logical sensors. To overcome problems of heterogeneity and hide complexity, a significant number of middleware approaches have been proposed for systematic and coherent access to manifold context parameters. These frameworks deal particularly with context representation, context management and reasoning, i.e. deriving abstract knowledge from raw sensor data. This article surveys not only related work in these three categories but also the required evaluation principles.

ContextML: A light-weight context representation and context management schema

Context representation is a fundamental process in developing context aware systems for the pervasive world. We present a light weight XML based context representation schema called ContextML in which context information is categorized into scopes and related to different types of entities (e.g. user, device). The schema is also applied for encoding management messages in order to allow for a flexible framework supporting gradual plug & play extendibility and mobility. ContextML is tailored to be used for REST-based communication between the framework components. Explanation of the schema is provided with the help of real world examples. Moreover, the European C-CAST testbed is introduced, embracing a variety of context providers and application domains.

A context provisioning framework to support pervasive and ubiquitous applications

Acquisition and dissemination of user and environment context information is critical in development and deployment of context-aware systems. It is fundamental to the success of such systems that they have access to a scaleable, robust and flexible context provisioning framework capable of working across all types of devices and networks. In this paper, we present the design, implementation and experiences of developing a context management system that incorporates these ideas. It is based on a consumer-provider broker model, where providers employ a common context representation format, decoupling various entities involved in the production and consumption of context information. We demonstrate how the idea of independent context providers can aid in end-to-end working of a context management framework. One of the major advantages compared to other approaches is the extendibility of the system. By progressively adding Context Providers to legacy mobile communication systems, new context domains can be added. The system is able to evolve constantly and support a variety of emerging context-aware services and applications.

A Federated Broker Architecture for Large Scale Context Dissemination

Dissemination of context data from context producing entities to context consuming entities is a fundamental functional task of context aware systems. Broker based approaches have been successfully demonstrated in a number of prototype context-aware systems. With the increase in sensing capabilities of mobile devices, such devices are not merely consumers of context information any more but also have the ability to be \emph{providers} of context gathered through integrated sensors. In such a provider-consumer model, where context dissemination is aided by a central broker, device-broker interaction can become a communication and computation bottleneck in presence of multiple context providers and consumers in mobile devices. In this paper we present a theoretical model for a large scale context-aware system based on a federation of multiple context brokers and discuss the concept of a mobile broker to facilitate the participation of mobile devices in context provision and consumption efficiently. The utilisation of an asynchronous event-based publish-subscribe paradigm is focused as a key element.

Effect of caching in a broker based context provisioning system

Caching is a well-established mechanism used in distributed systems for improving overall performance. In this paper, we analyse the effect of using a context cache in a broker-based context provisioning system. An experiment is carried out using a simulation based on our framework architecture of context consumers, context broker and context providers exchanging different types of context data over time. The results show notable improvement in the context query response time.

An object model for product and workflow data management

In industry design engineers have traditionally employed Product Data Management Systems to coordinate and control access to documented versions of product designs. However, these systems provide control only at the collaborative design level and are seldom used beyond design. Workflow management systems, on the other hand, are employed in industry to coordinate and support the more complex and repeatable work processes of the production environment. The integration of Product Data Management with Workflow Management can provide support for product development from initial CAD/CAM collaborative design through to the support and optimisation of production workflow activities. This paper investigates this integration and proposes a data model for the support of product data throughout the full development and production lifecycle and demonstrates its usefulness in the construction of large scale high energy physics detectors at the European Particle Physics laboratory at CERN.

IMS-MBMS Convergence for Next Generation Mobile Networks

Mobile and wireless communication standards and technologies have witnessed rapid enhancements in the last few years. Dynamic, interactive, rich content and location based services such as IPTV, multimedia conferencing, buddy lists and presence have emerged. However, multimedia services often prove to be heavy on radio resources and multicast or broadcast is a resource efficient transmission mode. Currently, IMS only supports unicast transmission, so 3GPP MBMS is selected as the broadcast/multicast delivery technology. In this paper, we propose a converged IMS and MBMS architecture, designed to support the next generation of multimedia multicast services. A comprehensive network entity design is also elaborated. This work is carried out as part of EU-IST project C-MOBILE (IST-2005-27423).

Object databases in a distributed scientific workflow application

The construction of large scientific experiments (such as the Compact Muon Solenoid experiment being undertaken for CERN) necessitates the use of complex production management operations, often distributed over many geographically separated research institutes. These workflow operations are often only loosely-defined at the outset of the construction and can evolve rapidly as the results of experiments are analysed. Existing commercial workflow management systems are largely based on relational database management systems (RDBMSs) and are unable to cope with the requirements of such scientific workflow environments and, in particular, with the dynamic schema evolution which results from the rapidly evolving scientific workflow definitions. This paper reports on the requirements for object repositories in the implementation of a prototype scientific workflow management system entitled CRISTAL (Cooperating Repositories and an Information System for Tracking Assembly Lifecycles) and considers issues surrounding data duplication between object repositories and scientific workflow management in CRISTAL.

Version management in a distributed workflow application

Most applications of workflow management in business are based on well-defined repetitively executed processes. Recently, workflow management principles have been applied to the scientific and engineering communities, where activities may dynamically change as the workflows are executed and may often evolve through multiple versions. These domains present new problems including tracking the progress of parts on which those activities are executed, particularly if the production process itself is distributed across multiple sites. A major requirement of the system is that the full production history of every part must be permanently stored. This paper reports on the activities of a large-scale distributed scientific workflow management project, entitled CRISTAL (Cooperating Repositories and Information System for the Tracking of Assembly Lifecycles), in which a product data management (PDM) system is used to store and maintain versions of workflow meta-objects and in which a light-weight workflow enactment component is implemented for execution. These versions must support the permanent recording of a constantly adapting production process. The workflow enactment component is based on Petri nets, which are designed to embody all aspects of the scientific workflow management.

Towards global smart spaces: Merge Wireless Sensor Networks into context-aware systems

The integration of Wireless Sensor Networks at a global scale is a crucial step on the road to a tighter coupling between the virtual and real world. In a context-aware system with thousands or even millions of data items describing the current situation, it is obvious that this data needs to be filtered and aggregated in order to distribute the detection and processing efficiently. The need to aggregate data exists also from the perspective of the Wireless Sensor Network since energy is limited and there is a strong requirement to reduce communication traffic. Therefore, this paper illustrates the general concept of a context-aware system and explains in detail how to integrate Wireless Sensor Networks in such a system for global usage of information detected by numerous nodes. The concept is proven by implementation, measurements, and a theory of operation.