Reactive system model for building fault-tolerant distributed applications

The development of fault-tolerant computing systems is a very difficult task. Two reasons contributed to this difficulty can be described as follows. The First is that, in normal practice, fault-tolerant computing policies and mechanisms are deeply embedded into most application programs, so that these application programs cannot cope with changes in environments, policies and mechanisms. These factors may change frequently in a distributed environment, especially in a heterogeneous environment. Therefore, in order to develop better fault-tolerant systems that can cope with constant changes in environments and user requirements, it is essential to separate the fault tolerant computing policies and mechanisms in application programs. The second is, on the other hand, a number of techniques have been proposed for the construction of reliable and fault-tolerant computing systems. Many computer systems are being developed to tolerant various hardware and software failures. However, most of these systems are to be used in specific application areas, since it is extremely difficult to develop systems that can be used in general-purpose fault-tolerant computing. The motivation of this thesis is based on these two aspects. The focus of the thesis is on developing a model based on the reactive system concepts for building better fault-tolerant computing applications. The reactive system concepts are an attractive paradigm for system design, development and maintenance because it separates policies from mechanisms. The stress of the model is to provide flexible system architecture for the general-purpose fault-tolerant application development, and the model can be applied in many specific applications. With this reactive system model, we can separate fault-tolerant computing polices and mechanisms in the applications, so that the development and maintenance of fault-tolerant computing systems can be made easier.

Experiences gained from building a services-based distributed operating system

The goal of this paper is to present the experiences gained over 15 years of research into the design and development of a services-based distributed operating system. The lessons learnt over this period, we hope, will be of value to researchers involved in the design and development of operating systems that wish to harness the collective resources of ever-expanding distributed systems.

User-centered design and evaluation of an interactive visual-haptic-auditory interface : a user study on assembly

Utilizing user-centred system design and evaluation method has become an increasingly important tool to foster better usability in the field of virtual environments (VEs). In recent years, although it is still the norm that designers and developers are concerning the technological advancement and striving for designing impressive multimodal multisensory interfaces, more and more awareness are aroused among the development team that in order to produce usable and useful interfaces, it is essential to have users in mind during design and validate a new design from users' perspective. In this paper, we describe a user study carried out to validate a newly developed haptically enabled virtual training system. By taking consideration of the complexity of individual differences on human performance, adoption and acceptance of haptic and audio-visual I/O devices, we address how well users learn, perform, adapt to and perceive object assembly training. We also explore user experience and interaction with the system, and discuss how multisensory feedback affects user performance, perception and acceptance. At last, we discuss how to better design VEs that enhance users perception, their interaction and motor activity.

Functional system maps as boundary objects in complex system development

A trend towards the provision of product-service packaging and the proliferation of service businesses introduces both tangible and intangible elements into system design. In this paper, we consider the utility of hierarchical system models as a way of flexibly combining such elements by focusing on requisite functionality. Four cases illustrate how the same approach may be used to clarify the requirements of business or socio-technical systems during system development, operation or reengineering stages. It is suggested that a suitable loosely coupled model has significant utility as a 'boundary object' - a term first coined in the study of museum artefacts. Discussion of such objects requires the use of imagination, which may support innovative system design and development. It is suggested that a well-crafted model has multiple uses - as a foundation for system development, in combining traditional and agile project management strategies and in providing a framework to facilitate the capture and organisation of project knowledge.

A solution for fault tolerance in replicated database systems

A distributed database system is subject to site failure and link failure. This paper presents a reactive system approach to achieving fault tolerance in such a system. The reactive system concepts are an attractive paradigm for system design, development and maintenance because it separates policies from mechanisms. In the paper we give a solution using different reactive modules to implement the fault tolerant policies and the failure detection mechanisms. The solution shows that they can be separated without impact on each other; thus the system can adapt to constant changes in environments and user requirements.

A security method for healthcare organisations

The use of participational approaches to system design has been debated for a number of years. Within this paper we describe a method that was used to effectively design information systems and implement computer security countermeasures within an health care environment and shown how it was used in a number of environments.

A solution for fault-tolerance in replicated database systems

A distributed database system is subject to site failure and link failure. This paper presents a reactive system approach to achieving the fault-tolerance in such a system. The reactive system concepts are an attractive paradigm for system design, development and maintenance because it separates policies from mechanisms. In the paper we give a solution using different reactive modules to implement the fault-tolerant policies and the failure detection mechanisms. The solution shows that they can be separated without impact on each other thus the system can adapt to constant changes in user requirements.

Crossing the border : comparing partial and fully online learning

In many countries across the world, online learning is playing an ever-increasing role in higher education. However, there seem to be starkly contrasting analyses of the educational value of online learning. In this paper, I reflect on my own online learning experiences in the UK and Australia and conclude that there are significant differences between partial and fully online course units. I also develop general criticisms of online learning system design and suggest a number of fundamental design and performance objectives for the design of online learning systems.

Reliable event transfer in wireless sensor networks deployed for emergency response

Sensor Networks have applications in diverse fields. They can be deployed for habitat modeling, temperature monitoring and industrial sensing. They also find application in battlefield awareness to sense chemicals and other gases used in chemical and biological warfare. An application that has become increasingly attractive in the post 9/11 era is the use of wireless sensor networks for emergency (first) response in mass casualty incidents. Reliability of data and event transfer is of critical importance to emergency response applications. In this work we propose a reliable event transfer mechanism making use of an overlay network of relay nodes. The overlay network removes the burden of data relaying from the sensor nodes and results in increasing the lifetime of the network. Simulation results prove the benefits of such an architecture. Reliability is increased 10-30% with reduction in event traffic of 60-80%.

Lease based addressing for event-driven wireless sensor networks

Sensor Networks have applications in diverse fields. They can be deployed for habitat modeling, temperature monitoring and industrial sensing. They also find applications in battlefield awareness and emergency (first) response situations. While unique addressing is not a requirement of many data collecting applications of wireless sensor networks it is vital for the success of applications such as emergency response. Data that cannot be associated with a specific node becomes useless in such situations. In this work we propose an addressing mechanism for event-driven wireless sensor networks. The proposed scheme eliminates the need for network wide Duplicate Address Detection (DAD) and enables reuse of addresses.

A participational security method for healthcare organisations

The use of participational approaches in system design have been debated for a number of years. Within this paper we describe a method that was used to effectively design information systems and implement information security countermeasures within a health care environment. The paper shows how it was used in a number of different environments.

Enabling industrial scale simulation / emulation models

OLE Process Control (OPC) is an industry standard that facilitates the communication between PCs and Programmable Logic Controllers (PLC). This communication allows for the testing of control systems with an emulation model. When models require faster and higher volume communications, limitations within OPC prevent this. In this paper an interface is developed to allow high speed and high volume communications between a PC and PLC enabling the emulation of larger and more complex control systems and their models. By switching control of elements within the model between the model engine and the control system it is possible to use the model to validate the system design, test the real world control systems and visualise real world operation.

Industrial application of thermal image processing and thermal control

Industrial application of infrared thermography is virtually boundless as it can be used in any situations where there are temperature differences. This technology has particularly been widely used in automotive industry for process evaluation and system design. In this work, thermal image processing technique will be introduced to quantitatively calculate the heat stored in a warm/hot object and consequently, a thermal control system will be proposed to accurately and actively manage the thermal distribution within the object in accordance with the heat calculated from the thermal images.

Designing on-line learning systems using participation

The review of literature pertaining to systems analysis and design and the design of systems for on-line teaching and learning has identified some "gaps" and shown the need for participation in educational system design. This paper presents research which was conducted to develop an approach for the design of educational systems involving the participation of student and academics in the design of educational on-line learning systems.