Distributed simulation provides an alternative solution when today's highly complicated systems including manufacturing are to be simulated. Complexities involved in implementation, the need for more expertise, high development cost and long implementation time etc. along with a lack of guidelines for developing distributed simulation, and the complexity of tools and techniques used to implement schemes, resulted in the lack of acceptance for distributed simulation among the general simulation community. In order to address some of these issues, a new approach is proposed for modelling and simulating large scale enterprises using distributed simulation. The proposed approach which includes a comprehensive methodology for distributed enterprise simulation, developed by combining activities required for traditional sequential simulation with additional activities required for distributed simulation. The thesis elaborates the additional activities required for distributed simulation in different chapters with simplified approaches for carrying out these activities. These include an approach to decide the appropriate simulation strategy (SimSS process), a simplified approach to modelling and model partitioning, a synchronization mechanism that approximately synchronizes the distributed enterprise simulation and an approach for developing distributed simulation using tools and technologies which are popular, well accepted and also cost effective. The differences between the traditional distributed simulation approaches and the proposed methodology include: partitioning of the conceptual model into logical processes before transforming them into computer simulation models, use of commercial simulation software to implement the distributed simulation, and use of cost effective and popular middleware and programming languages. Illustration of the proposed approaches focuses on distributed manufacturing applications.

One of deficiencies in the Z tools is that there is limited support for model checking Z specifications. To build a model checker directly for a Z specification would take considerable effort and time due to the abstraction of the language. Translating inputs of a Z specification into a language that an existing model checker tool accepts is an alternative method. Researchers at the University of Sheffield implemented a translation tool which took a Z specification and translated it into the input for the Symbolic Analysis Laboratory (SAL) tool, a framework for combining different tools for abstraction, program analysis, theorem proving and model checking, which they called Z2SAL. In this paper, support for model checking Z specifications is discussed, in which the ability of the existing Z2SAL is extended. This support includes a translation for generic constant and schema calculus. Instead of translating these aspects of the Z language into the SAL language as Z2SAL does, a Z specification containing these two notations will be pre-processed,in which a generic constant definition will be redefined to its equivalent axiomatic definition, and schema calculus will be expanded to a new schema definition. This paper discusses the implementation of these types of support, and illustration of some working examples. The discussion also includes other several issues related to a new approach in translating Z functions and constants in SAL language, which originates from the type incompatibility obtained during execution by the SAL tool, an approach to a SAL translation of embedded theorems on Z specifications, and a manual experiment on applying an abstraction on Z specifications. Results have been gathered during our experiments with the implemented support. Several of these results could be translated by Z2SAL and be executed by the SAL tool.

The main advantages of random error-correcting majority-logic codes and majority-logic decoding in general are well known and two-fold. Firstly, they offer a partial solution to a classical coding theory problem, that of decoder complexity. Secondly, a majority-logic decoder inherently corrects many more random error patterns than the minimum distance of the code implies is possible. The solution to the decoder complexity is only a partial one because there are circumstances under which a majority-logic decoder is too complex and expensive to implement.

The academic literature hitherto has mainly addressed the 'effects' of video games and not their creation. The thesis seeks to gain an understanding of the motivations behind the design choices in creating home computer and video games software in light of this 'gap'. The research sought to understand the process of constructing games by examining: (i) the individual designer's aims and how these were mediated by the contexts of. - (ii) the development team and organisation; (iii) the needs of the audience and their presence in the innovation process and (iv) the impact of the hardware manufacturer's quality assessment upon the game's design. These aims were met by outlining the industry structure operating in the video games' market from the period between the early 1980s to mid-1990s. This was performed with reference to the rise of Sega and Nintendo's hardware and software strategy, covering their diffusion from Japan to the US and UK. This highlighted the context surrounding the creation of three computer games from initial concept to actual commodity that served as the subject of case study analysis. The discussion seeks to explore the implications of the choices made in designing the games and widens the debate to the creation of other games. It is argued that the design of games mirrors aspects similar to the creation of other entertainment media but possess certain problems associated with aesthetic conventions, labour, industry and technical issues unique to this medium. Consequently the thesis outlines certain dimensions that impinge'upon the process of product innovation in entertainment software. From a theoretical perspective the application of a social constructivist approach to the emergence of a leisure technology is a novel one and demonstrates the contingent nature of game design.

Building reliable systems is one of the major challenges faced by software developers as society is becoming more dependent on software systems. The failure of any system can lead to a serious loss, for example serious injury or death in case of safety critical systems and significant financial loss in the case of business-critical systems. As a consequence, fault tolerance is considered as a solution to provide reliability, but the fault tolerance capability is associated with many challenges, such as the right development phase where it needs to be introduced, how it can be composed with the software, and the issues that arise from this composition such as complexity and potential undesirable feature interactions. This thesis presents an orthogonal fault tolerance framework for the composition of design diversity fault tolerance mechanism with the base system. It further ensures the separation of concerns between the ‘base’ system and the fault tolerance mechanisms that are composed with the base system. The composition in this framework is based on operational semantics that describe the behaviour of the underlying components when composed with the fault tolerance mechanisms. A custom-built pre-processor is based on these composition rules, and is used to automatically compose the system component and the fault tolerance mechanisms. The very introduction of different fault tolerance mechanisms to the system may cause interactions with other fault tolerance features or with system components. Logic properties written in CTL and LTL are used in NuSMV to analyse undesirable interactions. To illustrate its applicability, the framework has been applied to the Home Automation and Therac-25 software.

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