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The concern of this thesis is the development of software for systems utilising embedded processors. In many cases, the safety of users of “embedded systems” (and other people in the immediate vicinity) depends on the correct operation of this software. This project explores the ways in which the cost of designing, implementing and verifying the behaviour of systems that include embedded software can be reduced. More specifically, the goal is to determine the extent to which the use of a time-triggered (TT) architecture - as opposed to an equivalent “event triggered” (ET) architecture - could offer benefits to the developers of reliable embedded systems. To evaluate this, a method of software architecture evaluation was developed and is described. The work detailed in this thesis involved an extensive empirical study of the costs involved in testing TT systems, with and without task pre-emption. Factors considered in this comparison included: [i] implementation costs, including code size, overhead, memory and CPU utilisation of a scheduler; [ii] testing costs, including the ease of obtaining timing data for isolated and in-situ tasks; and [iii] design costs, including execution time, lines of code and number of inputs required to perform a test of schedulability on the task set. The results from empirical studies suggested the use of TT architectures (compared with equivalent designs based on ET architectures) would require greater efforts at the design phase, but lower efforts during the testing phases. The results also suggested systems based on TT designs are likely to have lower implementation costs than equivalent systems based on ET designs. Taken together, the results point to a lower overall cost for TT systems. Execution of the method is described through the presentation of experimental case studies. Throughout these activities, the method has been shown to be a capable tool for software architecture evaluation.

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Software architecture is a generally accepted discipline. Nevertheless, none of the existing definitions has been accepted as a suitable standard. Consequently, software architecture and Architecture Description Languages are commonly characterised by the entire collection of expert views on that subject. However, each of the existing definitions falls short for various reasons in providing a definitive answer to the purpose and addressee of software architecture. This dissertation assumes that its addressee is the human and its purpose is aimed at comprehension, this being a prerequisite for any human activity in the software lifecycle. One further open issue of existing definitions includes the question of whether, or to what extent, the specification of the functional requirements should be regarded as part of software architecture.

Information technology (IT) plays an important role in the banking sector, enabling customers to have access to financial services at any time in any location. However, due to little consideration to the need for flexibility in business, many systems require intensive maintenance and improvement during their lifetime. It therefore becomes vital to provide an effective solution for systems evaluations to examine the alignment of current facilities with respect to requirements for reengineering IT systems. A great amount of effort has been made to address this issue. There are three major challenges in the evaluation of systems alignment. First, the context of business requirements is very broad and hard to cover; this may cause difficulties in the proper articulation of contextual information during the systems evaluation. Second, a question has been raised on how to represent the elicited requirements into an integrated manner and precisely identify the corresponding functionality in IT systems. Third, the identification mechanism may return a set of IT candidates, amongst which are ranked according to the suitability and criticality for alignment has become a greater challenge. The research investigates the business context from a service perspective, by exploring the possibility of employing a business process topology to facilitate IT systems evaluation. The research defines two dimensions of business contextual information (i.e. the customers' service selection and business process topology), and specifies business requirements through dynamic modelling of customer profiles, service characteristics and business processes. Following an understanding of the diversity of business requirements, this research focuses on matching business requirements onto a set of suitable IT services. There are two steps in the matchmaking: (i) IT systems discovery, and (ii) IT systems valuation and selection. This research provides an IT service matchmaking model that enables the matchmaking of suitable IT functionalities against business requirements. It further evaluates selected IT systems to determine whether the application systems were fit for purpose for both their functional requirements and non-functional requirements. In cases where there are duplications of the systems functions, the IT systems matchmaking model returns a set of candidates. The probabilistic framework proposed in this research is used to rank these candidates in accordance with the suitability and criticality for IT systems alignment. The end result of this research is a service-centric framework for Evaluating IT Systems Alignment (EITSA). EITSA consists of three methods: a topology of customer service-centric business process, a norm-based method for business process modelling and a method for evaluating IT systems alignment. EITSA provides an effective solution for business and IT alignment, which is a prerequisite for IT systems reconfiguration. A number of techniques, such as customer classification, process decomposition and specification, and a service matchmaking engine have been developed to facilitate IT systems evaluation, which ultimately assesses the degree of systems alignment. The outcome of the research, EITSA, is validated through case studies in Chinese banking organisations.