Introducing trust and reputation into multi-agent systems can significantly improve the quality and efficiency of the systems. The computational trust and reputation also creates an environment of survival of the fittest to help agents recognize and eliminate malevolent agents in the virtual society. The thesis redefines the computational trust and analyzes its features from different aspects. A systematic model called Neural Trust Model for Multi-agent Systems is proposed to support trust learning, trust estimating, reputation generation, and reputation propagation. In this model, the thesis innovates the traditional Self Organizing Map (SOM) and creates a SOM based Trust Learning (STL) algorithm and SOM based Trust Estimation (STE) algorithm. The STL algorithm solves the problem of learning trust from agents' past interactions and the STE solve the problem of estimating the trustworthiness with the help of the previous patterns. The thesis also proposes a multi-agent reputation mechanism for generating and propagating the reputations. The mechanism exploits the patterns learned from STL algorithm and generates the reputation of the specific agent. Three propagation methods are also designed as part of the mechanism to guide path selection of the reputation. For evaluation, the thesis designs and implements a test bed to evaluate the model in a simulated electronic commerce scenario. The proposed model is compared with a traditional arithmetic based trust model and it is also compared to itself in situations where there is no reputation mechanism. The results state that the model can significantly improve the quality and efficacy of the test bed based scenario. Some design considerations and rationale behind the algorithms are also discussed based on the results.

Aspect-Oriented Software Development provides a means to modularize concerns of a system which are scattered over multiple system modules. These concerns are known as crosscutting concerns and they cause code to be scattered and tangled in multiple system units. The technique was first proposed at the programming level but evolved up through to the other phases of the software development lifecycle with the passage of time. At the moment, aspect-orientation is addressed in all phases of software development, such as requirements engineering, architecture, design and implementation. This thesis focuses on aspect oriented software design and provides a design language, Aspect-Oriented Design Language (AODL), to specify, represent and design aspectual constructs. The language has been designed to implement co-designing of aspectual and non aspectual constructs. The obliviousness between the constructs has been minimized to improve comprehensibility of the models. The language is applied in three phases and for each phase a separate set of design notations has been introduced. The design notations and diagrams are extensions of Unified Modelling Language (UML) and follow UML Meta Object Facility (UML MOF) rules. There is a separate notation for each aspectual construct and a set of design diagrams to represent their structural and behavioural characteristics. In the first phase, join points are identified and represented in the base program. A distinct design notation has been designated for join points, through which they are located using two diagrams, Join Point Identification Diagram and Join Point Behavioural Diagram. The former diagram identifies join points in a structural depiction of message passing among objects and the later locates them during the behavioural flow of activities of the system. In the second phase, aspects are designed using an Aspect Design Model that models the structural representation of an aspect. The model contains the aspect‟s elements and associations among them. A special diagram, known as the pointcut advice diagram, is nested in the model to represent relationship between pointcuts and their related advices. The rest of the features, such as attributes, operations and inter-type declarations are statically represented in the model. In the third and the final phase, composition of aspects is designed. There are three diagrams included in this phase. To design dynamic composition of aspects with base classes, an Aspect-Class Dynamic Model has been introduced. It depicts the weaving of advices into the base program during the execution of the system. The structural representation of this weaving is modelled using Aspect-Class Structural Model, which represents the relationships between aspects and base classes. The third model is the Pointcut Composition Model, which is a fine-grained version of the Aspect-Class Dynamic Model and has been proposed to depict a detailed model of compositions at pointcut-level. Besides these models, a tabular specification of pointcuts has also been introduced that helps in documenting pointcuts along with their parent aspects and interacting classes. AODL has been evaluated in two stages. In the first stage, two detailed case studies have been modelled using AODL. The first case study is an unimplemented system that is forward designed using AODL notations and diagrams, and the second is an implemented system which is reverse engineered and designed in AODL. A qualitative evaluation has been conducted in the second stage of evaluation to assess the efficacy and maturity of the language. The evaluation also compares the language with peer modelling approaches.

Since the first application of fuzzy logic in the field of control engineering, fuzzy logic control has been successfully employed in controlling a wide variety of applications, such as commercial appliances, industrial automation, robots, traffic control, cement kilns and automotive engineering. The human knowledge on controlling complex and non-linear processes can be incorporated into a controller in the form of linguistic expressions. Despite these achievements, however, there is still a lack of an empirical or analytical design study which adequately addresses a systematic auto-tuning method. Indeed, tuning is one of the most crucial parts in the overall design of fuzzy logic controllers and it has become an active research field. Various techniques have been utilised to develop algorithms to fine-tune the controller parameters from a trial and error method to very advanced optimisation techniques. The structure of fuzzy logic controllers is not straightforward as is the case in PID controllers. In addition, there is also a set of parameters that can be adjusted, and it is not always easy to find the relationship between the parameters and the controller performance measures. Moreover, in general, controllers have a wide range of setpoints; changing from one value to another requiring the controller parameters to be re-tuned in order to maintain a satisfactory performance over the entire range of setpoints. This thesis deals with the design and implementation of a new intelligent algorithm for fuzzy logic controllers in a wireless network structure. The algorithm enables the controllers to learn about their plants and systematically tune their gains. The algorithm also provides the capability of retaining the knowledge acquired during the tuning process. Furthermore, this knowledge is shared on the network through a wireless communication link with other controllers. Based on the relationships between controller gains and the closed-loop characteristics, an auto-tuning algorithm is developed. Simulation experiments using standard second order systems demonstrate the effectiveness of the algorithm with respect to auto-tuning, tracking setpoints and rejecting external disturbances. Furthermore, a zero overshoot response is produced with improvements in the transient and the steady state responses. The wireless network structure is implemented using LabVIEW by composing a network of several fuzzy controllers. The results demonstrate that the controllers are able to retain and share the knowledge.

The demand for cost effective, reliable and safe machinery operation requires accurate fault detection and classification. These issues are of paramount importance as potential failures of rotating and reciprocating machinery can be managed properly and avoided in some cases. Various methods have been applied to tackle these issues, but the accuracy of those methods is variable and leaves scope for improvement. This research proposes appropriate methods for fault detection and diagnosis. The main consideration of this study is use Artificial Intelligence (AI) and related mathematics approaches to build a condition monitoring (CM) system that has incremental learning capabilities to select effective diagnostic features for the fault diagnosis of a reciprocating compressor (RC). The investigation involved a series of experiments conducted on a two-stage RC at baseline condition and then with faults introduced into the intercooler, drive belt and 2nd stage discharge and suction valve respectively. In addition to this, three combined faults: discharge valve leakage combined with intercooler leakage, suction valve leakage combined with intercooler leakage and discharge valve leakage combined with suction valve leakage were created and simulated to test the model. The vibration data was collected from the experimental RC and processed through pre-processing stage, features extraction, features selection before the developed diagnosis and classification model were built. A large number of potential features are calculated from the time domain, the frequency domain and the envelope spectrum. Applying Neural Networks (NNs), Support Vector Machines (SVMs), Relevance Vector Machines (RVMs) which integrate with Genetic Algorithms (GAs), and principle components analysis (PCA) which cooperates with principle components optimisation, to these features, has found that the features from envelope analysis have the most potential for differentiating various common faults in RCs. The practical results for fault detection, diagnosis and classification show that the proposed methods perform very well and accurately and can be used as effective tools for diagnosing reciprocating machinery failures.

This dissertation makes two contributions to the field of software verification. The first explains how verification techniques originally developed for concurrency can be usefully applied to sequential programs. The second describes how sequential programs can be verified using diagrams that have a parallel nature. The first contribution involves a new treatment of stability in verification methods based on rely-guarantee. When an assertion made in one thread of a concurrent system cannot be invalidated by the actions of other threads, that assertion is said to be 'stable'. Stability is normally enforced through side-conditions on rely-guarantee proof rules. This dissertation proposes instead to encode stability information into the syntactic form of the assertion. This approach, which we call explicit stabilisation, brings several benefits. First, we empower rely-guarantee with the ability to reason about library code for the first time. Second, when the rely-guarantee method is redepleyed in a sequential setting, explicit stabilisation allows more details of a module's implementation to be hidden when verifying clients. Third, explicit stabilisation brings a more nuanced understanding of the important issue of stability in concurrent and sequential verification; such an understanding grows ever more important as verification techniques grow ever more complex. The second contribution is a new method of presenting program proofs conducted in separation logic. Building on work by Jules Bean, the ribbon proof is a diagrammatic alternative to the standard 'proof outline'. By emphasising the structure of a proof, ribbon proofs are intelligible and hence useful pedagogically. Because they contain less redundancy than proof outlines, and allow each proof step to be checked locally, they are highly scalable; this we illustrate with a ribbon proof of the Version 7 Unix memory manager. Where proof outlines are cumbersome to modify, ribbon proofs can be visually manoeuvred to yield proofs of variant programs. We describe the ribbon proof system, prove its soundness and completeness, and outline a prototype tool for mechanically checking the diagrams it produ1res.

M.Ing.

Looking at software engineering from a historical perspective, we can see how software development methodologies have evolved over the past 50 years. Using the right software development methodology with the right settings has always been a challenge. Therefore, there has always been a need for empirical evidence about what worked well and what did not, and what factors affect the different variables of the development process. Probably the most noticeable change to software development methodology in the last 15 years has been the introduction of the word “agile”. As any area matures, there is a need to understand its components and relations, as well as the need of empirical evidence about how well agile methods work in real life settings. In this thesis, we empirically investigate the impact of agile methods on different aspects of quality including product quality, process quality and stakeholders’ satisfaction as well as the different factors that affect these aspects. Quantitative and qualitative research methods were used for this research, including semi-structured interviews and surveys. Quality was studied in two projects that used agile software development. The empirical study showed that both projects were successful with multiple releases, and with improved product quality and stakeholders’ satisfaction. The data analysis produced a list of 13 refined grounded hypotheses out of which 5 were supported throughout the research. One project was studied in-depth by collecting quantitative data about the process used via a newly designed iteration monitor. The iteration monitor was used by the team over three iterations and it helped identify issues and trends within the team in order to improve the process in the following iterations. Data about other organisations collected via surveys was used to generalise the obtained results. A variety of statistical analysis techniques were applied and these suggested that when agile methods have a good impact on quality they also has a good impact on productivity and satisfaction, also when agile methods had good impact on the previous aspects they reduced cost. More importantly, the analysis clustered 58 agile practices into 15 factors including incremental and iterative development, agile quality assurance, and communication. These factors can be used as a guide for agile process improvement. The previous results raised questions about agile project governance, and to answer these questions the agile projects governance survey was conducted. This survey collected 129 responses, and its statistically significant results suggested that: retrospectives are more effective when applied properly as they had more impact when the whole team participated and comments were recorded, that organisation size has a negative relationship with success, and that good practices are related together as when a team does one aspect well, they do all aspects well. Finally, the research results supported the hypotheses: agile software development can produce good quality software, achieve stakeholders’ satisfaction, motivate teams, assures quick and effective response to stakeholder’s requests, and it goes in stages, matures, and improves over time.

The ability to build tools that support gathering and querying information from distributed sources on the Web rests on the availability of structured data. Linked Data, as a way for publishing and linking distributed structured data sources on the Web, provides an opportunity to create this kind of tools. Currently, however, the ability to complete such tasks over Linked Data sources is limited to users with advanced technical skills, resulting in an online information space largely inaccessible to non-technical end users. This thesis explores the challenges of designing user interfaces for end users, those without technical skills, to use Linked Data to solve information tasks that require combining information from multiple sources. The thesis explores the design space around interfaces that support access to Linked Data on demand, suggests potential use cases and stakeholders, and proposes several direct manipulation tools for end users with diverse needs and skills. User studies indicate that the tools built offer solutions to various challenges in accessing Linked Data that are identified in this thesis.

No description available.

In the software engineering world, many modelling notations and languages have been developed to aid application development. The technologies, Java and Web services, play an increasingly important role in web applications. However, because of issues of complexity, it is difficult to build multi-threaded Java applications and Web Service applications, and even more difficult to model. Furthermore, it is difficult to reconcile the directly-coded application with the model-based application. Based on the formal modelling system, RDT, the new work here covers: (i) a translator, RDTtoJava, used to automatically convert an RDT model into an executable multi-threaded Java application; (ii) the framework for developing an RDT model into a Java synchronous distributed application that is supported by the JAX-RPC Web Services; and, (iii) the framework for developing an RDT model into a Java asynchronous distributed application that is supported by the JMS Web services. Experience was gained by building distributed computing models and client/server models and generation of the application based on such models. This work is helpful for the software developers and software researchers in formal software development.