40 research outputs found

    Assuming Data Integrity and Empirical Evidence to The Contrary

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    Background: Not all respondents to surveys apply their minds or understand the posed questions, and as such provide answers which lack coherence, and this threatens the integrity of the research. Casual inspection and limited research of the 10-item Big Five Inventory (BFI-10), included in the dataset of the World Values Survey (WVS), suggested that random responses may be common. Objective: To specify the percentage of cases in the BRI-10 which include incoherent or contradictory responses and to test the extent to which the removal of these cases will improve the quality of the dataset. Method: The WVS data on the BFI-10, measuring the Big Five Personality (B5P), in South Africa (N=3 531), was used. Incoherent or contradictory responses were removed. Then the cases from the cleaned-up dataset were analysed for their theoretical validity. Results: Only 1 612 (45.7%) cases were identified as not including incoherent or contradictory responses. The cleaned-up data did not mirror the B5P- structure, as was envisaged. The test for common method bias was negative. Conclusion: In most cases the responses were incoherent. Cleaning up the data did not improve the psychometric properties of the BFI-10. This raises concerns about the quality of the WVS data, the BFI-10, and the universality of B5P-theory. Given these results, it would be unwise to use the BFI-10 in South Africa. Researchers are alerted to do a proper assessment of the psychometric properties of instruments before they use it, particularly in a cross-cultural setting

    Leading Towards Voice and Innovation: The Role of Psychological Contract

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    Background: Empirical evidence generally suggests that psychological contract breach (PCB) leads to negative outcomes. However, some literature argues that, occasionally, PCB leads to positive outcomes. Aim: To empirically determine when these positive outcomes occur, focusing on the role of psychological contract (PC) and leadership style (LS), and outcomes such as employ voice (EV) and innovative work behaviour (IWB). Method: A cross-sectional survey design was adopted, using reputable questionnaires on PC, PCB, EV, IWB, and leadership styles. Correlation analyses were used to test direct links within the model, while regression analyses were used to test for the moderation effects. Results: Data with acceptable psychometric properties were collected from 11 organisations (N=620). The results revealed that PCB does not lead to substantial changes in IWB. PCB correlated positively with prohibitive EV, but did not influence promotive EV, which was a significant driver of IWB. Leadership styles were weak predictors of EV and IWB, and LS only partially moderated the PCB-EV relationship. Conclusion: PCB did not lead to positive outcomes. Neither did LS influencing the relationships between PCB and EV or IWB. Further, LS only partially influenced the relationships between variables, and not in a manner which positively influence IWB

    Hierarchical Group and Attribute-Based Access Control: Incorporating Hierarchical Groups and Delegation into Attribute-Based Access Control

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    Attribute-Based Access Control (ABAC) is a promising alternative to traditional models of access control (i.e. Discretionary Access Control (DAC), Mandatory Access Control (MAC) and Role-Based Access control (RBAC)) that has drawn attention in both recent academic literature and industry application. However, formalization of a foundational model of ABAC and large-scale adoption is still in its infancy. The relatively recent popularity of ABAC still leaves a number of problems unexplored. Issues like delegation, administration, auditability, scalability, hierarchical representations, etc. have been largely ignored or left to future work. This thesis seeks to aid in the adoption of ABAC by filling in several of these gaps. The core contribution of this work is the Hierarchical Group and Attribute-Based Access Control (HGABAC) model, a novel formal model of ABAC which introduces the concept of hierarchical user and object attribute groups to ABAC. It is shown that HGABAC is capable of representing the traditional models of access control (MAC, DAC and RBAC) using this group hierarchy and that in many cases it’s use simplifies both attribute and policy administration. HGABAC serves as the basis upon which extensions are built to incorporate delegation into ABAC. Several potential strategies for introducing delegation into ABAC are proposed, categorized into families and the trade-offs of each are examined. One such strategy is formalized into a new User-to-User Attribute Delegation model, built as an extension to the HGABAC model. Attribute Delegation enables users to delegate a subset of their attributes to other users in an off-line manner (not requiring connecting to a third party). Finally, a supporting architecture for HGABAC is detailed including descriptions of services, high-level communication protocols and a new low-level attribute certificate format for exchanging user and connection attributes between independent services. Particular emphasis is placed on ensuring support for federated and distributed systems. Critical components of the architecture are implemented and evaluated with promising preliminary results. It is hoped that the contributions in this research will further the acceptance of ABAC in both academia and industry by solving the problem of delegation as well as simplifying administration and policy authoring through the introduction of hierarchical user groups

    An Exploratory Study of the Influence of Design Process Ordering on the Requirement Generation of Novice Designers

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    In engineering design, the classic methodology of the design process encourages the problem definition to be developed prior to beginning concept generation. It is shown, however, that the problem definition and solutions must coevolve throughout the design process, each phase building off information learned from the other to develop in an iterative process. The current structuring of these steps leads to a disconnect between a final solution and the initial problem definition (often presented in the form design requirements). This research explores a methodology for improving the connection of design requirements to those final solutions through manipulation of the ordering of the design process. An experimental study was conducted to assess 104 engineering students’ requirements lists for a given design problem as they are influenced by developing requirements first versus sketching an initial concept prior to requirement generation. The control group was asked to generate requirements prior to sketching. The “sketch first” group was then asked to use their sketch to assist their requirement generation. Additionally, a second “sketch first” group was tested to determine the influence of being given explicit instructions to identify features of their sketch to further improve the requirements generated. It was found that this feature identification aspect of sketching leads to improved requirements lists based on the metrics of requirement quantity, variety, typology, completeness, and novelty, while simply changing the order of requirement generation and sketching had little or no effect. This indicates that the design process should explicitly connect a solution to the design requirements through formal instruction in order to improve the designers’ understanding of their goal

    Reservoir Computing in Materio

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    Reservoir Computing first emerged as an efficient mechanism for training recurrent neural networks and later evolved into a general theoretical model for dynamical systems. By applying only a simple training mechanism many physical systems have become exploitable unconventional computers. However, at present, many of these systems require careful selection and tuning by hand to produce usable or optimal reservoir computers. In this thesis we show the first steps to applying the reservoir model as a simple computational layer to extract exploitable information from complex material substrates. We argue that many physical substrates, even systems that in their natural state might not form usable or "good" reservoirs, can be configured into working reservoirs given some stimulation. To achieve this we apply techniques from evolution in materio whereby configuration is through evolved input-output signal mappings and targeted stimuli. In preliminary experiments the combined model and configuration method is applied to carbon nanotube/polymer composites. The results show substrates can be configured and trained as reservoir computers of varying quality. It is shown that applying the reservoir model adds greater functionality and programmability to physical substrates, without sacrificing performance. Next, the weaknesses of the technique are addressed, with the creation of new high input-output hardware system and an alternative multi-substrate framework. Lastly, a substantial effort is put into characterising the quality of a substrate for reservoir computing, i.e its ability to realise many reservoirs. From this, a methodological framework is devised. Using the framework, radically different computing substrates are compared and assessed, something previously not possible. As a result, a new understanding of the relationships between substrate, tasks and properties is possible, outlining the way for future exploration and optimisation of new computing substrates

    Observation-enhanced verification of operational processes

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    Operational processes are at the core of many organisations. The failure and misuse of these processes can cause significant economic losses to businesses or, in the worst cases, endanger human life. As a result, there has been significant research effort focused on the development of techniques and tools for the model-based analysis and verification of reliability, performance and quality-of-service properties of processes. Constructing models which accurately represent the behaviour of real-world systems is very challenging. The complexity and stochastic nature of real-world phenomena requires the use of modelling assumptions which introduce errors that can significantly impact the results of model-based analysis. Where inaccurate analyses are used as the basis of engineering or business decisions, the consequences can be catastrophic. Many operational processes are now routinely instrumented and capture information about component interactions and the behaviour of human operators. This thesis introduces a set of tool-supported techniques which exploit these logs in conjunction with tried and tested probabilistic model checking. This produces Markov models and formal analysis techniques which more accurately capture process behaviours and improve the quality of model-based analysis for operational processes. We show how observation data can be used to improve the modelling and analysis of continuous time systems by refining continuous-time Markov models (CTMCs) to more accurately reflect real-world behaviours. We apply the tools and techniques developed to real-world processes and demonstrate how we may avoid the invalid decisions which arise from traditional CTMC modelling and analysis techniques. We also show how observation-enhanced discrete time Markov models may be used to characterise the behaviour of users within an operational process. The self-adaptive role based access control approach we develop uses a formal definition of adaptation policies to identify potential threats in a real-world IT support system and mitigates risks to the system

    Self-Adaptive Role-Based Access Control for Business Processes

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    © 2017 IEEE. We present an approach for dynamically reconfiguring the role-based access control (RBAC) of information systems running business processes, to protect them against insider threats. The new approach uses business process execution traces and stochastic model checking to establish confidence intervals for key measurable attributes of user behaviour, and thus to identify and adaptively demote users who misuse their access permissions maliciously or accidentally. We implemented and evaluated the approach and its policy specification formalism for a real IT support business process, showing their ability to express and apply a broad range of self-adaptive RBAC policies
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