Automatic Generation of Minimal Cut Sets

A cut set is a collection of component failure modes that could lead to a system failure. Cut Set Analysis (CSA) is applied to critical systems to identify and rank system vulnerabilities at design time. Model checking tools have been used to automate the generation of minimal cut sets but are generally based on checking reachability of system failure states. This paper describes a new approach to CSA using a Linear Temporal Logic (LTL) model checker called BT Analyser that supports the generation of multiple counterexamples. The approach enables a broader class of system failures to be analysed, by generalising from failure state formulae to failure behaviours expressed in LTL. The traditional approach to CSA using model checking requires the model or system failure to be modified, usually by hand, to eliminate already-discovered cut sets, and the model checker to be rerun, at each step. By contrast, the new approach works incrementally and fully automatically, thereby removing the tedious and error-prone manual process and resulting in significantly reduced computation time. This in turn enables larger models to be checked. Two different strategies for using BT Analyser for CSA are presented. There is generally no single best strategy for model checking: their relative efficiency depends on the model and property being analysed. Comparative results are given for the A320 hydraulics case study in the Behavior Tree modelling language.Comment: In Proceedings ESSS 2015, arXiv:1506.0325

Improving accounting information system performance and achieving competitive advantage through effective it governance

University of Technology Sydney. Faculty of Business.Accounting information systems (AIS) are a vital technology-based asset for all organisations. The accounting information that is generated and distributed by these systems is essential for effective strategic decision making and achieving ongoing organisational benefits. The quality of the accounting information used for these decisions is reliant on the performance capabilities of the AIS. Prior research has identified a number of direct organisational benefits that can be obtained through effective IT governance, including improvements in the performance of organisational information systems such as AIS. This thesis expands upon prior literature by utilising the resource based view of the firm (RBV) to examine how competitive advantage is achieved via complex interactions between IT governance, AIS and other technology related capabilities and resources. The three types of IT governance mechanism - structural, procedural and relational – are assessed from a theoretical perspective in regards to their suitability to act as RBV resources or capabilities. While only relational mechanisms are found to possess the characteristics required of an RBV resource or capability, a review of recent RBV-framed IT governance research finds that many studies give little consideration to relational mechanisms and rely predominately upon the presence of structural and procedural mechanisms to assess IT governance performance. To confirm the significance of relational mechanisms of IT governance, this thesis tests the capacity for relational mechanisms of IT governance to contribute to competitive advantage through improving the performance of IT management capabilities and organisational AIS. Observations were collected via a survey of senior finance executives in Australian organisations and analysed using partial least squares structural equation modelling (PLS SEM). The results indicate that, under the direction and control of effective IT governance, IT management capabilities are able to improve accounting information system (AIS) performance and thereby achieve competitive advantage. Moderation analysis reveals that the level of competitive and technological pressure (environmental dynamism) alters the relationship between IT governance and competitive advantage. This finding suggests that IT governance not only acts as a higher order capability by directing and controlling the use of other organisational resources and capabilities, but may also be capable of acting dynamically to achieve competitive advantage through exploiting opportunities created by competitive and environmental pressures

Effects of Distance and Sex on Verbal Productivity and Anxiety

The present study was designed to determine whether physical distance between male and female interviewees and a female interviewer affected verbal productivity and anxiety level when interviewees discussed academic, social, and personal topics. The interview was conceptualized as an information-gathering interview. Crucial variables in such interviews are client participation and information flow. Client verbal productivity appears to be directly related to these variables, and was used as one dependent variable to measure the impact of distance on interviewee verbal behavior. A self-report measure of anxiety, the Fear Thermometer was used as a second dependent variable. The experimental distances used in this investigation were, 2 feet (.6m), 5 feet (1.5m), and 9 feet (2.7m). For purposes of this study, these distances were labeled close, intermediate, and far, respectively. It was hypothesized that an intermediate distance would result in decreased interviewee anxiety and increased verbal productivity when interviewees discussed personal topics. Results indicated that an intermediate distance did not result in increased verbal productivity, but did result in decreased interviewee anxiety level. Other significant effects were found for Fear Thermometer: (a) female interviewees reported higher anxiety levels than males across all condition, (b) interviewees reported less discomfort in the social-academic-personal topic sequence condition than they did in both the other two topic sequence conditions, (c) interviewees reported higher anxiety levels when discussing personal topics than when discussing academic topics, (d) female interviewees reported higher anxiety levels than males when discussing personal and academic topics. Significant effects for verbal productivity revealed were: (e) male interviewees talked longer than females across all conditions, (f) interviewees talked longer about academic topics than they did about both personal and social topics, and (g) interviewees talked longer as the interview progressed, regardless of topic order. Anxiety as measured by the Fear Thermometer was correlated with verbal productivity, r = -.49. Discussion includes possible theoretical explanations and limitations of the study, with implications for the initial interview

Can system of systems be given self-x requirement engineering capabilities?

System of Systems (SoS) are a relatively recent phenomenon and present a whole new set of challenges for systems engineers. The system elements of an SoS are often managed and operated in a predominantly independent manner, over widely distributed geographic locations and are subject to evolution with various rates of change. The goals of the SoS itself often change over time. One purpose of this paper is to survey the literature on requirements management issues that are brought to the fore as a result of these and other SoS characteristics. We then explore a vision of how the key artefacts of requirements engineering might need to evolve, together with their supporting tools and processes, in order to better support the development, operation and maintenance of SoS’s. The vision is inspired by the autonomic computing paradigm, in which computing systems are equipped with self-x capabilities – such as self-configuration and self-healing – in order to manage themselves. Rather than presenting a solution our purpose is to better understand the new requirements engineering capabilities that will be required for SoS

Oxidative Stress Resulting From Helicobacter pylori Infection Contributes to Gastric Carcinogenesis.

Helicobacter pylori is a gram-negative, microaerophilic bacterium that infects the stomach and can lead to, among other disorders, the development of gastric cancer. The inability of the host to clear the infection results in a chronic inflammatory state with continued oxidative stress within the tissue. Reactive oxygen species and reactive nitrogen species produced by the immune and epithelial cells damage the host cells and can result in DNA damage. H pylori has evolved to evoke this damaging response while blunting the host's efforts to kill the bacteria. This long-lasting state with inflammation and oxidative stress can result in gastric carcinogenesis. Continued efforts to better understand the bacterium and the host response will serve to prevent or provide improved early diagnosis and treatment of gastric cancer