Automated Validation of State-Based Client-Centric Isolation with TLA ⁺

Clear consistency guarantees on data are paramount for the design and implementation of distributed systems. When implementing distributed applications, developers require approaches to verify the data consistency guarantees of an implementation choice. Crooks et al. define a state-based and client-centric model of database isolation. This paper formalizes this state-based model in, reproduces their examples and shows how to model check runtime traces and algorithms with this formalization. The formalized model in enables semi-automatic model checking for different implementation alternatives for transactional operations and allows checking of conformance to isolation levels. We reproduce examples of the original paper and confirm the isolation guarantees of the combination of the well-known 2-phase locking and 2-phase commit algorithms. Using model checking this formalization can also help finding bugs in incorrect specifications. This improves feasibility of automated checking of isolation guarantees in synthesized synchronization implementations and it provides an environment for experimenting with new designs.</p

Portmerion, Proportion and Perspective

The holiday village of Portmerion was created by Bertram Clough Williams-Ellis (1883 1978) over a period of fifty-one years, starting in 1926. It was grade II listed in 1971. However, Portmerion has become a part of western popular culture rather than of mainstream architectural history. Its use as the setting for the cult 1967 television series “The Prisoner” ensures continued worldwide interest and a constant stream of visitors. Williams Ellis’ design methods were empirical, initial designs being adjusted by eye on site in close collaboration with trusted builders. This paper analyses the development of Portmerion as a gesamtkunstwerk; considering the experience of movement through the village as a dynamic composition of shifting vistas, focussing the visitor on a series of constructed views. Through this analysis, Portmerion is revealed as both a manifestation of the architecture of pleasure and an exercise in the pleasure of architecture

Attitudes of Students and Practitioners Regarding Ethical Acceptability of Accounting Transactions

This study reports the findings of a study assessing the acceptability differences in decisions made by Certified Public Accounting practitioners (CPA) and students studying to become CPAs. The study responds to researchers’ call for additional research on topics related to accounting decision ethics. Modified managerial and accounting recognition scenarios were used to collect the acceptability of ethical judgments. The analysis employs factor analysis to affirm whether the scenarios are mana­gerial or accounting recognition decisions. The analyses further divides the managerial decisions into either revenue or expense related. The accounting recognition decisions are further divided into those involving an accounting manipulation or inventory related. Students’ acceptability of the accounting transactions was far harsher than the practitioners. However, both students and practitioners considered the accounting scenarios to be unethical. Both students and practitioners judged the managerial revenue scenarios to be ethical but the managerial expense scenarios to be moderately unethical. In addition to the ethical acceptability of accounting transaction, student and practitioner demographic data including age, work experience and academic credentials are investigated to explain the differences

Design and Control of a Two-Wheeled Robotic Walker

This thesis presents the design, construction, and control of a two-wheeled inverted pendulum (TWIP) robotic walker prototype for assisting mobility-impaired users with balance and fall prevention. A conceptual model of the robotic walker is developed and used to illustrate the purpose of this study. A linearized mathematical model of the two-wheeled system is derived using Newtonian mechanics. A control strategy consisting of a decoupled LQR controller and three state variable controllers is developed to stabilize the platform and regulate its behavior with robust disturbance rejection performance. Simulation results reveal that the LQR controller is capable of stabilizing the platform and rejecting external disturbances while the state variable controllers simultaneously regulate the system’s position with smooth and minimum jerk control. A prototype for the two-wheeled system is fabricated and assembled followed by the implementation and tuning of the control algorithms responsible for stabilizing the prototype and regulating its position with optimal performance. Several experiments are conducted, confirming the ability of the decoupled LQR controller to robustly balance the platform while the state variable controllers regulate the platform’s position with smooth and minimum jerk control