A runtime file system checker protects file-system metadata integrity. It checks the consistency of file system update operations before they are committed to disk, thus preventing corrupted updates from reaching the disk. In this thesis, we describe our experiences with building Brunch, a runtime checker for an emerging Linux file system called Btrfs. Btrfs supports many modern file-system features that pose challenges in designing a robust checker. We find that the runtime consistency checks need to be expressed clearly so that they can be reasoned about and implemented reliably, and thus we propose writing the checks declaratively. This approach reduces the complexity of the checks, ensures their independence, and helps identify the correct abstractions in the checker. It also shows how the checker can be designed to handle arbitrary file system corruption. Our results show that runtime consistency checking is still viable for complex, modern file systems.

This paper is about save systems and will analyze save functions in various games. Save systems in games are usually blamed for harming the suspension of disbelief as it is an act taking place outside the game and should only be used for its intended purpose: letting the players store their game data, and progress whenever they need. The game save function developed as rapid leaps of technology were made, with the beginning era of home consoles and home computers allowing players to spend more time playing, creating a demand for longer play sessions in games which lead to a need of methods for storing game data. The analysis of save systems is carried out in this paper by using MDA Framework (Mechanics, Dynamics, Aesthetics), a tool used for documenting game design. This framework can be used to analyze a game from a designer‟s or player‟s perspective. By reversing the framework ADM (Aesthetics, Dynamics and Mechanics) one can analyze the user experience, which is how the player perceives the game‟s aesthetics to be, depending on the dynamics and mechanics. This analysis aims to provide knowledge of how consistency in game design and the save system can be used to create a cohesive game world that facillitates the player's experience and immersion.

Information delivery via the web has become very popular. Along with a growing user population, systems increasingly are supporting content that changes frequently, personalised information, and differentiation and choice. This thesis is concerned with the design and evaluation of resource management strategies for such systems. An architecture that provides scalability through caching proxies is considered. When a cached page is updated at the server, the cached copy may become stale if the server is not able to transmit the update to the proxies immediately. From the perspective of the server, resources are required to transmit updates for cached pages and to process requests for pages that are not cached. Analytic results on how the available resources should be managed in order to minimise staleness-related cost are presented. An efficient algorithm that the server can use to determine the set of pages that should be cached and a policy for transmitting updates for these pages are also presented. We then apply these results to page fragments, a technique that can provide increased efficiency for delivery of personalised pages.

New emission legislations introduced in the European Union and the U.S. have made truck manufacturers face stricter requirements for low emissions and on-board diagnostic systems. The on-board diagnostic system typically consists of several tests that are run when the truck is driving. One way to construct such tests is to use so called consistency relations. A consistency relation is a relation with known variables that in the fault free case always holds. Calculation of a consistency relation typically involves eliminating unknown variables from a set of equations. To eliminate variables from a differential polynomial system, methods from differential algebra can be used. In this thesis, the purely algebraic Gröbner basis algorithm and the differential Rosenfeld-Gröbner algorithm implemented in the Maple package Diffalg have been compared and evaluated. The conclusion drawn is that there are no significant differences between the methods. However, since using Gröbner basis requires differentiations to be made in advance, the recommendation is to use the Rosenfeld-Gröbner algorithm. Further, attempts to calculate consistency relations using the Rosenfeld-Gröbner algorithm have been made to a real application, a model of a Scania diesel engine. These attempts did not yield any successful results. It was only possible to calculate one consistency relation. This can be explained by the high complexity of the model.

Information delivery via the web has become very popular. Along with a growing user population, systems increasingly are supporting content that changes frequently, personalised information, and differentiation and choice. This thesis is concerned with the design and evaluation of resource management strategies for such systems. An architecture that provides scalability through caching proxies is considered. When a cached page is updated at the server, the cached copy may become stale if the server is not able to transmit the update to the proxies immediately. From the perspective of the server, resources are required to transmit updates for cached pages and to process requests for pages that are not cached. Analytic results on how the available resources should be managed in order to minimise staleness-related cost are presented. An efficient algorithm that the server can use to determine the set of pages that should be cached and a policy for transmitting updates for these pages are also presented. We then apply these results to page fragments, a technique that can provide increased efficiency for delivery of personalised pages.

Research where personality in animals is studied is becoming more and more common. In this area there are different concepts like behavioural syndrome and animal personality and they usually talk about consistency in behaviour over time and situations. This consistent individual behaviour can be used as an indicator of how individuals can handle and adjust to new situations in the environment. Because of this, personality studies in animals are very important in animal welfare. In this study personality in dairy cattle in lose housing were studied. 28 cows of the breeds Swedish black and white cattle (SLB) and Swedish red and white cattle (SRB) was studied during three observation situations (milking, undisturbed behaviour and novel object). With the help of Principal component analysis four components that together explained 72% of the variation in data were found. The two first components could then be interpreted. The first component corresponds to the dimension extraversion in the”Big five” model that is used in personality studies in humans. The second component was the opposite of the first one, which means that it showed low activity and low sociability. This low activity could indicate fear dependent on why the cows were standing so much. T-tests only showed significant differences in the behaviour based on the age of the cows, which indicates that the personality trait becomes more typical with higher age. The conclusion is that there are individual differences in dairy cattle which could be interpreted as personality traits.

This dissertation consists of two essays in international macroeconomics. The first essay shows that optimal fiscal and monetary policy is time consistent in a standard small open economy. Further, there exist many maturity structures of public debt capable of rendering the optimal policy time consistent. This result is in sharp contrast with that obtained in the context of closed-economy models. In the closed economy, the time consistency of optimal monetary and fiscal policy imposes severe restrictions on public debt in the form of a unique term structure of public debt that governments can leave to their successors at each point in time. The time consistent result is robust: optimal policy is time consistent when both real and nominal bonds have finite horizons. While in a closed economy, governments must have both nominal and real bonds, and have at least real bonds over an infinite horizon to render optimal policy time consistent. The second essay uses a dynamic stochastic general equilibrium model to theoretically rationalize the empirical finding that sudden stops have weaker effects on outputs when the small open economy is more open to trade. First, welfare costs of sudden stops are decreasing in trade openness. The reason is that when the economy is more open to trade, the economy will have less volatile capital, which leads to less volatile output. In terms of welfare, when the small open economy is more open to trade, the welfare costs of sudden stops will be smaller. Second, sudden stops may be welfare improving to the small open economy. This is because when the representative household is a net borrower in the international capital market, its consumption will be negatively correlated with country spread. Since utility is a concave function of consumption, it must be a convex function of country spread. That is, when the country spread is more volatile, the mean utility is higher. The two findings are robust: they hold with one sector economy model, and two sector economy models with homogenous capital and heterogenous capital. In addition, this paper shows that a counter-cyclical tariff rate policy is not welfare-improving. / Dissertation

As computers become pervasive in environments that include the home and community, new applications are emerging that will create and manipulate sensitive and private information. These applications span systems ranging from personal to mobile and hand held devices. They would benefit from a data storage service that protects the integrity and confidentiality of the stored data and is highly available. Such a data repository would have to meet the needs of a variety of applications, handling data with varying security and performance requirements. Providing simultaneously both high levels of security and high levels of performance may not be possible when many nodes in the system are under attack. The agility approach to building secure distributed services advocates the principle that the overhead of providing strong security guarantees should be incurred only by those applications that require such high levels of security and only at times when it is necessary to defend against high threat levels. A storage service that is designed for a variety of applications must follow the principles of agility, offering applications a range of options to choose from for their security and performance requirements. This research presents secure store, a secure and highly available distributed store to meet the performance and security needs of a variety of applications. Secure store is designed to guarantee integrity, confidentiality and availability of stored data even in the face of limited number of compromised servers. Secure store is designed based on the principles of agility. Secure store integrates two well known techniques, namely replication and secret-sharing, and exploits the tradeoffs that exist between security and performance to offer applications a range of options to choose from to suit their needs. This thesis makes several contributions, including (1) illustration of the the principles of agility, (2) a novel gossip-style secure dissemination protocol whose performance is comparable to the best-possible benign-case protocol in the absence of any malicious activity, (3) demonstration of the performance benefits of using weaker consistency models for data access, and (4) a technique called collective endorsement that can be used in other secure distributed applications.

Regularity is a shared memory consistency condition that has received considerable attention, notably in connection with quorum-based shared memory. Lamport's original definition of regularity assumed a single-writer model, however, and is not well defined when each shared variable may have multiple writers. In this thesis, we address this need by formally extending the notion of regularity to a multi-writer model. We have shown that the extension is not trivial. While there exist various ways to extend the single-writer definition, the resulting definitions will have different strengths. Specifically, we give several possible definitions of regularity in the presence of multiple writers. We then present a quorum-based algorithm to implement each of the proposed definitions and prove them correct. We study the relationships between these definitions and a number of other well-known consistency conditions, and give a partial order describing the relative strengths of these consistency conditions. Finally, we provide a practical context for our results by studying the correctness of two well-known algorithms for mutual exclusion under each of our proposed consistency conditions.

This paper studies the quality of mandatory financial forecasts which announced by Taiwan lists and OTC companies ¡]hereinafter called ¡§the companies¡¨¡^. Does outside financial analyst can offer the public users more useful financial forecast than the companies¡H What¡¦s the difference on precision between financial forecasts issued from the companies and outside analysts¡HBesides, this paper also tests if the companies would perform earnings management for meeting the public expectation. The empirical results indicate that for public investors, the mandatory financial forecasts issued by the companies didn¡¦t show better accrual precision than the financial forecast issued by outside analysts. There wasn¡¦t any significant difference on degree of differential between financial forecast prepared by outside analysts and the companies. The risk for using both of the financial forecasts are the same. That means the investors can rely on none of the companies and outside analysts¡¦ forecasts to do investment decision. And the companies performed earning management to meet the consistent expectation of earning arose from market which can avoid the bad result when the actual financial report differ from forecast. In summary, the mandatory financial forecasts in Taiwan can not offer timely useful information to investors. Most of them only increase the preparation cost and control cost. Some of the companies even use them as the tool to collect money from public for personal welfare. We recommend the government authorities to consider the benefit of voluntary financial forecast system in UAS when they are reviewing the mandatory financial forecast system. The voluntary financial forecast system may solve the problems of incomplete predictability of financial forecast and asymmetry of information, finally increase the usefulness of financial forecasts.