Semantics and Verification of UML Activity Diagrams for Workflow Modelling

This thesis defines a formal semantics for UML activity diagrams that is suitable for workflow modelling. The semantics allows verification of functional requirements using model checking. Since a workflow specification prescribes how a workflow system behaves, the semantics is defined and motivated in terms of workflow systems. As workflow systems are reactive and coordinate activities, the defined semantics reflects these aspects. In fact, two formal semantics are defined, which are completely different. Both semantics are defined directly in terms of activity diagrams and not by a mapping of activity diagrams to some existing formal notation. The requirements-level semantics, based on the Statemate semantics of statecharts, assumes that workflow systems are infinitely fast w.r.t. their environment and react immediately to input events (this assumption is called the perfect synchrony hypothesis). The implementation-level semantics, based on the UML semantics of statecharts, does not make this assumption. Due to the perfect synchrony hypothesis, the requirements-level semantics is unrealistic, but easy to use for verification. On the other hand, the implementation-level semantics is realistic, but difficult to use for verification. A class of activity diagrams and a class of functional requirements is identified for which the outcome of the verification does not depend upon the particular semantics being used, i.e., both semantics give the same result. For such activity diagrams and such functional requirements, the requirements-level semantics is as realistic as the implementation-level semantics, even though the requirements-level semantics makes the perfect synchrony hypothesis. The requirements-level semantics has been implemented in a verification tool. The tool interfaces with a model checker by translating an activity diagram into an input for a model checker according to the requirements-level semantics. The model checker checks the desired functional requirement against the input model. If the model checker returns a counterexample, the tool translates this counterexample back into the activity diagram by highlighting a path corresponding to the counterexample. The tool supports verification of workflow models that have event-driven behaviour, data, real time, and loops. Only model checkers supporting strong fairness model checking turn out to be useful. The feasibility of the approach is demonstrated by using the tool to verify some real-life workflow models

Seeking the Leviathan, the General Will and the Invisible Hand in Rural Guinea, West Africa: A Science of Human Nature

The dissertation builds a bridge from the social-philosophical works of Hobbes, Rousseau, and Smith to current game theoretical models explaining social order to two empirical applications in a rural region of Guinea. The work focuses on the central role of natural resources for human societies and uses two empirical studies to test general hypotheses on the drivers of the sustainable exploitation and the equitable distribution of natural resources. The work strictly follows a quantitative empirical approach. After discussing the methodological foundations of statistical causal analysis in a first step, the various approaches are evaluated in a simulation study. Finally, the most successful of these approaches finds its application in the analysis of the empirical data, which was collected during field research in Guinea. In the observational study, socioeconomic data are combined with environmental data to model the influence of humans on the occurrence of wild species that are exploited for economic purposes in the study area. In the experimental study, socioeconomic data is linked to experimental data from a resource distribution game to identify factors affecting the people’s behavior when sharing a common natural resource. Both the exploitation of wild species and the sharing of a natural resource show that the social context is crucial for the understanding of human behavior, as postulated by Hobbes, Rousseau, and Smith: reputation, market integration, inequality and homogeneity of the population, as well as the salience of moral norms and property rights are essential dimensions.Die Dissertation widmet sich der zentralen Rolle von natürlichen Ressourcen für menschliche Gesellschaften. Anhand zweier empirischer Studien werden allgemeine Hypothesen zu den Determinanten der nachhaltigen Ausbeutung und gerechten Verteilung von natürlichen Ressourcen getestet. Dabei wird in der Arbeit eine Brücke von den Werken der Sozialphilosophen Hobbes, Rousseau und Smith, über aktuelle spieltheoretische Modelle zur Erklärung sozialer Ordnung, hin zu zwei empirischen Anwendungen in einer ländlichen Region Guineas geschlagen. Die Arbeit folgt strikt einem empirischen quantitativen Ansatz. Nach der Erörterung der methodischen Grundlagen der statistischen Kausalanalyse werden die verschiedenen Ansätze im Rahmen einer Simulationsstudie evaluiert. Schließlich findet der erfolgreichste dieser Ansätze in der Auswertung der Daten, die bei der Feldforschung in Guinea erhoben wurden, Anwendung. In der Beobachtungsstudie werden sozioökonomische Daten mit ökologischen Daten verknüpft, um den Einfluss der Menschen auf das Vorkommen von wilden Arten, die zu ökonomischen Zwecken ausgebeutet werden, im Untersuchungsgebiet zu modellieren. In der Experimentalstudie werden sozioökonomische Daten mit Experimentaldaten aus einem Ressourcenverteilungsspiel verknüpft, um Faktoren zu identifizieren, welche sich auf das Verhalten von Menschen beim Teilen einer gemeinsamen natürlichen Ressource auswirken. Sowohl für die Ausbeutung der wilden Arten, wie auch für das gemeinsame Teilen einer natürlichen Ressource gilt, dass der soziale Kontext für das Verhalten der Menschen von großer Relevanz ist, wie von Hobbes, Rousseau und Smith postuliert: Reputation, Marktintegration, Ungleichheit und Homogenität der Bevölkerung sowie die Salienz moralischer Normen und Eigentumsrechte sind entscheidende Dimensionen

Seeking the Leviathan, the General Will and the Invisible Hand in Rural Guinea, West Africa: A Science of Human Nature

The dissertation builds a bridge from the social-philosophical works of Hobbes, Rousseau, and Smith to current game theoretical models explaining social order to two empirical applications in a rural region of Guinea. The work focuses on the central role of natural resources for human societies and uses two empirical studies to test general hypotheses on the drivers of the sustainable exploitation and the equitable distribution of natural resources. The work strictly follows a quantitative empirical approach. After discussing the methodological foundations of statistical causal analysis in a first step, the various approaches are evaluated in a simulation study. Finally, the most successful of these approaches finds its application in the analysis of the empirical data, which was collected during field research in Guinea. In the observational study, socioeconomic data are combined with environmental data to model the influence of humans on the occurrence of wild species that are exploited for economic purposes in the study area. In the experimental study, socioeconomic data is linked to experimental data from a resource distribution game to identify factors affecting the people’s behavior when sharing a common natural resource. Both the exploitation of wild species and the sharing of a natural resource show that the social context is crucial for the understanding of human behavior, as postulated by Hobbes, Rousseau, and Smith: reputation, market integration, inequality and homogeneity of the population, as well as the salience of moral norms and property rights are essential dimensions.Die Dissertation widmet sich der zentralen Rolle von natürlichen Ressourcen für menschliche Gesellschaften. Anhand zweier empirischer Studien werden allgemeine Hypothesen zu den Determinanten der nachhaltigen Ausbeutung und gerechten Verteilung von natürlichen Ressourcen getestet. Dabei wird in der Arbeit eine Brücke von den Werken der Sozialphilosophen Hobbes, Rousseau und Smith, über aktuelle spieltheoretische Modelle zur Erklärung sozialer Ordnung, hin zu zwei empirischen Anwendungen in einer ländlichen Region Guineas geschlagen. Die Arbeit folgt strikt einem empirischen quantitativen Ansatz. Nach der Erörterung der methodischen Grundlagen der statistischen Kausalanalyse werden die verschiedenen Ansätze im Rahmen einer Simulationsstudie evaluiert. Schließlich findet der erfolgreichste dieser Ansätze in der Auswertung der Daten, die bei der Feldforschung in Guinea erhoben wurden, Anwendung. In der Beobachtungsstudie werden sozioökonomische Daten mit ökologischen Daten verknüpft, um den Einfluss der Menschen auf das Vorkommen von wilden Arten, die zu ökonomischen Zwecken ausgebeutet werden, im Untersuchungsgebiet zu modellieren. In der Experimentalstudie werden sozioökonomische Daten mit Experimentaldaten aus einem Ressourcenverteilungsspiel verknüpft, um Faktoren zu identifizieren, welche sich auf das Verhalten von Menschen beim Teilen einer gemeinsamen natürlichen Ressource auswirken. Sowohl für die Ausbeutung der wilden Arten, wie auch für das gemeinsame Teilen einer natürlichen Ressource gilt, dass der soziale Kontext für das Verhalten der Menschen von großer Relevanz ist, wie von Hobbes, Rousseau und Smith postuliert: Reputation, Marktintegration, Ungleichheit und Homogenität der Bevölkerung sowie die Salienz moralischer Normen und Eigentumsrechte sind entscheidende Dimensionen

Game Theory Relaunched

The game is on. Do you know how to play? Game theory sets out to explore what can be said about making decisions which go beyond accepting the rules of a game. Since 1942, a well elaborated mathematical apparatus has been developed to do so; but there is more. During the last three decades game theoretic reasoning has popped up in many other fields as well - from engineering to biology and psychology. New simulation tools and network analysis have made game theory omnipresent these days. This book collects recent research papers in game theory, which come from diverse scientific communities all across the world; they combine many different fields like economics, politics, history, engineering, mathematics, physics, and psychology. All of them have as a common denominator some method of game theory. Enjoy

Sustaining off-reserve forests in Ghana: a game-theoretic approach

This thesis explores options for resolving the ongoing tenure and compensation conflicts in the off-reserve forests (non-plantation forests outside permanent forest reserves) in Ghana. The ongoing degradation of the forests has been attributed to the prevalent tenure and compensation conflicts among cocoa farmers, the government, and logging concessionaires. Cocoa farmers nurture and preserve naturally growing trees in the off-reserve forests. They even plant indigenous tree species on their farms for the purpose of providing additional shades for their cocoa crops. Yet since 1998, the government has denied farmers any legal rights to the shade trees they retain on their farms. In addition, crops are extensively damaged by logging and transporting activities occurring on cocoa farms. However, most concessionaires fail to adequately compensate affected farmers. Farmers tend to resort to unsustainable forest practices as a result of these tenure and compensation conflicts. They markedly reduce shade tree density when cocoa crops start bearing pods by cutting down or killing many young trees and engaging in illegal (chainsaw) logging. Thus, the key research question investigated by this thesis is: what is the most optimal policy option for minimising unsustainable forest practices among farmers? To respond to this question, this thesis developed game-theoretic models to predict the future behaviour of some key stakeholders under hypothetical policy scenarios. The predictions of the game-theoretic models were then tested with empirical data collected from farmers and concessionaires in Ghana in 2016. The current behaviours of the concessionaires and farmers in the off-reserve forests were found to be consistent with the rational-choice model. These stakeholders are behaving in ways that will maximise their expected values in the off-reserve forests. Both the theoretical and empirical results revealed that farmers are less likely to be fully compensated should they pursue compensation on their own. It was found that a credible threat of litigation by a third-party advocate is likely to be the most optimal option to ensure that concessionaires fully and promptly compensate farmers for crop damage. More importantly, the most optimal policy option to motivate farmers to increase tree density and diversity and minimise farmer-driven illegal logging is a policy mix that concurrently provides 40% of stumpage revenue to farmers; ensures full compensation for crop damage through third-party litigation; and strictly enforces the tree harvesting rule using FC-farmer partnerships.Thesis (Ph.D.) -- University of Adelaide, School of Social Sciences, 201

Strategic interdependence, hypothetical bargaining, and mutual advantage in non-cooperative games

One of the conceptual limitations of the orthodox game theory is its inability to offer definitive theoretical predictions concerning the outcomes of noncooperative games with multiple rationalizable outcomes. This prompted the emergence of goal-directed theories of reasoning – the team reasoning theory and the theory of hypothetical bargaining. Both theories suggest that people resolve non-cooperative games by using a reasoning algorithm which allows them to identify mutually advantageous solutions of non-cooperative games. The primary aim of this thesis is to enrich the current debate on goaldirected reasoning theories by studying the extent to which the principles of the bargaining theory can be used to formally characterize the concept of mutual advantage in a way which is compatible with some of the conceptually compelling principles of orthodox game theory, such as individual rationality, incentive compatibility, and non-comparability of decision-makers’ personal payoffs. I discuss two formal characterizations of the concept of mutual advantage derived from the aforementioned goal-directed reasoning theories: A measure of mutual advantage developed in collaboration with Jurgis Karpus, which is broadly in line with the notion of mutual advantage suggested by Sugden (2011, 2015), and the benefit-equilibrating bargaining solution function, which is broadly in line with the principles underlying Conley and Wilkie’s (2012) solution for Pareto optimal point selection problems with finite choice sets. I discuss the formal properties of each solution, as well as its theoretical predictions in a number of games. I also explore each solution concept’s compatibility with orthodox game theory. I also discuss the limitations of the aforementioned goal-directed reasoning theories. I argue that each theory offers a compelling explanation of how a certain type of decision-maker identifies the mutually advantageous solutions of non-cooperative games, but neither of them offers a definitive answer to the question of how people coordinate their actions in non-cooperative social interactions

Creationism and evolution

In Tower of Babel, Robert Pennock wrote that “defenders of evolution would help their case immeasurably if they would reassure their audience that morality, purpose, and meaning are not lost by accepting the truth of evolution.” We first consider the thesis that the creationists’ movement exploits moral concerns to spread its ideas against the theory of evolution. We analyze their arguments and possible reasons why they are easily accepted. Creationists usually employ two contradictive strategies to expose the purported moral degradation that comes with accepting the theory of evolution. On the one hand they claim that evolutionary theory is immoral. On the other hand creationists think of evolutionary theory as amoral. Both objections come naturally in a monotheistic view. But we can find similar conclusions about the supposed moral aspects of evolution in non-religiously inspired discussions. Meanwhile, the creationism-evolution debate mainly focuses — understandably — on what constitutes good science. We consider the need for moral reassurance and analyze reassuring arguments from philosophers. Philosophers may stress that science does not prescribe and is therefore not immoral, but this reaction opens the door for the objection of amorality that evolution — as a naturalistic world view at least — supposedly endorses. We consider that the topic of morality and its relation to the acceptance of evolution may need more empirical research