Künstliche Intelligenz und selbst-lernende Systeme, die ihr Verhalten aufgrund vergangener Entscheidungen und historischer Daten adaptieren, spielen eine im- mer größer werdende Rollen in unserem Alltag. Wir sind umgeben von einer großen Zahl algorithmischer Entscheidungshilfen, sowie einer stetig wachsenden Zahl algorithmischer Entscheidungssysteme. Rankings und sortierte Listen von Suchergebnissen stellen dabei das wesentliche Instrument unserer Onlinesuche nach Inhalten, Produkten, Freizeitaktivitäten und relevanten Personen dar. Aus diesem Grund bestimmt die Reihenfolge der Suchergebnisse nicht nur die Zufriedenheit der Suchenden, sondern auch die Chancen der Sortierten auf Bildung, ökonomischen und sogar sozialen Erfolg. Wissenschaft und Politik sorgen sich aus diesem Grund mehr und mehr um systematische Diskriminierung und Bias durch selbst-lernende Systeme. Um der Diskriminierung im Kontext von Rankings und sortierten Suchergeb- nissen Herr zu werden, sind folgende drei Probleme zu addressieren: Zunächst müssen wir die ethischen Eigenschaften und moralischen Ziele verschiedener Sit- uationen erarbeiten, in denen Rankings eingesetzt werden. Diese sollen mit den ethischen Werten der Algorithmen übereinstimmen, die zur Vermeidung von diskri- minierenden Rankings Anwendung finden. Zweitens ist es notwendig, ethische Wertesysteme in Mathematik und Algorithmen zu übersetzen, um sämtliche moralis- chen Ziele bedienen zu können. Drittens sollten diese Methoden einem breiten Publikum zugänglich sein, das sowohl Programmierer:innen, als auch Jurist:innen und Politiker:innen umfasst. / Artificial intelligence and adaptive systems, that learn patterns from past behavior and historic data, play an increasing role in our day-to-day lives. We are surrounded by a vast amount of algorithmic decision aids, and more and more by algorithmic decision making systems, too. As a subcategory, ranked search results have become the main mechanism, by which we find content, products, places, and people online. Thus their ordering contributes not only to the satisfaction of the searcher, but also to career and business opportunities, educational placement, and even social success of those being ranked. Therefore researchers have become increasingly concerned with systematic biases and discrimination in data-driven ranking models. To address the problem of discrimination and fairness in the context of rank- ings, three main problems have to be solved: First, we have to understand the philosophical properties of different ranking situations and all important fairness definitions to be able to decide which method would be the most appropriate for a given context. Second, we have to make sure that, for any fairness requirement in a ranking context, a formal definition that meets such requirements exists. More concretely, if a ranking context, for example, requires group fairness to be met, we need an actual definition for group fairness in rankings in the first place. Third, the methods together with their underlying fairness concepts and properties need to be available to a wide range of audiences, from programmers, to policy makers and politicians.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Don Gruenbacher / Caterina Scoglio / In this dissertation, we investigate research gaps still existing in P2P file-sharing systems: the necessity of fairness maintenance during the content information publishing/retrieving process, and the stranger policies on P2P fairness. First, through a wide range of measurements in the KAD network, we present the impact of a poorly designed incentive fairness policy on the performance of looking up content information. The KAD network, designed to help peers publish and retrieve sharing information, adopts a distributed hash table (DHT) technology and combines itself into the aMule/eMule P2P file-sharing network. We develop a distributed measurement framework that employs multiple test nodes running on the PlanetLab testbed. During the measurements, the routing tables of around 20,000 peers are crawled and analyzed. More than 3,000,000 pieces of source location information from the publishing tables of multiple peers are retrieved and contacted. Based on these measurements, we show that the routing table is well maintained, while the maintenance policy for the source-location-information publishing table is not well designed. Both the current maintenance schedule for the publishing table and the poor incentive policy on publishing peers eventually result in the low availability of the publishing table, which accordingly cause low lookup performance of the KAD network. Moreover, we propose three possible solutions to address these issues: the self-maintenance scheme with short period renewal interval, the chunk-based publishing/retrieving scheme, and the fairness scheme. Second, using both numerical analyses and agent-based simulations, we evaluate the impact of different stranger policies on system performance and fairness. We explore that the extremely restricting stranger policy brings the best fairness at a cost of performance degradation. The varying tendency of performance and fairness under different stranger policies are not consistent. A trade-off exists between controlling free-riding and maintaining system performance. Thus, P2P designers are required to tackle strangers carefully according to their individual design goals. We also show that BitTorrent prefers to maintain fairness with an extremely restricting stranger policy, while aMule/eMule’s fully rewarding stranger policy promotes free-riders’ benefit.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Balasubramaniam Natarajan / With the explosive growth of wireless systems and services, bandwidth has become a treasured commodity. Traditionally, licensed frequency bands were exclusively reserved for use by the primary license holders (primary users), whereas, unlicensed frequency bands allow spectrum sharing. Recent spectrum measurements indicate that many licensed bands remain relatively unused for most of the time. Therefore, allowing secondary users (users without a license to operate in the band) to operate with minimal or no interference to primary users is one way of sharing spectrum to increase efficiency. Recently, Federal Communications Commission (FCC) has opened up licensed bands for opportunistic use by secondary users. A cognitive radio (CR) is one enabling technology for systems supporting opportunistic use. A cognitive radio adapts to the environment it operates in by sensing the spectrum and quickly decides on appropriate frequency bands and transmission parameters to use in order to achieve certain performance goals. A cognitive radio network (CRN) refers to a network of cognitive radios/secondary users. In this dissertation, we consider a competitive CRN with multiple channels available for opportunistic use by multiple secondary users. We also assume that multiple secondary users may coexist in a channel and each secondary user (SU) can use multiple channels to satisfy their rate requirements. In this context, firstly, we introduce an integrated modeling and forecasting tool that provides an upper bound estimate of the number of secondary users that may be demanding access to each of the channels at the next instant. Assuming a continuous time Markov chain model for both primary and secondary users activities, we propose a Kalman filter based approach for estimating the number of primary and secondary users. These estimates are in turn used to predict the number of primary and secondary users in a future time instant. We extend the modeling and forecasting framework to the case when SU traffic is governed by Erlangian process. Secondly, assuming that scheduling is complete and SUs have identified the channels to use, we propose two quality of service (QoS) constrained resource allocation frameworks. Our measures for QoS include signal to interference plus noise ratio (SINR) /bit error rate (BER) and total rate requirement. In the first framework, we determine the minimum transmit power that SUs should employ in order to maintain a certain SINR and use that result to calculate the optimal rate allocation strategy across channels. The rate allocation problem is formulated as a maximum flow problem in graph theory. We also propose a simple heuristic to determine the rate allocation. In the second framework, both transmit power and rate per channel are simultaneously optimized with the help of a bi-objective optimization problem formulation. Unlike prior efforts, we transform the BER requirement constraint into a convex constraint in order to guarantee optimality of resulting solutions. Thirdly, we borrow ideas from social behavioral models such as Homo Egualis (HE), Homo Parochius (HP) and Homo Reciprocan (HR) models and apply it to the resource management solutions to maintain fairness among SUs in a competitive CRN setting. Finally, we develop distributed user-based approaches based on ``Dual Decomposition Theory" and ``Game Theory" to solve the proposed resource allocation frameworks. In summary, our body of work represents significant ground breaking advances in the analysis of competitive CRNs.

The design of incentive compensation plans is critical to a company’s success. This study develops and validates a theoretical model to examine how incentive contract framing affects effort. This study uses an experiment to observe the effect of the manipulation of incentive contract frame and the presence or absence of principal discretion in performance evaluation on effort. The results of the experiment show that when principal discretion in performance evaluation is absent, penalty contracts induce greater effort than bonus contracts. The results of the experiment also demonstrate that the interaction of principal discretion in performance evaluation and contract frame influences how agents view the perceived fairness of their incentive contract. Specifically, principal discretion in performance evaluation increases perceived fairness under a penalty contract but not under a bonus contract. This study also extends prior research by documenting that perceived fairness explains how incentive contract frame affects trust and effort.

Thesis (DTh)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This thesis is a critical study of the work of John Rawls, political philosopher, and Reinhold Niebuhr, theologian. The work of these two scholars is brought into dialogue with theological thought to work towards a Christian notion of justice which seeks more than justice as fairness but realises the impossibility of perfect love in this world. Rawls’s two principles of justice form the basis of the discussion, with liberty placed prior to equality, and permissible inequalities only allowed when the weakest benefit. He excludes religion and moral reasoning from justice, essentially any thick theory of the good, in favour of the right; any conception of the good must be in agreement with the right and a thin theory of the good is necessary to guide people in the right direction. In his later works he accepts that people will mostly be guided by some moral or religious thought. Niebuhr believed that a prophetic religion combines an utmost seriousness about history with a transcendent norm. Hope, faith and love form the foundation of a call to a continual struggle for justice and equality. The boundaries in which justice is sought are being continually extended as global cooperation and dependence increase. Perfect justice would be a state of solidarity with no conflict of interests. Because people are a combination of vitality and reason, the social coherence of life can never be based on pure rationality. Our truth is never the truth; we are always subjective and prejudiced. There can be no universal rational standards of justice or neutrality in social struggle. Love is the primary law of nature and a fundamental requirement of social existence. We are called to involvement in society by the very nature of our justification by faith. Equality as the pinnacle of the ideal of justice points towards love as the final norm of justice; for equal justice is the realization of community under the conditions of sin. Justice as imperfect love aims for an equality which is increasingly inclusive and continuously creates space for people to live in harmony. In the final chapter, Rawls and Niebuhr are brought into critical discussion with other theologians. The Christian preference for the poor, an inherent part of theological justice begins the discussion. The importance of moral reasoning for justice comes into conflict with Rawls’s idea that there should be no thick theory of the good influencing justice. Human dignity is an important facet of justice. The inalienable dignity owed to every human being, created in the image of God, is an essential part of theology and can enrich secular theories of justice. Justice necessitates community. People learn how to behave in a way which is just, moral and ethical from their associations in communities. The church community can provide an important place where dialogue and learning can take place. The boundaries of justice are ever-increasing. Globalisation presents challenges to where and how justice is implemented and we become increasingly aware of how our actions affect other people. The responsibility of the struggle for justice is everincreasing. The eschatological hope and the specific way of life which can be offered by the church complete the Christian notion of justice. / AFRIKAANSE OPSOMMING: Hierdie tesis is ’n kritiese studie van die werk van die politieke filosoof John Rawls en die teoloog Reinhold Niebuhr. Hierdie denkers se werk word met teologiese nadenke in gesprek gebring om sodoende ’n Christelike idee van geregtigheid te vorm wat meer as billikheid wil wees, en wat terselfdertyd die onmoontlikheid van perfekte liefde in dié wêreld erken. Rawls se twee beginsels van geregtigheid vorm die basis van die argument, deurdat vryheid voor gelykheid geplaas word en met die enigste toelaatbare ongelykhede dié wat tot die swakstes se voordeel is. Hy maak nie gebruik van godsdienstige of morele arugmente om geregtigheid te begrond of vul nie – enige begrip van die goeie moet in ooreenstemming met die regte wees en slegs ’n dun teorie van die goeie is nodig om mense in die regte rigting te lei. Hy aanvaar in sy latere werk dat die meeste mense tog deur morele denke of godsdiens gelei sal word. Niebuhr glo dat ’n profetiese godsdiens ’n diepe erns met die geskiedenis met ’n transendente norm kombineer. Hoop, geloof en liefde vorm die grondslag van ’n oproep tot ’n voortdurende stryd om geregtigheid en gelykheid. Die beperkinge waarbinne geregtigheid gesoek word, word voortdurend uitgebrei soos globale samewerking en afhanklikheid verhoog. Volmaakte geregtigheid sou ’n toestand van solidariteit met geen konflik van belange wees. Omdat mense 'n kombinasie van vitaliteit en rede is, kan die sosiale kohesie van die lewe nooit op suiwer rasionaliteit gebaseer word nie. Óns waarheid is nooit dié waarheid nie en ons is altyd subjektief en bevooroordeeld. Daar kan geen universele rasionele standaarde van geregtigheid of neutraliteit in die sosiale stryd wees nie. Liefde is die primêre wet van die natuur en ’n fundamentele vereiste vir sosiale bestaan. Ons word geroep tot betrokkenheid in die samelewing op grond van die regverdigmaking deur geloof. Gelykheid as die toppunt van geregtigheid verwys na liefde as die finale norm van geregtigheid, want gelyke geregtigheid is die verwesenliking van die gemeenskap onder die voorwaardes van die sonde. Geregtigheid as onvolmaakte liefde het gelykheid wat toenemend inklusief is en voortdurend ruimte skep waar mense in harmonie kan lewe ten doel. In die laaste hoofstuk van hierdie studie word Rawls en Niebuhr in kritiese gesprek met ander teoloë gebring. Die bespreking begin met die Christelike voorrang vir die armes, ’n basiese element van teologiese geregtigheid. Die belang van morele redenering vir geregtigheid kom in konflik met Rawls se idee dat enige dik teorie van die goeie geregtigheid nie behoort te beïnvloed nie. Menswaardigheid is 'n belangrike faset van geregtigheid. Elke mens – as beeld van God – se onvervreembare waardigheid, vorm ’n noodsaaklike deel van die teologie en kan sekulêre teorieë van geregtigheid verryk. Geregtigheid vereis gemeenskap. Mense kan in gemeenskappe leer hoe om op te tree op 'n manier wat regverdig, moreel en eties is. Die kerk as gemeenskap kan 'n belangrike plek wees waar dialoog en opvoeding kan plaasvind. Die omvang van geregtigheid neem steeds toe. Globalisering bied uitdagings oor waar en hoe geregtigheid geïmplementeer behoort te word en ons raak meer bewus van hoe ons aksies ander mense beïnvloed. Die verantwoordelikheid vir die stryd om geregtigheid neem ook steeds toe. Die eskatologiese hoop en die manier van lewe wat die kerk kan aanbied voltooi die Christelike idee van geregtigheid.

The objectives of this thesis are: (1) to investigate the antecedents and consequences of fairness of performance evaluation processes (procedural fairness) in the context of performance measurement, evaluation, and reward systems; and (2) to investigate the behavioural effects of reliance on multiple performance measures (RMPM) in evaluating subordinates' performance. In relation to the first objective, it examines whether managers' perceptions of procedural fairness are influenced by the form (financial or nonfinancial) of performance measures used to evaluate performance, and by goal-related variables such as participation in setting performance targets, the goal-attainment-reward link, and the specificity of goals to be achieved by managers. With regard to the consequences of procedural fairness, it examines the effects of procedural fairness on job satisfaction, performance, organisational commitment, and goal commitment, and also examines whether any such associations are direct or indirect. In relation to the second objective, it examines whether RMPM affects managerial performance or whether the effect is contingent on goal difficulty and goal specificity. To address these objectives, this thesis draws on organisational justice theory and goal theory and employs both quantitative and qualitative approaches. Quantitative data are collected using a questionnaire survey sent to managers in four organisations and qualitative data are gathered by means of interviews and focus group discussions within the organisations. The results indicate that procedural fairness is affected by participation in setting performance targets, the goal-attainment-reward link, and the specificity of goals to be achieved by managers, but not by the type of performance measure used to evaluate performance. With regard to the consequences of procedural fairness, the results indicate that: (1) the effects of procedural fairness on job satisfaction and performance are indirect and fully mediated by distributive fairness, trust, and organisational commitment; (2) the effect of procedural fairness on organisational commitment is partially mediated by distributive fairness and trust; and (3) the effect of procedural fairness on goal commitment is partially mediated by trust. Finally, the results indicate that the effect of RMPM on performance is contingent on goal specificity, but not on goal difficulty.

published_or_final_version / Business / Doctoral / Doctor of Philosophy

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Multi-hop wireless networks based on 802. 11 are being used more widely as an alternative technology for last-mile broadband Internet access. Their benefits include ease of deployment and lower cost. Such networks are not without problems. Current research on such networks aims at a number of challenges, including overcoming capacity limitation and poor fairness. <br /><br /> The focus of our research is for achieving fairness in multi-channel multi-hop wireless networks. First, we review the literature for different methods for representing link-contention areas, and the existing single-channel fairness computational model. Second, we generalize the fairness constraints applied to each link-contention area, defined in the existing single-channel fairness reference model, to multi-channel models. Third, by adopting the concepts of link-usage matrix and medium-usage matrix to represent network topology and flow status, and using Collision Domain theory and Clique Graph theory to represent link-contention area, we develop a computational model to compute optimal MAC-layer bandwidth allocated to each flow in a multi-channel multi-hop WMN. We simulate various network configurations to evaluate the performance of the fairness algorithm based on the above computational model in different scenarios. We have found that in the multi-channel environment, our extension to the Collision Domain model generally provides a more accurate estimation of network capacity. Based on this model, we have extended the source-rate-limiting mechanism, which limits the flow rate to its fair share computed by the computational model. Experimental results that validate these findings are presented in this thesis.

Ad hoc networks represent the current de-facto alternative for infrastructure-less environments, due to their self-configuring and resilience characteristics. Ad hoc networks flexibility benefits, such as unrestrained computing, lack of centralisation, and ease of deployment at low costs, are tightly bound with relevant deficiencies such as limited resources and management difficulty. Ad hoc networks witnessed high attention from the research community due to the numerous challenges faced when deploying such a technology in real scenarios. Starting with the nature of the wireless environment, which raises significant transmission issues when compared with the wired counterpart, ad hoc networks require a different approach when addressing the data link problems. Further, the high packet loss due to wireless contention, independent of network congestion, requires a different approach when considering quality of service degradation and unfair channel resources distribution among competing flows. Although these issues have already been considered to some extent by researchers, there is still room to improve quality of service by reducing the effect of packet loss and fairly distributing the medium access among competing nodes. The aim of this thesis is to propose a set of mechanisms to alleviate the effect of packet loss and to improve fairness in ad hoc networks. A transport layer algorithm has been proposed to overcome the effects of hidden node collisions and to reduce the impact of wireless link contention by estimating the four hop delay and pacing packet transmissions accordingly. Furthermore, certain topologies have been identified, in which the standard IEEE 802.11 faces degradation in channel utilisation and unfair bandwidth allocation. Three link layer mechanisms have been proposed to tackle the challenges the IEEE 802.11 faces in the identified scenarios to impose fairness in ad hoc networks through fairly distributing channel resources between competing nodes. These mechanisms are based on monitoring the collision rate and penalising the greedy nodes where no competing nodes can be detected but interference exists, monitoring traffic at source nodes to police access to the channel where only source nodes are within transmission range of each other, and using MAC layer acknowledgements to flag unfair bandwidth allocation in topologies where only the receivers are within transmission range of each other. The proposed mechanisms have been integrated into a framework designed to adapt and to dynamically select which mechanism to adopt, depending on the network topology. It is important to note that the proposed mechanisms and framework are not alternatives to the standard MAC protocol but are an enhancement and are triggered by the failure of the IEEE 802.11 protocol to distribute the channel resources fairly. All the proposed mechanisms have been validated through simulations and the results obtained from the experiments show that the proposed schemes fairly distribute channel resources fairly and outperform the performance of the IEEE 802.11 protocol in terms of channel utilisation as well as fairness.