Facial recognition technology has become a ubiquitous tool in security and personal identification. However, the rise of this technology has been accompanied by concerns over inherent biases, particularly regarding ethnic and gender. This thesis examines the extent of these biases by focusing on the influence of dataset imbalances in facial recognition algorithms. We employ a structured methodological approach that integrates AI-generated images to enhance dataset diversity, with the intent to balance representation across ethnics and genders. Using the ResNet and Vgg model, we conducted a series of controlled experiments that compare the performance impacts of balanced versus imbalanced datasets. Our analysis includes the use of confusion matrices and accuracy, precision, recall and F1-score metrics to critically assess the model’s performance. The results demonstrate how tailored augmentation of training datasets can mitigate bias, leading to more equitable outcomes in facial recognition technology. We present our findings with the aim of contributing to the ongoing dialogue regarding AI fairness and propose a framework for future research in the field.

Student selection is particularly challenging in South Africa. Heterogeneous educational backgrounds require that it is necessary to assess prospective students' potential rather than their current abilities that crystallised from inadequate school education. Dynamic assessment assesses learning potential versus traditional psychometric measures, which are static measures of cognitive ability, measuring what a person has already learned. The aim was to determine the predictive validity of a selection battery. The following predictors were included in the study; matric results, Potential Index Battery, LPCAT, bridging course status and gender. The results confirmed that static measures of intelligence and matric results showed lower predictive validity than learning potential tests. The learning potential measure appeared to be a more valid predictor of academic performance and is suitable to include in a selection battery. Gender and bridging course factors did not reflect significant differences in academic performance. There were indications that students perform better in successive years of study, once they have adjusted to tertiary education. / Industrial and Organisational Psychology / M. Comm. (Industrial and Organisational Psychology)

Developing an adjudicative institutional framework for effective social security provisioning in South Africa entails the establishment of a system that gives effect to the rights (of access) to social security and to justice. These rights are protected in the Constitution and in various international law instruments. In the Constitution, the Bill of Rights guarantees everyone the right to have access to social security, including appropriate social assistance for persons who are unable to support themselves and their dependants. It further requires the State to take reasonable legislative and other measures, within its available resources, to achieve the progressive realisation of the right to access to social security. Since a dispute resolution (adjudication) framework is an integral part of any comprehensive social security system, it is included in the constitutional obligation of the State. The establishment of a social security adjudication system is an intersection of the right of access to social security and the right of access to justice. The Constitution states that everyone has the right to have any dispute that can be resolved by the application of law decided in a fair public hearing before a court or, where appropriate, another independent and impartial tribunal or forum. In addition, other rights protected in the Constitution have a bearing on the realisation of the rights of access to social security and to justice. There is a close correlation between all the rights in the Bill of Rights, as they are interrelated, interdependent and mutually supporting. They must all be read together in the setting of the Constitution as a whole and their interconnectedness must be taken into account in interpreting rights; and in determining whether the State has met its obligations in terms of any one of them. These rights, which include the right to equality (section 9), the right to human dignity (section 10) and the right to just administrative action (section 33) must thus be considered in establishing a social security adjudication system. Also to be considered are other constitutional prerequisites for the establishment of a social security adjudication system, such as the limitation and enforcement of rights (sections 36 and 38 respectively); principles relating to courts and the administration of justice (Chapter 8) and basic values and principles governing public administration (Chapter 10). In establishing a social security adjudication system in South Africa, international law standards and developments in comparative systems must also be taken into account. The Constitution adopts an international law- and comparative law-friendly approach. It states that when interpreting fundamental rights, international law must be considered while foreign law may be considered (section 39). This thesis aims to develop an adjudicative and institutional framework for effective social security provisioning in South Africa that realises the rights of access to social security and to justice in the South African social security system. This is achieved by exploring the concept of access to justice, and its application in the social security adjudication system. The current social security adjudication system is evaluated against the concept of access to justice applicable in international and regional law instruments, comparable South African (non-social security) systems and comparative international jurisdictions. Principles and standards on the establishment of a social security adjudication system are distilled; and a reformed system for South Africa is proposed. / Mercantile Law / LL.D.

This item contains the agenda, minutes, and attachments for the Faculty Senate meeting on this date. There may be additional materials from the meeting available at the Faculty Center.

本論文之主要論旨，在於探討公平正義是否可能在裁判之過程中獲得實現。筆者主要透過德沃金的法理論以及平等理論作為討論的出發點。筆者首先對於德沃金的理論進行相關的分析與討論。德沃金的法理論主要可區分為四個部分，包括：語義階段，法理階段，原理階段，以及裁判階段。在語義階段，德沃金指出，法律的概念，必須要作為一個詮釋性概念；在法理階段，德沃金將法律的概念當成一種政治價值的概念。德沃金認為，法律的概念所表彰的政治價值，便是「合法性價值」，亦即「法治」。進一步，德沃金指出，對於「合法性價值」與「法律的概念」的最佳理解，便是「整全性」。筆者認為，「整全性」是一個連接德沃金的「法理論」以及「平等理論」的關鍵概念。在《法律帝國》一書當中，德沃金主張：裁判的整全性，要求法官適用由公平與正義原則所推導出來的法律。這樣的主張，將我們帶向德沃金的平等理論。 德沃金的平等理論可以區分為兩個層面，一為討論關於分配正義的資源平等理論，另一為關乎政治權力分配的政治平等理論。這兩個概念，提供了司法裁判實踐公平正義的可能性。資源平等理論提供了相關的判準，可以使法院在裁判具體個案時得以援引，以判斷公民所擁有的具體權利，以及政府是否違反了在平等關懷下所需踐行的平等保護原則，而導致侵害人民的權利。同時，政治平等理論則為民主制度下的司法審查，提供其理論基礎。 最後，德沃金指出，關於裁判如何適用法律於具體個案的裁判過程，其與上述三階段有密切的關聯性。德沃金認為，在此一階段中，他與法實證主義者最大的不同，便是在於對於法官的裁量權的理解。德沃金認為，在其法理論體系當中，法官對裁量權的行使，是一種法律義務，而非如法實證主義者所稱，是一種道德責任。 不可避免的，對於德沃金的理論，存在有許多的反對意見。在此筆者援引了Joseph Raz以及Samuel Schaffler的論文，對德沃金的理論進行檢試。Raz指出，德沃金的理論本身，與其所主張的融貫並未有直接的關係，同時，德沃金的理論，忽略了權威在現代國家中所扮演的角色。Schaffler則指出，德沃金過份的強調經濟平等，因而致政治或社會平等遭到忽視。此外，Schaffler認為，德沃金的資源平等理論裡，欠缺對於境況與志向的區分標準。最後，Schaffler則是提到，德沃金的資源平等理論，隱藏著存在階級社會的可能性。 的確，Joseph Raz以及Samuel Schaffler的論文提供了反思性的觀點，不過，筆者認為，他們所提出的問題，無法成功的全然拒絕德沃金的理論。筆者認為，德沃金的法理論，成功的融合了「法治」以及「正義」與「公平」，因此，其理論也確實為司法裁判實踐公平正義的理念，提供了可能了路徑。 關鍵字：公平、正義、語義階段，法理階段，原理階段，裁判階段、法理論、平等、整全性、融貫、平等關懷 / The main issue of my thesis focuses on whether realization of the ideal of justice and fairness in adjudication is possible. I discuss this main issue by means of Dworkin’s legal theory and his theory of equality. First of all, I start my discussion with analysis of Dworkin’s legal theory, which includes four stages: the semantic stage, the jurisprudential stage, the doctrinal stage, and the adjudicative stage. In semantic stage, Dworkin points out that the concept of law should be interpretive concept. In jurisprudential stage, he deems the concept of law as a concept of political values, and what the value presented by concept of law is the value of legality. Furthermore, he considers the best concept of the value of the legality, so as the best conception of law, is integrity. I believe this is the key concept which connects Dworkin’s legal theory with theory of equality. In Law’s Empire, Dworkin said that integrity in adjudication asks judges apply the laws which come from the principle of justice and fairness. This leads us to Dworkin’s theory of equality. Dworkin presents his theory of Equality with two dimensions. One is equality of resources, which could be narrowly seen as a theory about distributive justice. The other is political equality concerning the distribution of political power. These two dimensions of his theory of equality offer the possibility of realizing the justice and fairness in adjudication. The theory of equality of resources offers the guidelines for courts to follow when deciding if citizens have some sort of concrete rights, and if government violates the equal protection of citizen’s rights that demanded by the ideal of equal concern. According to political equality, it offers the basis of judicial review in democracy. Finally, Dworkin points out that how judges apply laws to concrete case is something related to those three stages as mentioned above. Dworkin distinguishes himself from the legal positivists, such as Hans Kelsen and H.L.A. Hart. The different between Dworkin and legal positivists is discretion power of judges. In his theory, it is judge’s legal obligation rather than moral responsibility as positivists regard. Inevitably, there are some critics to Dworkin’s theory of equality. Here I cited the research of Joseph Raz and Samuel Schaffler to exam Dworkin’s theory. Their articles offer reflective points of view to me. Joseph Raz criticizes Dworkin’s theory as something irrelative to the coherence that Dworkin himself requests. He further criticizes that Dworkin’s theory of adjudication ignores the role of authority in modern state. Samuel Scheffler criticizes that Dworkin’s theory of equality ignores the importance of political and social equality. Besides, how to distinguish circumstance and ambition is not clear enough in Dworkin’s theory. Furthermore, Scheffler considers that Dworkin’s theory of equality may allow a heirachy administration exists. Although they point out some defects, I do not think they did fulfill significant challenges to Dworkin’s theory. After all, I consider that Dworkin’s legal theories build up a perfect framework for realizing the value of legality, which can also be referred as the rule of law. Most importantly, his legal theories are coherent the other moral values and convictions of ethics. I think Dworkin’s theories of law and equality may offer the best possibility to realize the ideal of justice and fairness in adjudication. Key Words: justice, fairness, the semantic stage, the jurisprudential stage, the doctrinal stage, the adjudicative stage, integrity, coherence, legal theory, equality, equal concern

Si le respect du droit à un procès équitable devrait occuper une place éminente au sein de toute société démocratique, cette exigence revêt un caractère axiomatique au sein d'une juridiction tournée vers la lutte contre l'impunité et la protection des droits de l'homme, telle que la Cour pénale internationale. Le peu de jugements rendus depuis plus de dix ans par la Cour permanente pourrait laisser penser qu'une telle étude est encore prématurée. Cette analyse met au contraire en exergue la densité de son activité et la singularité de ses procédures. Sacralisé par la Cour européenne des droits de l'homme, le droit à un procès équitable se décline en règles qui régissent non seulement les relations entre les parties mais aussi les rapports des individus avec la juridiction. Si la notion de droit à un procès équitable est familière des juristes, son interprétation pose un certain nombre de difficultés nouvelles. L'hybridité structurelle et normative de la Cour pénale internationale influencera nécessairement la réception que celle-ci réservera au principe, mais également l'interprétation unique qu'il conviendra de donner à ce droit fondamental. Prenant acte du caractère novateur de cette juridiction, cette thèse n'omettra pas d'envisager le droit à un procès équitable sous le prisme singulier de la victime, nouveau visage du procès. Souvent exclue du débat judiciaire relatif à l'équité des procédures, cette analyse s'attèle à replacer cet acteur au coeur des préoccupations régissant la conduite équitable du procès. / While the right to a fair trial should be at the heart of any democratic society, this requirement has an axiomatic significance in a court dedicated to the fight against impunity and the protection of human rights, such as the International Criminal Court. In view of the few judgments rendered in over ten years of this permanent Court's existence, this study might seem somewhat premature.Rather, this analysis purports to shed light on the diverse nature of the Court's activities and the unique character of its procedures. Enshrined by the European Court of Human Rights, the right to a fair trial is expressed in the form of regulations that govern not only the relationships between the parties, but also the interaction of individuals with the Court. The concept of the right to a fair trial may be familiar to legal experts trained in different legal traditions. Still its interpretation is fraught with challenges that are new and specific to this permanent Court. The structural and normative hybridity of the ICC will inevitably influence not only the treatment of this concept, but also the unique interpretation that this fundamental right deserves. Against the backdrop of the innovative nature of this Court, it would be remiss of the author of this thesis not to consider the right to a fair trial through the unique prism of the victim, the new face in the trial. Often excluded from the judicial debate on the fairness of the proceedings, this analysis will nevertheless endeavour to place this stakeholder back in the heart of the concerns over the conduct of a fair trial.

Made available in DSpace on 2016-04-26T20:20:13Z (GMT). No. of bitstreams: 1 Fernanda Vasconcelos Fontes Piccina.pdf: 983394 bytes, checksum: 27a2865b16640cd8382e1db5726924e4 (MD5) Previous issue date: 2011-06-13 / The present work aims the study of the Due Process of Law and its implications in administrative disciplinary proceedings. It starts with the background of Due Process in the Brazilian legal and a brief historical description of the principle and its analysis, based on the phenomena of constitutionalization of the law. The study of administrative disciplinary proceedings is made, initially from the general approach of this process at the federal level, from the perspective of Law 8112/90, with the analysis of each of its phases, moving after, the study of principles that give concreteness to the Due Process of Law as well as the consequences of its impact on the process under study. The work contains, therefore, the study in furtherance of the principles of due process of law, namely: contradictory and full defense, natural judge, reasonableness and proportionality and, finally, a reasonable duration of proceedings. In items where the above principles are studied, sought to conceptualize them and examine its foundations, scope and direction in the processes of disciplinary sanctions in order to verify their impact in specific cases, as well as the understanding of the Superior Courts on the matter / O presente trabalho tem por objeto o estudo do devido processo legal e suas implicações no processo administrativo disciplinar. Parte-se da contextualização do Devido Processo Legal no ordenamento jurídico brasileiro e de uma breve descrição histórica do princípio e da sua análise, tomando por base o fenômeno da constitucionalização do Direito. O estudo do processo administrativo disciplinar é feito, inicialmente, a partir de abordagem geral desse processo na esfera federal, sob a ótica da Lei 8112/90, com a análise de cada uma de suas fases, passando-se, após, ao estudo dos princípios que conferem concretude ao Devido Processo Legal, bem como as consequências da sua incidência no processo em estudo. O trabalho compreende, assim, o estudo dos princípios concretizadores do Devido Processo Legal, quais sejam: contraditório e ampla defesa, juiz natural, razoabilidade e proporcionalidade e, por fim, a razoável duração do processo. Nos itens em que os mencionados princípios são estudados, buscou-se conceituá-los e examinar seus fundamentos, sentido e alcance nos processos de aplicação de sanções disciplinares, de modo a constatar a sua incidência nos casos concretos, bem como o entendimento dos Tribunais Superiores sobre a matéria

本研究之目的在了解使用同儕評量為考核方式時，可能影響團體成員公平知覺等心理反應的因素。研究中以96名大學女生為實驗對象，採2x2x2實驗設計，探討“同儕評量與自評之差異”、“團體成員相對親疏關係”及“決策控制力（自評對獎金分配之影響力）”等三個因素對團體成員公平知覺之影響，並了解內外控傾向在此影響機制中扮演的角色。研究結果顯示，當團體使用同儕評量之考核方法時，“同儕評量與自評之差異”對個體的公平知覺、結果滿意、團體吸引力、再次合作意願均有非常顯著的影響。顯示個體相當關心自我評量與同儕評量之差異，當同儕評量比自評低時，個人在以上幾種心理反應都顯著的較弱。在“相對親疏關係”上，結果顯示個體進入團體中時，若感覺其他兩位成員間之親疏關係，比個體自己與其他任一人間為親密時，其公平知覺會較低。在“決策控制力”上，則發現其對公平知覺與再次合作意願有顯著影響，當自評對酬賞結果具有影響力（決策控制力高）時，個體的公平知覺會較高，也較願意再次與其他兩位成員合作。在“同儕評量與自評之差異”、“相對親疏關係”、“決策控制力”三者之交互作用方面，分析結果顯示均未達顯著。在內外控此變項上，除發現其對公平知覺有顯著影響，即愈外控者之公平知覺愈低外，另亦顯示內外控與“相對親疏關係”具有交互作用，但與“決策控制力”、“同儕評量與自評之差異”之交互作用並不顯著，表示內外控只在“相對親疏關係”對公平知覺之影響上有調節效果。本研究最後對未獲驗證之部份加以討論，並依實驗所得結果，提出可能之貢獻、限制、對未來研究的建議及工商實務上之應用。 / This study, employing 96 undergraduates and 2×2×2 experimental design, examined the effects of “discrepancies between peer rating and self rating”, “ relative relationship” and “decision control (the influence of self rating on reward) ” to group members’ perception of fairness. The role of locus of control was also explored. When using the peer rating, subjects who received relative lower peer rating showed weaker perception of fairness, less satisfied with outcome, less attracted to other two coworkers and lower recooperative willing. Subjects perceived fairer when the relative relationship is equal (the familiarity within group members is the same). With the high decision control, subjects’ perception of fairness and recooperative willing were higher. No interaction effect of these three independent variables was found. Locus of control had moderating effect on the relation between relative relationship and perception of fairness. Implications for management and future research are discussed.

Multiple-input, multiple-output (MIMO) techniques have been proposed to meet the needs for higher data rates and lower delays in future wireless communication systems. The downlink capacity of multiuser MIMO systems is achieved when the system transmits to several users simultaneously. Frequently, many more users request service than the transmitter can simultaneously support. Thus, the transmitter requires a scheduling algorithm for the users, which must balance the goals of increasing throughput, reducing multiuser interference, lowering delays, ensuring fairness and quality of service (QoS), etc. In this thesis, we investigate the application of genetic algorithms (GAs) to perform scheduling in multiuser MIMO systems. GAs are a fast, suboptimal, low-complexity method of solving optimization problems, such as the maximization of a scheduling metric, and can handle arbitrary functions and QoS constraints. We first examine a system that transmits using capacity-achieving dirty paper coding (DPC). Our proposed GA structure both selects users and determines their encoding order for DPC, which affects the rates they receive. Our GA can also schedule users independently on different carriers of a multi-carrier system. We demonstrate that the GA performance is close to that of an optimal exhaustive search, but at a greatly reduced complexity. We further show that the GA convergence time can be significantly reduced by tuning the values of its parameters. While DPC is capacity-achieving, it is also very complex. Thus, we also investigate GA scheduling with two linear precoding schemes, block diagonalization and successive zero-forcing. We compare the complexity and performance of the GA with "greedy" scheduling algorithms, and find the GA is more complex, but performs better at higher signal-to-noise ratios (SNRs) and smaller user pool sizes. Both algorithms are near-optimal, yet much less complex than an exhaustive search. We also propose hybrid greedy-genetic algorithms to gain benefits from both types of algorithms. Lastly, we propose an improved method of optimizing the transmit covariance matrices for successive zero-forcing. Our algorithm significantly improves upon the performance of the existing method at medium to high SNRs, and, unlike the existing method, can maximize a weighted sum rate, which is important for fairness and QoS considerations. / Communications

Τα κατανεμημένα δίκτυα κλίμακας Ίντερνετ και κυρίως τα δίκτυα ομοτίμων εταίρων, γνωστά και ως peer-to-peer (p2p), που αποτελούν το πιο αντιπροσωπευτικό παράδειγμά τους, προσελκύουν τα τελευταία χρόνια μεγάλο ενδιαφέρον από τους ερευνητές και τις επιχειρήσεις λόγω των ιδιόμορφων χαρακτηριστικών τους, όπως ο πλήρης αποκεντρωτικός χαρακτήρας, η αυτονομία των κόμβων, η ικανότητα κλιμάκωσης, κ.λπ. Αρχικά σχεδιασμένα να υποστηρίζουν εφαρμογές διαμοιρασμού αρχείων με βασική υπηρεσία την επεξεργασία απλών ερωτημάτων, σύντομα εξελίχτηκαν σε ένα καινούργιο μοντέλο κατανεμημένων συστημάτων, με μεγάλες και αυξανόμενες δυνατότητες για διαδικτυακές εφαρμογές, υποστηρίζοντας πολύπλοκες εφαρμογές διαμοιρασμού δομημένων και σημασιολογικά προσδιορισμένων δεδομένων. Η προσέγγισή μας στην περιοχή αυτή γίνεται προς δύο βασικές κατευθύνσεις: (α) την επεξεργασία πολύπλοκων ερωτημάτων και (β) την εκτίμηση των ανομοιομορφιών των διαφόρων κατανομών που συναντάμε στα δίκτυα αυτά (π.χ. φορτίου, προσφοράς ή κατανάλωσης ενός πόρου, τιμών των δεδομένων των κόμβων, κ.λπ.), που εκτός των άλλων αποτελεί ένα σημαντικό εργαλείο στην υποστήριξη πολύπλοκων ερωτημάτων. Συγκεκριμένα, ασχολούμαστε και επιλύουμε τρία βασικά ανοικτά προβλήματα. Το πρώτο ανοικτό πρόβλημα είναι η επεξεργασία ερωτημάτων εύρους τιμών σε ομότιμα συστήματα κατανεμημένου πίνακα κατακερματισμού, με ταυτόχρονη εξασφάλιση της εξισορρόπησης του φορτίου των κόμβων και της ανοχής σε σφάλματα. Προτείνουμε μια αρχιτεκτονική επικάλυψης, που ονομάζουμε Saturn, που εφαρμόζεται πάνω από ένα δίκτυο κατανεμημένου πίνακα κατακερματισμού. Η αρχιτεκτονική Saturn χρησιμοποιεί: (α) μια πρωτότυπη συνάρτηση κατακερματισμού που τοποθετεί διαδοχικές τιμές δεδομένων σε γειτονικούς κόμβους, για την αποδοτική επεξεργασία των ερωτημάτων εύρους τιμών και (β) την αντιγραφή, για την εξασφάλιση της εξισορρόπησης του φορτίου προσπελάσεων (κάθετη, καθοδηγούμενη από το φορτίο αντιγραφή) και της ανοχής σε σφάλματα (οριζόντια αντιγραφή). Μέσα από μια εκτεταμένη πειραματική αξιολόγηση του Saturn και σύγκριση με δύο βασικά δίκτυα κατανεμημένου πίνακα κατακερματισμού (Chord και OP-Chord) πιστοποιούμε την ανωτερότητα του Saturn να αντιμετωπίζει και τα τρία ζητήματα που θέσαμε, αλλά και την ικανότητά του να συντονίζει το βαθμό αντιγραφής ώστε να ανταλλάζει ανάμεσα στο κόστος αντιγραφής και στο βαθμό εξισορρόπησης του φορτίου. Το δεύτερο ανοικτό πρόβλημα που αντιμετωπίζουμε αφορά την έλλειψη κατάλληλων μετρικών που να εκφράζουν τις ανομοιομορφίες των διαφόρων κατανομών (όπως, για παράδειγμα, το βαθμό δικαιοσύνης μιας κατανομής φορτίου) σε κατανεμημένα δίκτυα κλίμακας Ίντερνετ και την μη αποτελεσματική ή δυναμική εκμετάλλευση μετρικών ανομοιομορφίας σε συνδυασμό με αλγορίθμους διόρθωσης (όπως ο αλγόριθμος εξισορρόπησης φορτίου). Το πρόβλημα είναι σημαντικό γιατί η εκτίμηση των κατανομών συντελεί στην ικανότητα κλιμάκωσης και στην επίδοση αυτών των δικτύων. Αρχικά, προτείνουμε τρεις μετρικές ανομοιομορφίας (το συντελεστή του Gini, τον δείκτη δικαιοσύνης και το συντελεστή διασποράς) μετά από μια αναλυτική αξιολόγηση μεταξύ γνωστών μετρικών εκτίμησης ανομοιομορφίας και στη συνέχεια, αναπτύσσουμε τεχνικές δειγματοληψίας (τρεις γνωστές τεχνικές και τρεις προτεινόμενες) για τη δυναμική εκτίμηση αυτών των μετρικών. Με εκτεταμένα πειράματα αξιολογούμε συγκριτικά τους προτεινόμενους αλγορίθμους εκτίμησης και τις τρεις μετρικές και επιδεικνύουμε πώς αυτές οι μετρικές και ειδικά, ο συντελεστής του Gini, μπορούν να χρησιμοποιηθούν εύκολα και δυναμικά από υψηλότερου επιπέδου αλγορίθμους, οι οποίοι μπορούν τώρα να ξέρουν πότε να επέμβουν για να διορθώσουν τις άδικες κατανομές. Το τρίτο και τελευταίο ανοικτό πρόβλημα αφορά την εκτίμηση του μεγέθους αυτοσύνδεσης μιας σχέσης όπου οι πλειάδες της είναι κατανεμημένες σε κόμβους δεδομένων που αποτελούν ένα ομότιμο δίκτυο επικάλυψης. Το μέγεθος αυτοσύνδεσης έχει χρησιμοποιηθεί εκτεταμένα σε συγκεντρωτικές βάσεις δεδομένων για τη βελτιστοποίηση ερωτημάτων και υποστηρίζουμε ότι μπορεί να χρησιμοποιηθεί και σε ένα πλήθος άλλων εφαρμογών, ειδικά στα ομότιμα δίκτυα (π.χ. συσταδοποίηση του Ιστού, αναζήτηση στον Ιστό, κ.λπ.). Η συνεισφορά μας περιλαμβάνει, αρχικά, τις προσαρμογές πέντε γνωστών συγκεντρωτικών τεχνικών εκτίμησης του μεγέθους αυτοσύνδεσης (συγκεκριμένα, σειριακή, ετεροδειγματοληπτική, προσαρμοστική και διεστιακή δειγματοληψία και δειγματοληψία με μέτρηση δείγματος) στο περιβάλλον ομοτίμων εταίρων και η ανάπτυξη μια πρωτότυπης τεχνικής εκτίμησης του μεγέθους αυτοσύνδεσης, βασισμένη στο συντελεστή του Gini. Με μαθηματική ανάλυση δείχνουμε ότι οι εκτιμήσεις του συντελεστή του Gini μπορούν να οδηγήσουν σε εκτιμήσεις των υποκείμενων κατανομών δεδομένων, όταν αυτά ακολουθούν το νόμο της δύναμης ή το νόμο του Zipf και αυτές, με τη σειρά τους, σε εκτιμήσεις του μεγέθους αυτοσύνδεσης των σχέσεων των δεδομένων. Μετά από αναλυτική πειραματική μελέτη και σύγκριση όλων των παραπάνω τεχνικών αποδεικνύουμε ότι η καινούργια τεχνική που προτείνουμε είναι πολύ αποτελεσματική ως προς την ακρίβεια, την πιστότητα και την απόδοση έναντι των άλλων πέντε μεθόδων. / The distributed, Internet-scale networks, and mainly, the peer-to-peer networks (p2p), that constitute their most representative example, recently attract a great interest from the researchers and the industry, due to their outstanding properties, such as full decentralization, autonomy of nodes, scalability, etc. Initially designed to support file sharing applications with simple lookup operations, they soon developed in a new model of distributed systems, with many and increasing possibilities for Internet applications, supporting complex applications of structured and semantically rich data. Our research to the area has two basic points of view: (a) complex query processing and (b) estimation of skewness in various distributions existing in these networks (e.g. load distribution, distribution of offer, or consumption of resources, data value distributions, etc), which, among others, it is an important tool to complex query processing support. Specifically, we deal with and solve three basic open problems. The first open problem is range query processing in p2p systems based on distributed hash tables (DHT), with simultaneous guarantees of access load balancing and fault tolerance. We propose an overlay DHT architecture, coined Saturn. Saturn uses a novel order-preserving hash function that places consecutive data values in successive nodes to provide efficient range query processing, and replication to guarantee access load balancing (vertical, load-driven replication) and fault tolerance (horizontal replication). With extensive experimentation, we evaluate and compare Saturn with two basic DHT networks (Chord and OP - Chord), and certify its superiority to cope with the three above requirements, but also its ability to tune the degree of replication to trade off replication costs for access load balancing. The second open problem that we face concerns the lack of appropriate metrics to express the degree of skewness of various distributions (for example, the fairness degree of load balancing) in p2p networks, and the inefficient and offline-only exploitation of metrics of skewness, which does not enable any cooperation with corrective algorithms (for example, load balancing algorithms). The problem is important because estimation of distribution fairness contributes to system scalability and efficiency. First, after a comprehensive study and evaluation of popular metrics of skewness, we propose three of them (the coefficient of Gini, the fairness index, and the coefficient of variation), and, then, we develop sampling techniques (three already known techniques, and three novel ones) to dynamically estimate these metrics. With extensive experimentation, which comparatively evaluates both the various proposed estimation algorithms and the three metrics we propose, we show how these three metrics, and especially, the coefficient of Gini, can be easily utilized online by higher-level algorithms, which can now know when to best intervene to correct unfairness. The third and last open problem concerns self-join size estimation of a relation whose tuples are distributed over data nodes which comprise an overlay network. Self-join size has been extensively used in centralized databases for query optimization purposes, and we support that it can also be used in various other applications, specifically in p2p networks (e.g. web clustering, web searching, etc). Our contribution first includes the adaptations of five well-known self-join size estimation, centralized techniques (specifically, sequential sampling, cross-sampling, adaptive and bifocal sampling, and sample-count) to the p2p environment and a novel estimation technique which is based on the Gini coefficient. With mathematical analysis we show that, the estimates of the Gini coefficient can lead to estimates of the degree of skewness of the underlying data distribution, when these follow the power, or Zipf’s law, and these estimates can lead to self-join size estimates of those data relations. With extensive experimental study and comparison of all above techniques, we prove that the proposed technique is very efficient in terms of accuracy, precision, and cost of estimation against the other five methods.