Esta dissertação possui como tema central a investigação da tese de Martin Heidegger a respeito do caráter derivado da verdade proposicional com relação ao que é por ele concebido como o fenômeno originário da verdade. A interrogação sobre um horizonte mais originário da noção de verdade advém da convicção de Heidegger com respeito à negligência dos autores da tradição filosófica quanto à necessidade de uma fundamentação ontológica para a verdade proposicional. A raiz metafísica da verdade proposicional se encontraria no pressuposto aristotélico da substância (ou)si/a) como categoria fundamental do ser dos entes em geral. Heidegger, portanto, procurará desconstruir a noção de uma realidade constante e auto-subsistente como o fundamento ontológico da concepção hegemônica de verdade. A substancialidade do ser, até então, uma evidência inquestionável, passa agora a ser articulada pelo ser humano social e historicamente situado. Isso quer dizer que, de alguma forma, a concepção do ser como substância, ou presença constante, precisa ter sido estabelecida pelo ser humano e incorporada na história da filosofia de modo a se tornar a fundamentação metafísica da verdade. Todavia, Heidegger adverte que o estabelecimento da ontologia da substancialidade não é o resultado de uma simples escolha teórica humana. Ao contrário, essa fundamentação teórica estaria condicionada pelo próprio modo de ser do humano enquanto existente no mundo. / This dissertation holds as a central theme the investigation of Martin Heideggers thesis with respect to the derivative character of propositional truth in relation to what is considered by him as the originary phenomenon of truth. The interrogation about a more originary horizon of the notion of truth arises from Heideggers certitude in respect to the negligence of the authors of philosophical tradition towards the necessity of an ontological grounding to propositional truth. The metaphysical roots of propositional truth would be in the Aristotelian presumption of substance (ou)si/a) as fundamental category of the being of entities in general. Therefore, Heidegger will try to deconstruct the notion of a constant and self-subsistent reality as an ontological ground to the hegemonic conception of truth. The substantiality of being, till then, unquestionable evidence, is now articulated by the historically situated human being. It means that, somehow, the conception of being as substance, or constant presence, should have been established by human beings and incorporated in the history of philosophy in such a way that it became a metaphysical grounding of truth. Nevertheless, Heidegger warns that the establishing of the ontology of substantiality is not the result of a simple theoretical human choice. On the contrary, this theoretical grounding would be conditioned by the very mode of being of humans as existents in the world.

Esta dissertação possui como tema central a investigação da tese de Martin Heidegger a respeito do caráter derivado da verdade proposicional com relação ao que é por ele concebido como o fenômeno originário da verdade. A interrogação sobre um horizonte mais originário da noção de verdade advém da convicção de Heidegger com respeito à negligência dos autores da tradição filosófica quanto à necessidade de uma fundamentação ontológica para a verdade proposicional. A raiz metafísica da verdade proposicional se encontraria no pressuposto aristotélico da substância (ou)si/a) como categoria fundamental do ser dos entes em geral. Heidegger, portanto, procurará desconstruir a noção de uma realidade constante e auto-subsistente como o fundamento ontológico da concepção hegemônica de verdade. A substancialidade do ser, até então, uma evidência inquestionável, passa agora a ser articulada pelo ser humano social e historicamente situado. Isso quer dizer que, de alguma forma, a concepção do ser como substância, ou presença constante, precisa ter sido estabelecida pelo ser humano e incorporada na história da filosofia de modo a se tornar a fundamentação metafísica da verdade. Todavia, Heidegger adverte que o estabelecimento da ontologia da substancialidade não é o resultado de uma simples escolha teórica humana. Ao contrário, essa fundamentação teórica estaria condicionada pelo próprio modo de ser do humano enquanto existente no mundo. / This dissertation holds as a central theme the investigation of Martin Heideggers thesis with respect to the derivative character of propositional truth in relation to what is considered by him as the originary phenomenon of truth. The interrogation about a more originary horizon of the notion of truth arises from Heideggers certitude in respect to the negligence of the authors of philosophical tradition towards the necessity of an ontological grounding to propositional truth. The metaphysical roots of propositional truth would be in the Aristotelian presumption of substance (ou)si/a) as fundamental category of the being of entities in general. Therefore, Heidegger will try to deconstruct the notion of a constant and self-subsistent reality as an ontological ground to the hegemonic conception of truth. The substantiality of being, till then, unquestionable evidence, is now articulated by the historically situated human being. It means that, somehow, the conception of being as substance, or constant presence, should have been established by human beings and incorporated in the history of philosophy in such a way that it became a metaphysical grounding of truth. Nevertheless, Heidegger warns that the establishing of the ontology of substantiality is not the result of a simple theoretical human choice. On the contrary, this theoretical grounding would be conditioned by the very mode of being of humans as existents in the world.

Orientador: Orly Zucatto Mantovani de Assis / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Educação / Made available in DSpace on 2018-08-13T20:23:08Z (GMT). No. of bitstreams: 1 Carina_SandraCristina_D.pdf: 883383 bytes, checksum: 03d3d88c1e105e3e3b78767b3dab991e (MD5) Previous issue date: 2009 / Resumo: O cotidiano escolar é permeado por inúmeros conflitos interpessoais entre crianças e adolescentes. São situações muitas vezes julgadas como negativas pelos educadores, como algo a ser evitado. Não raro, os educadores distanciam-se de entender que suas formas de intervenção são geradoras de comportamentos submissos por parte de seus alunos. Tais comportamentos são oriundos de um ambiente em que o professor normalmente utiliza formas autoritárias para resolver os problemas que enfrenta no cotidiano escolar, colocando, muitas vezes, seus alunos em situações de humilhação, exposição, ou pura obediência a uma autoridade, sem que esses sejam convidados a pensar nas soluções que levem em conta as necessidades dos envolvidos, ou seja, em estilos assertivos de resolução de conflitos. Diante de tal justificativa, a presente pesquisa buscou investigar quais formas de resolução de conflito são comumente utilizadas pelos adolescentes, ainda que a partir de dilemas hipotéticos, e confrontá-las às formas que os professores apontaram como as que esses mesmos adolescentes utilizavam quando envolvidos em situações de conflitos. A amostra foi constituída por um total de trinta e nove participantes, préadolescentes entre onze e treze anos, estudantes do sexto ano de uma escola pública da região de Campinas, interior de São Paulo, e por cinco professores desses mesmos adolescentes. O instrumento utilizado consistiu numa entrevista semi-estruturada com professores e um instrumento criado por Robert Deluty e adaptado por Maria Isabel Leme que avalia simultânea e comparativamente três tipos de tendências de resolução de conflitos interpessoais - agressivo, assertivo e submisso - nas respostas dos pré-adolescentes a conflitos interpessoais hipotéticos cujos conteúdos sejam de provocações, perdas, frustrações etc. Os resultados obtidos nos permitem comprovar nossa hipótese de que a forma pela qual os adolescentes nas situações hipotéticas resolvem seus conflitos não coincide às formas apontadas previamente pelos professores das tendências de resolução de conflitos utilizadas por esses mesmos adolescentes quando envolvidos em situação de conflito no cotidiano escolar. Esses adolescentes estão mais propensos a estilos submissos de resolução de conflito do que a formas assertivas ou agressivas. / Abstract: The daily school life is permeated by a lot of interpersonal conflicts among children and adolescents. These situations are often judged as negative by educators, like something to be avoided. Sometimes educators don't make an effort to understand that their forms of intervention are generating submissive behaviors from their students. Such behaviors are derived from na environment where the teacher usually uses authoritari/an ways to solve the problems faced in the daily school life, putting their students in situations of humiliation, exposure or pure obedience to the authority, without letting them think about the solutions that take into account their needs, I.e., in assertive styles of conflict resolution. From such reason, this research tried to investigate what forms of conflict resolution are commonly used by adolescents, even from hypothetical dilemmas, and face them to the ways that teachers identified as being the ones that adolescents used in conflict situations. The sample consisted in a total of thirty-nine participants, preadolescents from eleven to thirteen years old, students in the sixth year of a public school in Campinas, countryside of São Paulo, and five teachers of these adolescents. The instrument used was a semi-structured interview with teachers and an instrument created by Robert Deluty and adapted by Maria Isabel Leme that evaluates simultaneously and comparatively three types of trends of interpersonal conflicts resolution - aggressive, assertive and submissive - in the responses of pre-adolescents to hypothetical interpersonal conflicts whose contents are of provocations, losses, frustrations etc. The results allow us to prove our hypothesis that the way adolescents in hypothetical situations solve their conflicts does not coincide with those pointed out by the teachers. These adolescents are more prone to submissive styles of conflict resolution that assertive or aggressive ways. / Doutorado / Psicologia Educacional / Doutor em Educação

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Étant donné que le mandarin est une langue dépourvue de morphologie verbale, il est difficile de démontrer l’existence du nœud T et de l’opposition entre la finitude et la non-finitude. Dans ce mémoire, nous analysons cette difficulté sous l’angle de l’interface sémantique-syntaxique. Suivant Klein (1998,2000), la finitude est porteuse de deux éléments sémantiques : le temps topique (TT) et l’assertion (AST). En mandarin, les particules d’aspect encodent le TT et l’AST. Les phrases déclaratives comprenant une particule d’aspect sont finies et les phrases déclaratives sans particule d’aspect sont non finies. En nous basant sur la structuration de la périphérie gauche (Rizzi 1997) révisée par Paul (2015) pour le mandarin, nous démontrons que les complétives déclaratives finies projettent jusqu’à TopicP, alors que les complétives déclaratives non finies projettent au TP. Le temps et la finitude ne sont pas fusionnés sous la même projection en mandarin. De plus, la finitude et la non-finitude s'analysent mieux en termes de distinction structurelle dans le cas du mandarin. / Since Mandarin is a language without verbal morphology, it is difficult to demonstrate the existence of the T-node and the opposition between finiteness and non-finiteness. In this thesis, we analyze this difficulty from the perspective of the semantic-syntactic interface. According to Klein (1998, 2000), finiteness is the carrier of two semantic elements: topic time (TT) and assertion (AST). In Mandarin, aspect particles encode TT and AST. Declarative sentences containing an aspect particle are finite and declarative sentences without an aspect particle are non-finite. Based on the left periphery structuring (Rizzi 1997) revised by Paul (2015) for Mandarin, we will demonstrate that finite declarative complements project to TopicP, while non-finite declarative complements project to TP. Time and finiteness are not assimilated under the same projection in Mandarin. Moreover, finiteness and non-finiteness are better interpreted via a structural distinction in the case of Mandarin.

Esta tesis propone una metodología de análisis dinámico que mejora el diagnóstico de programas erróneos escritos en el lenguaje Maude. La idea clave es combinar técnicas de verificación de aserciones en tiempo de ejecución con la fragmentación dinámica de trazas de ejecución para detectar automáticamente errores en tiempo de ejecución, al tiempo que se reduce el tamaño y la complejidad de las trazas a analizar. En el caso de violarse una aserción, se infiere automáticamente el criterio de fragmentación, lo que facilita al usuario identificar rápidamente la fuente del error. En primer lugar, la tesis formaliza una técnica destinada a detectar automáticamente eventuales desviaciones del comportamiento deseado del programa (síntomas de error). Esta técnica soporta dos tipos de aserciones definidas por el usuario: aserciones funcionales (que restringen llamadas a funciones deterministas) y aserciones de sistema (que especifican los invariantes de estado del sistema). La técnica de verificación dinámica propuesta es demostrablemente correcta en el sentido de que todos los errores señalados definitivamente delatan la violación de las aserciones. Tras eventuales violaciones de aserciones, se generan automáticamente trazas fragmentadas (es decir, trazas simplificadas pero igualmente precisas) que ayudan a identificar la causa del error. Además, la técnica también sugiere una posible reparación para las reglas implicadas en la generación de los estados erróneos. La metodología propuesta se basa en (i) una notación lógica para especificar las aserciones que se imponen a la ejecución; (ii) una técnica de verificación aplicable en tiempo de ejecución que comprueba dinámicamente las aserciones; y (iii) un mecanismo basado en la generalización (ecuacional) menos general que automáticamente obtiene criterios precisos para fragmentar trazas de ejecución a partir de aserciones falsificadas. Por último, se presenta una implementación de la técnica propuesta en la herramienta de análisis dinámico basado en aserciones ABETS, que muestra cómo es posible combinar el trazado de las propiedades asertadas del programa para obtener un algoritmo preciso de análisis de trazas que resulta útil para el diagnóstico y la depuración de programas. / This thesis proposes a dynamic analysis methodology for improving the diagnosis of erroneous Maude programs. The key idea is to combine runtime assertion checking and dynamic trace slicing for automatically catching errors at runtime while reducing the size and complexity of the erroneous traces to be analyzed (i.e., those leading to states that fail to satisfy the assertions). In the event of an assertion violation, the slicing criterion is automatically inferred, which facilitates the user to rapidly pinpoint the source of the error. First, a technique is formalized that aims at automatically detecting anomalous deviations of the intended program behavior (error symptoms) by using assertions that are checked at runtime. This technique supports two types of user-defined assertions: functional assertions (which constrain deterministic function calls) and system assertions (which specify system state invariants). The proposed dynamic checking is provably sound in the sense that all errors flagged definitely signal a violation of the specifications. Then, upon eventual assertion violations, accurate trace slices (i.e., simplified yet precise execution traces) are generated automatically, which help identify the cause of the error. Moreover, the technique also suggests a possible repair for the rules involved in the generation of the erroneous states. The proposed methodology is based on (i) a logical notation for specifying assertions that are imposed on execution runs; (ii) a runtime checking technique that dynamically tests the assertions; and (iii) a mechanism based on (equational) least general generalization that automatically derives accurate criteria for slicing from falsified assertions. Finally, an implementation of the proposed technique is presented in the assertion-based, dynamic analyzer ABETS, which shows how the forward and backward tracking of asserted program properties leads to a thorough trace analysis algorithm that can be used for program diagnosis and debugging. / Esta tesi proposa una metodologia d'anàlisi dinàmica que millora el diagnòstic de programes erronis escrits en el llenguatge Maude. La idea clau és combinar tècniques de verificació d'assercions en temps d'execució amb la fragmentació dinàmica de traces d'execució per a detectar automàticament errors en temps d'execució, alhora que es reduïx la grandària i la complexitat de les traces a analitzar. En el cas de violar-se una asserció, s'inferix automàticament el criteri de fragmentació, la qual cosa facilita a l'usuari identificar ràpidament la font de l'error. En primer lloc, la tesi formalitza una tècnica destinada a detectar automàticament eventuals desviacions del comportament desitjat del programa (símptomes d'error). Esta tècnica suporta dos tipus d'assercions definides per l'usuari: assercions funcionals (que restringixen crides a funcions deterministes) i assercions de sistema (que especifiquen els invariants d'estat del sistema). La tècnica de verificació dinàmica proposta és demostrablement correcta en el sentit que tots els errors assenyalats definitivament delaten la violació de les assercions. Davant eventuals violacions d'assercions, es generen automàticament traces fragmentades (és a dir, traces simplificades però igualment precises) que ajuden a identificar la causa de l'error. A més, la tècnica també suggerix una possible reparació de les regles implicades en la generació dels estats erronis. La metodologia proposada es basa en (i) una notació lògica per a especificar les assercions que s'imposen a l'execució; (ii) una tècnica de verificació aplicable en temps d'execució que comprova dinàmicament les assercions; i (iii) un mecanisme basat en la generalització (ecuacional) menys general que automàticament obté criteris precisos per a fragmentar traces d'execució a partir d'assercions falsificades. Finalment, es presenta una implementació de la tècnica proposta en la ferramenta d'anàlisi dinàmica basat en assercions ABETS, que mostra com és possible combinar el traçat cap avant i cap arrere de les propietats assertades del programa per a obtindre un algoritme precís d'anàlisi de traces que resulta útil per al diagnòstic i la depuració de programes. / Sapiña Sanchis, J. (2017). Rewriting Logic Techniques for Program Analysis and Optimization [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/94044

Summaries in English and Afrikaans / Text in Afrikaans / Until 1988, hearsay-evidence in our legal system was governed by common law. During this period resistance developed regarding the practice that hearsay which complied with certain exceptions could indeed be allowed. Case law excluded further exceptions being added. Legislation was enacted in 1988 in which hearsay was defined, a total exclusionary rule retained, but the Courts given a wide discretion to allow hearsay. Via this legislation a more accommodating stance towards hearsay was introduced. This dissertation aimed at measuring whether the legislation achieved its objectives and consisted of analysing case law and interviewing Judges and Advocates. The conclusion arrived at is that the legislation has only marginally changed the usage of hearsay in our legal system. The major obstacle lies in the attitude of practitioners who continue to distrust hearsay and do not utilize the mechanism provided by statute. / Tot en met 1988, is hoorse-getuienis in ons regstelsel gemeenregtelik beheer. In die tydperk bet besware egter geleidelik ontwikkel veral oor die gekunstelde wyse waarop hoorsê as aan bepaalde uitsonderings voldoen is wel toegelaat is. Regspraak het voorts ook bepaal dat geen verdere uitsonderings toegevoeg kon word nie. In 1988 is wetgewing uitgevaardig waarin hoorsê-getuienis omskryf word, 'n algehele uitsluitingsreel behou word maar aan die howe 'n wye diskresie verleen word om na oorweging van voorgeskrewe faktore, hoorsê wei toe te laat. Die oogmerk van hierdie wetgewing was om 'n meganisme daar te stel om soos by die civil regstelsels en sekere ander Iande, 'n meer toeskietlike houding jeens hoorsê te bewerkstellig. Hierdie verhandeling se hoofdoel was om te bepaal of die wetgewing in die doel geslaag bet. Om tot 'n bevinding te kom is regspraak ontleed, en is onderhoude gevoer beide met Regters en die Advokatuur. Die slotsom bereik dui daarop dat die wetgewing maar weinig verander bet in die gebruikmaking van hoorse-getuienis in ons regstelsel. Wat die wetgewing self betref, hoewel daar sekere besware te make is oor sekere bepalings, verskaf dit tog 'n bruikbare instrument. Die grootste struikelblok is gelee in die instelling van die praktisyns wat bly vasklou aan 'n gevestigde vrees vir hoarse en nie gebruikmaak van die nuwe geleentheid nou deur die wetgewing daargestel nie. / Law / LL.M.

O objetivo desta tese é analisar, em uma perspectiva comparada, como nascem, evoluem e são frustrados três projetos de democratização radical na América Latina nos primórdios do imperialismo. José Martí (1853-1895) em Cuba, Juan B. Justo (1865- 1928) na Argentina e Ricardo Flores Magón (1874-1922) no México, lideram esforços intelectuais e políticos orientados a superar os constrangimentos à integração nacional legados pela origem colonial, que se expressam em um pensamento que fundamenta a atuação dos partidos que dirigiram. Vivendo no contexto de difusão das relações de produção capitalistas no continente, estes projetos constituem esforços pioneiros de subordinar o desenvolvimento capitalista aos desígnios da sociedade nacional. A incidência que tiveram para o desencadeamento dos processos que objetivaram a guerra da independência em Cuba, a reforma política na Argentina e a Revolução Mexicana - atesta a sintonia de suas propostas em relação aos dilemas que enfrentaram. O malogro do ideário democrático que representavam indica a prevalência de constrangimentos estruturais que obstam a consumação da nação na América Latina naquela circunstância. Partindo da premissa de que os autores analisados constituem expoentes do pensamento e da política radical em suas conjunturas, nossa hipótese é que a aproximação entre os três casos sugere as balizas que referenciavam a máxima consciência possível no campo da militância democrática no continente naquele contexto histórico. / This research aims to analyse, on a comparative perspective, the rising, evolution and eventual frustration of three projects of radical democratization in Latin America in the beginnings of imperialism. José Martí (1853-1895) in Cuba, Juan B. Justo (1865-1928) in Argentina and Ricardo Flores Magón (1874-1922) in México, led intelectual and political efforts aiming to ovecome the constraints inherited from the colonial past as a premise to assert national integration. an effort that was expressed in their thoughts, which in turn have shaped the political parties which they led. This purpose has been expressed on their thought, which in turn has shaped the political parties they conducted. Living in the context of difusion of capitalist production relations in the continent, these projects constitute pioneer attempts to subordinate the capitalist development to the design of national society. The fact that their political activity contributed to unleash the processes which they aimed to the War of Independence in Cuba, political reform in Argentina and the Mexican Revolution attests that their proposals were well tuned to the dilemmas they faced. The failure to impose the democratic ideals which they represented points to the prevalence of structural constrains that hinder the consumation of the nation in Latin America on that circumstance. Assuming as a premise that the authors analysed in this work are exponents of radical thought and politics in their conjunctures, our hypothesis is that the approach of the three cases suggest the boundaries that referred the maximum posible consciousness of democratic militancy in the continent in that historical context.

Les travaux présentés dans cette thèse visent à produire automatiquement des prototypes de circuits de communication et de contrôle à partir de spécifications temporelles déclaratives. Partant d'un ensemble de propriétés écrites en langage PSL, nous produisons un modèle RTL synthétisable automatiquement. La méthode proposée est modulaire, contrairement aux méthodes publiées antérieurement qui étaient fondées sur la théorie des automates. Pour chaque propriété, nous produisons un composant qui observe certains opérandes et génère des chronogrammes pour les autres opérandes : le module réactif. Tout d'abord, une bibliothèque des modules réactifs primitifs a été développée pour les opérateurs FL et SERE. Pour ce faire, une relation de dépendance a été définie pour chaque opérateur : fondée sur la sémantique de l'opérateur, elle exprime la dépendance entre ses opérandes. Ensuite, la relation de dépendance de chaque opérateur est interprétée comme un composant matériel qui met en œuvre l'opérateur : c'est le module réactif primitif de l'opérateur. À l'aide de cette formalisation, nous proposons une méthode pour déterminer automatiquement quels signaux d'une propriété sont observés et lesquels sont générés. Dans le cas où il n'est pas possible de déterminer le sens du signal, un solveur est ajouté pour identifier la valeur du signal. Le solveur sert aussi à déterminer la valeur d'un signal généré par plusieurs propriétés. Le circuit final est l'interconnexion des modules réactifs et des solveurs pour l'ensemble des propriétés. Un outil prototype, SyntHorus2, qui est une extension d'HORUS, a été mis développé. Il prend les propriétés PSL comme entrées et génère le code VHDL synthétisable du circuit. En outre, il génère des propriétés complémentaires pour vérifier si l'ensemble des spécifications est cohérent et complet. La méthode est efficace et synthétise des circuits de commande en quelques secondes. Les résultats que nous avons obtenus sur des jeux d'essais classiques montrent que notre technique compile les propriétés plus efficacement que les outils prototypes qui l'ont précédée. / The work presented in this thesis aims at automatically prototype communication and control designs from declarative temporal specifications. From a set of PSL properties, we produce a synthesizable RTL design automatically. The proposed method is modular, in contrast to previously published methods that were based on automata theory. From each property, we produce a component that observes some operands and generates waveforms for the other operands: the reactant. First, a library of primitive reactants has been provided for FL and SERE operators. To this goal, a dependency relation is defined for each operator that expresses the dependency among its operands using the operator's semantics. Then, the dependency relation of each operator is interpreted as a hardware component that implements the operator: the operator's primitive reactant. Using this formalization, a method is proposed to automatically decide which signals of a property are observed and which are generated. In the cases when specifying the signal direction is not possible, a solver is implemented to identify the signal value. In addition, the way of identifying the value of the signal that is generated in several properties is addressed. The final circuit is the interconnection of the properties' reactants and solvers. A prototype tool SyntHorus2, which is an extension to HORUS, has been developed. It takes PSL properties as its inputs, and generates the synthesizable VHDL code of the circuit. In addition, it generates some complementary properties to verify if the set of specification is coherent and complete. The method is efficient, and synthesizes control circuits in a few seconds. Results obtained on classical benchmarks show that our technique compiles properties more efficiently than previous prototype tools.

Dans cette thèse, je propose trois contributions principales : dans notre première contribution, nous étudions l'architecture d'identité WebRTC et plus particulièrement son intégration aux algorithmes de délégation d'authentification existants. Cette intégration n'a pas encore été étudiée jusqu'à présent. Dans cette perspective, nous implémentons les composants de l'architecture d'identité WebRTC ce qui nous permet de montrer que cette architecture n'est pas particulièrement adaptée à une intégration aux protocoles de délégation d'authentification existants tels qu'OpenID Connect. Pour répondre à RQ1, nous montrons ensuite comment la position centrale des fournisseurs d'identité dans l'écosystème du Web est renforcée par leur intégration à l'établissement de session WebRTC, posant ainsi un risque supplémentaire contre la discrétion des utilisateurs. Dans l'écosystème Web, la norme est l'architecture des services en silo dont les utilisateurs sont captifs. C'est en particulier le cas des systèmes de délégation d'authentification, pour lesquels la plupart du temps, il n'est pas possible de choisir son fournisseur d'identité. Afin de répondre à RQ3, nous réalisons une étude afin de déterminer pour quelles raisons les utilisateurs ne peuvent pas choisir leur fournisseur d'identité sur Web. Notre étude montre que bien que ce choix soit possible en théorie, l'absence d'implémentation de certains standards par les sites webs et les fournisseurs d'identité empêche ce choix en pratique. Dans notre seconde contribution, nous cherchons à donner plus de contrôle à l'utilisateur. Pour ce faire et en réponse à RQ2, nous proposons une extension de la spécification WebRTC afin de permettre la négociation des paramètres d'identité. Un prototype d'implémentation est proposé afin de valider notre proposition. Cette implémentation révèle certaines limites dues à l'API d'identité WebRTC empêchant notamment d'obtenir un retour sur le niveau d'authentification de l'autre utilisateur ainsi que l'impossibilité de changer de fournisseur d'identité en cours de session. Nous proposons ensuite une API Web permettant aux utilisateurs de choisir leur fournisseur d'identité lors d'une authentification sur un site tiers via une interface de sélection d'identité contrôlée par le navigateur. Répondant à RQ3, notre API repose sur une réutilisation de l'architecture d'identité WebRTC dans un scénario client-serveur. Nous présentons une implémentation de notre solution, basée sur une extension du navigateur Firefox, afin d'en démontrer l'utilisabilité. Nos résultats montrent qu'à long terme, l'adoption de cette API pourrait réduire la charge d'implémentation pour les développeurs de sites Web et permettre aux utilisateurs de préserver leur discrétion en choisissant des fournisseurs d'identité de confiance. / In this thesis, we propose three main contributions : In our first contribution we study the WebRTC identity architecture and more particularly its integration with existing authentication delegation protocols. This integration has not been studied yet. To fill this gap, we implement components of the WebRTC identity architecture and comment on the issues encountered in the process. In order to answer RQ1, we then study this specification from a privacy perspective an identify new privacy considerations related to the central position of identity provider. In the Web, the norm is the silo architecture of which users are captive. This is even more true of authentication delegation systems where most of the time it is not possible to freely choose an identity provider. In order to answer RQ3, we conduct a survey on the top 500 websites according to Alexa.com to identify the reasons why can't users choose their identity provider. Our results show that while the choice of an identity provider is possible in theory, the lack of implementation of existing standards by websites and identity providers prevent users to make this choice. In our second contribution, we aim at giving more control to users. To this end and in order to answer RQ2, we extend the WebRTC specification to allow identity parameters negotiation. We present a prototype implementation of our proposition to validate it. It reveals some limits due to the WebRTC API, in particular preventing to get feedback on the other peer's authentication strength. We then propose a web API allowing users to choose their identity provider in order to authenticate on a third-party website, answering RQ2. Our API reuse components of the WebRTC identity architecture in a client-server authentication scenario. Again, we validate our proposition by presenting a prototype implementation of our API based on a Firefox extension. Finally, in our third contribution, we look back on RQ1 and propose a trust and security model of a WebRTC session. Our proposed model integrates in a single metric the security parameters used in the session establishment, the encryption parameters for the media streams, and trust in actors of the communication setup as defined by the user. Our model objective is to help non-expert users to better understand the security of their WebRTC session. To validate our approach, we conduct a preliminary study on the comprehension of our model by non-expert users. This study is based on a web survey offering users to interact with a dynamic implementation of our model.