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Les moteurs de recherche exploratoire (MRE) sont des logiciels aidant les utilisateurs à explorer un domaine d’intérêt pour y faire des découvertes. Ces moteurs se distinguent en cela des moteurs de recherche classiques tels que Google, Bing ou Yahoo!, lesquels supportent plutôt des recherches ciblées ou recherches de consultation (lookup). Si l’on admet que l’évaluation des MRE vise à vérifier si ces derniers aident effectivement les utilisateurs à réaliser leur tâche d’exploration, on constate que les méthodes existantes d’évaluation de ces systèmes ne permettent pas réellement cette vérification. L’une des raisons à cela est que ces méthodes ne reposent pas sur un modèle approprié de la recherche exploratoire (RE) ou qu’elles restent accrochées à un modèle de la recherche de consultation. L’objectif principal de cette thèse est de proposer aux concepteurs de ces MRE des méthodes d’évaluation centrées utilisateurs reposant sur un modèle du processus de RE. Ainsi, après avoir modélisé le processus de RE, nous proposons deux méthodes d’évaluation qui peuvent être utilisées tout au long du processus de conception. La première méthode, une méthode d’inspection sans utilisateurs, peut être utilisée dès les premières maquettes, et repose sur des heuristiques de RE. Nous avons également proposé des outils facilitant l’utilisation de ces heuristiques : un formulaire en ligne ainsi qu’une extension Google Chrome appelée CheXplore. La seconde méthode, avec utilisateurs, peut être utilisée dès la première version d’un prototype fonctionnel. Cette méthode se présente comme une procédure de test utilisateur personnalisable. Dans cette thèse, nous nous intéressons plus particulièrement à deux éléments de cette procédure : un protocole d’élaboration de tâches de RE et une grille d’analyse d’enregistrements vidéo de session de RE. La pertinence du modèle ainsi que les méthodes qui en découlent ont été évaluées à l’occasion de tests utilisateurs. Le modèle, les heuristiques et le protocole d’élaboration des tâches de RE ont été validés. Les premières évaluations de la grille d’analyse d’enregistrements vidéos ont révélé des points à améliorer. / Exploratory search systems are search engines that help users to explore a topic of interest. A shortcoming of current evaluation methods is that they cannot be used to determine if an exploratory search system can effectively help the user in performing exploratory search tasks. Indeed, the assessment cannot be the same between classic search systems (such as Google, Bing, Yahoo!...) and exploratory search systems. The complexity and the difficulty to have a consensus definition of the exploratory search concept and process are reflected in the difficulties to evaluate such systems. Indeed, they combine several specifics features and behaviors forming an alchemy difficult to evaluate. The main objective of this thesis is to propose for the designers of these systems (i.e. computer scientists) user-centered evaluation methods of exploratory search systems. These methods are based on a model of exploratory search process in order to help the evaluators to verify if a given system supports effectively the exploratory search process. Thus, after elaborating a model of exploratory search process, we propose two model-based methods, with and without users, which can be used all along the design process. The first method, without users, can be used from the first sketch of the system, consists of a set of heuristics of exploratory search and a procedure for using them. We also propose two tools facilitating their use: an online form format and an Google Chrome plugin, CheXplore. The second method involves real end-users of exploratory search systems who test a functional prototype or version of an exploratory search system. In this thesis, we mainly focus on two model-based elements of a customizable user testing procedure: a protocol for the elaboration of exploratory search tasks and a video analysis grid for the evaluation of recorded exploratory search sessions.

The thesis deals with issue of international double taxation with respect to taxes on income and capital. The aim of the thesis is to provide a comprehensive overview of the issue of concluding international double tax treaties and to verify, whether the differences in their provisions can be significant enough to affect activities of internationally active entities. The body of the thesis is divided into three chapters. The first chapter explains what double taxation is, how it occurs and the possible ways of its elimination. It also deals with related tax evasion. The second chapter is devoted to bilateral and multilateral tax treates. The emphasis is on OECD and UN model conventions and related issues of exchange of information, non-discrimination and dispute resolution. The third chapter focuses on the approach of the Czech republic to enter into tax treaties. Its main part is devoted to a comparison of tax treaties which the Czech republic has concluded with the United States of America, Slovakia and Germany.

This dissertation interrogates which principles should govern the interpretation of South African Double Tax Agreements (‘DTAs’). This field of study is complex because any DTAs have a dual nature. In the first place, it is an international agreement where two states are parties (a bilateral agreement); second, it also becomes part of domestic law. DTAs are governed by principles of customary international law some of which have been codified in the Vienna Convention on the Law of Treaties (‘VCLT’). Though South Africa is not a party to the VCLT, nevertheless, there is judicial support in South Africa for the notion that VCLT reflects general principles of international law [Harksen v President of the Republic of South Africa 1998 (2) SA 1011 (C)]. DTAs are incorporated into South African domestic law by way of statutory enactment in accordance with the dualist approach to international law. The first purpose of the dissertation is to systematise and analyse the structure of an OECD Model Tax Convention (‘OEC D MTC’) and the international methods (principles) of interpretation of DTAs in order to gain a better understanding of how this international methods functions. A number of issues relating to the interpretation of these methods are analysed. Since DTAs are applied by tax authorities, courts and taxpayers in a domestic law context, i.e. within the framework of the legal system of a particular state, the analysis focuses on the application in South Africa of the methods of the interpretation of South African DTAs. The second objective of the dissertation refers to international tax law principles (treaties and customary international law) derived from South Africa public international law and to evaluate a few selected issues related to South African DTAs and their relevance to South Africa domestic tax laws; the interpretation of DTAs and the implications of a DTA overriding or in conflict with South Africa domestic tax laws. It will also interrogate the legal status of a DTA under South African tax law and whether the anti-discrimination article in South Africa DTAs have the force of law in South Africa? / Dissertation (LLM)--University of Pretoria, 2014. / gm2014 / Mercantile Law / unrestricted