Organizações Virtuais constituem uma modalidade de cooperação entre empresas com contornos inovadores, especialmente no que diz respeito aos seus processos de configuração, dissolução e reconfiguração. Estes acontecem repetidamente em um período relativamente curto de tempo, com uma certa variabilidade de parceiros tirados de um grupo previamente articulado pela tecnologia de informação, com vistas a oportunidades únicas de negócios. Não existem modelos legais pré-concebidos que comportem isoladamente esse propósito de negócio único e que sejam simultaneamente ágeis para se adaptar a novas oportunidades sem maiores custos. A experiência internacional tem demonstrado que a utilização isolada dos mecanismos tradicionais não suporta a complexidade das relações que se estabelecem entre os parceiros, que culmina com o surgimento daquilo que passou a denominar-se Empresa Virtual. Nesse sentido são analisados os atributos mais imortantes a serem preservados nesse tipo de cooperação bem como as inúmeras possibilidades e barreiras encontradas na legislação, a fim de identificar o mecanismo mais adequado dentro da permissividade legal e adaptá-lo às novas exigências. / Virtual Organizations constitute a new model of cooperation between companies with innovator profile, especially in its configuration processes, dissolution and reconfiguration. These occurrences happen frequently in a short period of time, with some changes in partners that are removed from one group arranged before by information technology, seeking for unique business opportunities. There are no pre-concept legal model that isolated support this unique business propose and be fast enough to adapt itself to new opportunities without increasing costs. International experience has shown that isolated use of traditional mechanisms do not support the complex relation established among partners, that culminate with the arising of which is called Virtual Enterprise. By this way, the most important features to be preserved in these kind of cooperation are analyzed, as well as its uncountable possibilities and barriers found in law, to identify the most adequate legal mechanism and adapt it to new exigencies

Organizações Virtuais constituem uma modalidade de cooperação entre empresas com contornos inovadores, especialmente no que diz respeito aos seus processos de configuração, dissolução e reconfiguração. Estes acontecem repetidamente em um período relativamente curto de tempo, com uma certa variabilidade de parceiros tirados de um grupo previamente articulado pela tecnologia de informação, com vistas a oportunidades únicas de negócios. Não existem modelos legais pré-concebidos que comportem isoladamente esse propósito de negócio único e que sejam simultaneamente ágeis para se adaptar a novas oportunidades sem maiores custos. A experiência internacional tem demonstrado que a utilização isolada dos mecanismos tradicionais não suporta a complexidade das relações que se estabelecem entre os parceiros, que culmina com o surgimento daquilo que passou a denominar-se Empresa Virtual. Nesse sentido são analisados os atributos mais imortantes a serem preservados nesse tipo de cooperação bem como as inúmeras possibilidades e barreiras encontradas na legislação, a fim de identificar o mecanismo mais adequado dentro da permissividade legal e adaptá-lo às novas exigências. / Virtual Organizations constitute a new model of cooperation between companies with innovator profile, especially in its configuration processes, dissolution and reconfiguration. These occurrences happen frequently in a short period of time, with some changes in partners that are removed from one group arranged before by information technology, seeking for unique business opportunities. There are no pre-concept legal model that isolated support this unique business propose and be fast enough to adapt itself to new opportunities without increasing costs. International experience has shown that isolated use of traditional mechanisms do not support the complex relation established among partners, that culminate with the arising of which is called Virtual Enterprise. By this way, the most important features to be preserved in these kind of cooperation are analyzed, as well as its uncountable possibilities and barriers found in law, to identify the most adequate legal mechanism and adapt it to new exigencies

L’implémentation d’une étude d’événement est confrontée à des choix méthodologiques plus ou moins arbitraires concernant la période de l’étude et l’échantillon sélectionné. Or, ces choix méthodologiques conditionnent les résultats obtenus, aboutissant à des divergences notoires en matière de conclusions. Une démarche par simulations, effectuées sur des données réelles de la Bourse de Tunis, nous a permis de juger de la validité des différentes méthodes à utiliser et des différents tests à mettre en œuvre, puis de déterminer celles et ceux qui sont recommandés en fonction des caractéristiques de l’événement à étudier. Nos résultats sont spécifiquement adaptés aux marchés émergents, souffrant d’un manque de liquidité, d’un manque de transparence…En application des résultats de la méthodologie recommandée, nous avons cherché à analyser l’impact sur le marché boursier tunisien, de changements d’abord microstructurels et ensuite environnementaux de nature institutionnelle. Au plan de la microstructure, les choix organisationnels ont été répartis en trois catégories distinctes : la structure du marché, la transparence et le contrôle de la variation des prix. Au plan institutionnel, nous avons axé notre analyse sur l’infrastructure légale en considérant quatre composantes : la protection des investisseurs externes à l’entreprise, les lois sur les valeurs mobilières, les transactions des initiés et le cadre comptable. / Event studies implementation faces many arbitrary methodological choices concerning the period of the study and the selected sample. Unfortunately, these methodological choices condition the results of the study, leading to important differences in the outcomes. An approach by simulations, carried out on actual data of the Tunis stock exchange, has allowed us to judge the validity of the different methods used and the different tests to be implemented, in order to determine those recommended according to the characteristics of the event being studied. Our results are specifically adapted to the emerging markets, known for their lack of liquidity, lack of transparency…Pursuant to the results of the recommended methodology, we next analyze the impact on the Tunisian stock market, of some micro-structural and institutional changes that have occurred in the last years. In terms of microstructure, we precisely examine the structure of the market, its degree of transparency and the mechanisms of price variations control. In terms of institutional environment, we focus our analysis on the legal infrastructure through the aspects of company’s outsiders’ protection, securities law, insiders’ transactions and accounting framework.