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Access control models, such as the ones supported by commercial DBMSs, are not yet able to fully meet many application needs. An important requirement derives from the temporal dimension that permissions have in many real-world situations. Permissions are often limited in time or may hold only for specific periods of time. In this article, we present an access control model in which periodic temporal intervals are associated with authorizations. An authorization is automatically granted in the specified intervals and revoked when such intervals expire. Deductive temporal rules with periodicity and order constraints are provided to derive new authorizations based on the presence or absence of other authorizations in specific periods of time. We provide a solution to the problem of ensuring the uniqueness of the global set of valid authorizations derivable at each instant, and we propose an algorithm to compute this set. Moreover, we address issues related to the efficiency of access control by adopting a materialization approach. The resulting model provides a high degree of flexibility and supports the specification of several protection requirements that cannot be expressed in traditional access control models.

OMNIFACE is an object-based environment that assists the user in the preparation of the input files for quantum-chemical programs. These programs share the same conceptual domain, but the formalisms used to set up the desired computation are different from one application to the other. In order to set up the computation, the user has to prepare an input file containing the values for a number of different parameters. This task can be very complex because of the large number of parameters to choose from and because of the constraints existing among them. A constraint violation can lead to a job abortion or to wrong results. OMNIFACE supplies a uniform and friendly environment that allows the user to experiment with possible configurations of parameters and with different applications. It includes a domain model that is used to specify the desired computation working on concepts typical of computational chemistry. A distributed object-oriented constraint checking system ensures the overall consistency of the resultant input file. >

In the recent years several research efforts have focused on the concept of time granularity and its applications. A first stream of research investigated the mathematical models behind the notion of granularity and the algorithms to manage temporal data based on those models. A second stream of research investigated symbolic formalisms providing a set of algebraic operators to define granularities in a compact and compositional way. However, only very limited manipulation algorithms have been proposed to operate directly on the algebraic representation making it unsuitable to use the symbolic formalisms in applications that need manipulation of granularities. This paper aims at filling the gap between the results from these two streams of research, by providing an efficient conversion from the algebraic representation to the equivalent low-level representation based on the mathematical models. In addition, the conversion returns a minimal representation in terms of period length. Our results have a major practical impact: users can more easily define arbitrary granularities in terms of algebraic operators, and then access granularity reasoning and other services operating efficiently on the equivalent, minimal low-level representation. As an example, we illustrate the application to temporal constraint reasoning with multiple granularities. From a technical point of view, we propose an hybrid algorithm that interleaves the conversion of calendar subexpressions into periodical sets with the minimization of the period length. The algorithm returns set-based granularity representations having minimal period length, which is the most relevant parameter for the performance of the considered reasoning services. Extensive experimental work supports the techniques used in the algorithm, and shows the efficiency and effectiveness of the algorithm.

The heterogeneity of device capabilities, network conditions and user contexts that is associated with mobile computing has emphasized the need for more advanced forms of adaptation of Internet services. This paper presents a framework that addresses this issue by managing distributed profile information and adaptation policies, solving possible conflicts by means of an inference engine and prioritization techniques. The profile information considered in the framework is very broad, including user preferences, device and network capabilities, and user location and context. The framework has been validated by experiments on the efficiency of the proposed conflict resolution mechanism, and by the implementation of the main components of the architecture. The paper also illustrates a specific testbed application in the context of proximity marketing.

An effort has been devoted in the recent years to study and formalize the concept of time granularity and to design applications and services using the formalization. Among other proposals, a calendar algebra has been defined to facilitate the specification of new granularities and to perform conversions among them. This paper shows how granularities defined as algebraic calendar expressions can be represented as periodical sets of instants. More precisely the paper shows how each algebraic operator changes the periodical structure of the granularities given as operands. These results have an immediate application enabling users to easily specify new granularities and using them in the only constraint solver supporting time granularities that is currently available.

This paper considers temporal constraints that can impose a minimum and maximum time distance between the occurrences of two events by specifying the minimum and maximum values in terms of a time granularity. When several constraints using different time granularities are part of the specification of a single problem, a reasonable question is how to convert the constraints in terms of a single granularity in order to apply standard temporal constraint algorithms. This paper investigates the problem of converting a distance constraint expressed in terms of a granularity into another one in terms of a different time granularity. An expressive formal model for time granularities is assumed including common granularities like hours and days as well as user-defined granularities like business days and academic semesters.

Esta tese apresenta os resultados da modelagem geoestatística do depósito de apatita de Araxá. Nesse sentido, as técnicas de estimativa e simulação foram extensivamente aplicadas aos dados analíticos disponíveis desse depósito. Além disso, a aplicação da variância de interpolação para fins de planejamento de lavra é também discutida. O depósito de apatita de Araxá localiza-se na porção oeste do Estado de Minas Gerais e resulta da atuação de processos de intemperismo sobre as diferentes rochas do Complexo Alcalino-Carbonatítico de Araxá de idade Cretácea. O manto de intemperismo apresenta duas zonas: um capeamento estéril e uma zona mineralizada à apatita. Em termos tecnológicos, foram definidos vários tipos de minério de apatita. Contudo, neste estudo somente os dois tipos mais importantes foram considerados, que são: os tipos normal e micáceo. Assim, os dados provenientes desses tipos de minério foram submetidos aos processamentos por técnicas geoestatísticas de estimativa e simulação, objetivando estudar a distribuição espacial, assim como as incertezas associadas às estimativas e aos resultados de simulações. Como método de estimativa, a krigagem ordinária foi escolhida em função das suas características superiores em relação a outras técnicas de krigagem, como a krigagem simples. Por outro lado, dentre as várias técnicas de simulação disponíveis, somente a simulação gaussiana seqüencial e por bandas rotativas foram aplicadas, pois estes algoritmos produzem resultados mais compatíveis com os dados de entrada. Os resultados da estimativa e das simulações são muito próximos entre si, mas as incertezas associadas à krigagem ordinária, aproximada pela variância de interpolação, são sempre maiores que aquelas associadas às realizações de simulações estocásticas. A separação do minério em tipos tecnológicos foi importante, pois proporcionou resultados melhores e mais precisos no cálculo dos variogramas e, conseqüentemente, na modelagem geoestatística. A variância de interpolação revelou ser uma ferramenta importante para o auxílio ao planejamento de lavra, à medida que ela proporciona uma boa idéia da variabilidade espacial. Nesse sentido, áreas com maiores incertezas deveriam ser desenvolvidas com maior cuidado, incluindo-se aí a necessidade de amostragem adicional, a fim de evitar erros na classificação de minérios e rejeito. Finalmente, esta tese mostrou a importância da caracterização tecnológica em tipos de minério que aprimora os resultados da modelagem geoestatística. Results of a geostatistical modeling of the Araxá apatite deposit are presented in this thesis. In this sense, estimation and simulation techniques were extensively applied to the chemical data available for this deposit. Besides, application of the interpolation variance for mining planning purposes is also discussed. The Araxá apatite deposit is located in the western portion of Minas Gerais State and results from weathering processes on different rocks from the Araxá Alkaline-Carbonatitic Complex of Cretaceous age. The weathering mantle presents two zones, an uppermost overburden level and an apatite bearing zone. For mining purposes, several apatite ore types were identified. However, in this study only the most important ore types were considered, i.e., normal and micaceous types. Thus, data coming from these ore types were submitted to geostatistical estimation and simulation techniques in order to study the spatial distribution as well as uncertainties associated with estimates and simulated results. As an estimation method the ordinary kriging technique was chosen because of its superior characteristics in relation to other kriging techniques such as simple kriging. On the other hand, among several simulation techniques available, only sequential Gaussian and turning bands simulation techniques were applied because they produce results more compatible with input data. Estimation and simulation produce results close to each other, but uncertainties associated with ordinary kriging estimates, as approximated by the interpolation variance, are always greater than those associated with stochastic simulation realizations. Separation of ore types into technological classes was important as long as it provided better and more precise results for computing variograms and, consequently, for geostatistical modeling. The interpolation variance revealed to be an important tool for mine planning as long as it gives a good idea of the spatial variability. In this sense, areas with greater uncertainty should be developed carefully, in order to avoid misclassification between ore and waste. Finally, this thesis showed the importance of applied mineralogy into ore which improves the results of geostatistical modeling.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR O estudo da variabilidade das propriedades dos solos, como resistência de ponta (qc), resistência não drenada (Su) e poro pressão (∆u), é a principal meta desta tese. Utilizam-se de técnicas de Probabilidade e Estatística em ensaios in situ como piezocone, palheta e pressiométricos tipo Menard e Auto-Perfurante. Em um primeiro momento, os resultados de Su são analisados através de retas médias obtidas pela comparação dos resultados de Su, em depósitos em que o teor de umidade é maior ou igual ao limite de liquidez e em depósitos em que a umidade é menor que o limite de liquidez. A determinação da Função Densidade de Probabilidade (FDP) para os ensaios de piezocone em solo residual - Campus Experimental da PUC-RIO, argila mole da Baixada Santista e na Barragem de Rejeito de Ouro em Paracatu - MG, também será objeto de estudo a melhor FDP, entre a Normal e a Lognormal.E por fim, estuda-se o parâmetro chamado escala de flutuação que, juntamente com a média e o desvio-padrão, descreve com maior eficiência a variabilidade espacial das propriedades dos solo, utilizando-se de duas metodologias: uma para o ensaio de piezocone, baseada no modelo de campo aleatório proposta por Vanmarcke, e a outra para os ensaios palheta e pressiômetros Menard e Auto-Perfurante, através do estudo da função de autocorrelação, baseada no trabalho de Asaoka e Grivas. It is well known that there is an inherent variability in the values of undrained shear strength of soil collected at different depths. In the case of natural deposits, this variability is attributed to the randomness associated with the geological processes involved in the formation of the deposits. The study on spatial variability of soil properties like undrained shear strength (Su), cone bearing (qc) and pore pressure(delta u), is the main goal of this thesis. Probabilistic and Statistical approaches have been applied to analyze results of cone penetration tests performed in quartenary soft clay deposits located in the Baixada Santista - Sao Paulo, gneiss residual soil profile - Experimental Campus - PUC-RIO and also in a Tailing dam at Paracatu - MG. Vane, Menard and self-boring Pressuremeter tests have been used to establish the scale of fluctuation through the study of autocorrelation functions in a quartenary soft clay deposit located in the Baixada Santista area. The results of that study have shown that, for piezocone tests in the residual soil and soft clay in the Baixada Santista, the best Probability Density Function will be Lognormal, and that fluctuation scale obtained from piezocone, Vane, Menard and self-boring pressuremeter tests are an important descriptor of soil variability. El estudio de la variabilidad de las propriedades de los suelos tales como resistencia de punta (qc), resistencia no drenada (Su) y poro presión (∆u), es la meta principal de esta tesis. Este estudio utiliza técnicas de probabilidades y estadística en ensayos in situ como piezocone, Paleta, presiometros Menard y Auto-Perforante. En un primer momento, se analizan los resultados de Su a través de rectas médias obtenidas por comparación de los resultados de Su, en depósitos donde la humedad es mayor o igual al Límite de Líquidez y en depósitos en que la humedad es menor que el límite de líquidez. La determinación de la Función de Densidad de Probabilidad (FDP) para los ensayos de piezocone en suelo residual - Campo Experimental de la PUC-RIO, arcilla blanda de la Baixada Santista y en Barragem de Rejeito de Ouro, en Paracatu - MG, también será objeto de estudio la mejor FDP, entre la Normal y la Lognormal. Y por fin, el estudio del parámetro llamado escala de fluctuación que, conjuntamente con la media y el error estándar descriven com mayor eficiencia la variabilidad espacial de las propriedades de los suelos, haciendo uso de dos metodologías. Una para el ensayo de piezocone y la otra para los ensayos Paleta, presiometros Menard y Auto-Perforante a través del estudio de la función de autocorrelación.