04271 Abstracts Collection -- Preferences: Specification, Inference, Applications

From 27.06.04 to 02.07.04, the Dagstuhl Seminar 04271 ``Preferences: Specification, Inference, Applications\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

Access Control from an Intrusion Detection Perspective

Access control and intrusion detection are essential components for securing an organization's information assets. In practice, these components are used in isolation, while their fusion would contribute to increase the range and accuracy of both. One approach to accomplish this fusion is the combination of their security policies. This report pursues this approach by defining a comparison framework for policy specification languages and using this to survey the languages Ponder, LGI, SPL and PDL from the perspective of intrusion detection. We identified that, even if an access control language has the necessary ingredients for merging policies, it might not be appropriate due to mismatches in overlapping concepts

Policy representation and reasoning with preferences and reactivity

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Model-Based Contrastive Explanations for XAIP: Towards a General Model and Prototype

Planning is an important sub-field of artificial intelligence (AI) focusing on letting intelligent agents deliberate on the most adequate course of action to attain their goals. Thanks to the recent boost in the number of critical domains and systems which exploit planning for their internal procedures, there is an increasing need for planning systems to become more transparent and trustworthy. Along this line, planning systems are now required to produce not only plans but also explanations about those plans, or the way they were attained. To address this issue, a new research area is emerging in the AI panorama: eXplainable AI (XAI), within which explainable planning (XAIP) is a pivotal sub-field. As a recent domain, XAIP is far from mature. No consensus has been reached in the literature about what explanations are, how they should be computed, and what they should explain in the first place. Furthermore, existing contributions are mostly theoretical, and software implementations are rarely more than preliminary. To overcome such issues, in this thesis we design an explainable planning framework bridging the gap between theoretical contributions from literature and software implementations. More precisely, taking inspiration from the state of the art, we develop a formal model for XAIP, and the software tool enabling its practical exploitation. Accordingly, the contribution of this thesis is four-folded. First, we review the state of the art of XAIP, supplying an outline of its most significant contributions from the literature. We then generalise the aforementioned contributions into a unified model for XAIP, aimed at supporting model-based contrastive explanations. Next, we design and implement an algorithm-agnostic library for XAIP based on our model. Finally, we validate our library from a technological perspective, via an extensive testing suite. Furthermore, we assess its performance and usability through a set of benchmarks and end-to-end examples

A new basal sauropodiform from South Africa and the phylogenetic relationships of basal sauropodomorphs

We present a new medium-sized basal sauropodomorph, Sefapanosaurus zastronensis gen. et sp. nov., from the Upper Triassic−Lower Jurassic Elliot Formation of South Africa. It is represented by parts of the postcranial skeleton of at least four individuals, including: cervical, dorsal, sacral and caudal vertebrae, most of the forelimb, and part of the hindlimb. Sefapanosaurus bears several autapomorphies of the astragalus, and referred material also shows autapomorphic features. The inclusion of Sefapanosaurus in a phylogenetic analysis places it within the group of sauropodomorphs more closely related to sauropods than to Massospondylus (i.e. Sauropodiformes), increasing the currently known diversity of the so-called ‘transitional forms’ leading to Sauropoda. Character optimization revealed the presence of several features that are common for taxa placed within the transitional branches basal to Sauropoda. Sefapanosaurus, together with other transitional sauropodomorphs reported during the last decade, highlights the importance of Gondwanan taxa for understanding the palaeobiodiversity, global distribution, and macroevolutionary changes in the group related to the rise of sauropods.Facultad de Ciencias Naturales y Muse

The South African Mesozoic: advances in our understanding of the evolution, palaeobiogeography, and palaeoecology of sauropodomorph dinosaurs

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016.The Palaeontological record of South Africa is remarkable in that it preserves the two major temporal transitions of the Mesozoic: The Triassic–Jurassic boundary (the Elliot Formation) and the earliest depositional stages of the Cretaceous (the Kirkwood Formation). Work within the Elliot Formation has reiterated the importance of this horizon for our understanding of the early evolution and subsequent radiation/diversification of basal sauropodomorph dinosaurs. Moreover, inextricably contained within this radiation is the early evolution of the columnar-limbed, long necked sauropods, the largest terrestrial animals to have ever evolved. The Elliot Formation therefore imparts vital information on the genesis of the group that would become the dominant dinosaurian herbivores throughout most of the Mesozoic. However, several outstanding issues obscure a full understanding of this important radiation. Of primary concern is the complicated taxonomy of the sauropodomorphs of the Upper Triassic lower Elliot Formation and a lack of current consensus as to what precisely constitutes a true sauropod. The latter issue is further complicated by a lack of well-preserved sauropod material prior to the Toarcian. The discovery of new, associated material from both the lower and upper Elliot Formation has direct relevance to both of these concerns. Specifically, although the genus Eucnemesaurus is supported in the current analysis, the bauplan diversity of lower Elliot Sauropodomorpha remains relatively conservative save for the stocky pedal architecture of Blikanasaurus and the autapomorphically robust morphology of a newly rediscovered ilium that is potentially referable to it. Within the upper Elliot Formation, a recently discovered highly apomorphic bone-bed is diagnosed as a new species of sauropod that, in addition to placing the earliest unequivocal sauropods within the basal rocks of the Jurassic, suggests the underlying ecological factors driving the divergence of the derived sauropodan bauplan. In addition to new information provided by the Elliot Formation, two decades’ worth of collecting from the Early Cretaceous Kirkwood Formation affords a long overdue insight into the sauropod fauna occupying southern Gondwana at the outset of the Cretaceous. The surprising diversity of forms recognized from the Kirkwood suggests that the taxonomic decline of Sauropoda previously inferred for the earliest Cretaceous is a product of sampling bias compounded by a generally poor fossil record. However, a lack of absolute dates for the Kirkwood Formation means that the plethora of “Jurassic-type” specimens is potentially explicable via their being contemporaneous with similar Late Jurassic faunas of eastern Africa and North America.LG201

Derivation, simulation and validation of poroelastic models in dental biomechanics

Poroelasticity and mechanics of growth are playing an increasingly relevant role in biomechanics. This work is a self- contained and holistic presentation of the modeling and simulation of non-linear poroelasticity with and without growth inhomogeneities. Balance laws of poroelasticity are derived in Cartesian coordinates. These allow to write the governing equations in a form that is general but also readily implementable. Closure relations are formally derived from the study of dissipation. We propose an approximation scheme for the poroelasticity problem based on an implicit Euler method for the time discretization and a finite element method for the spatial discretization. The non-linear system is solved by means of Newton's method. Time integration of the growth tensor is discussed for the specific case in which the rate of inelastic deformations is prescribed. We discuss the stability of the mixed finite element discretization of the arising saddle-point problem. We show that a linear finite element approximation of both the unknowns, that is not LBB compliant for the elasticity problem, is nevertheless stable when applied to the linearized poroelasticity problem. This choice enables a fast assembling phase. The discretization of the poroelastic system may present unphysical oscillations if the spatial and temporal step-sizes are not properly chosen. We study the source of these wiggles by comparing the pressure Schur complement to a reaction- diffusion problem. From our analysis, we define a novel Péclet number for the poroelastic system and we show how it depends on the shear and bulk moduli of the solid phase. This number allows to introduce a stability condition that ensures that the solution is free of unphysical oscillations. If this condition on the Péclet number is not met, we introduce a fluid pressure Laplacian stabilization in order to remove the wiggles. This stabilization technique depends on a numerical parameter, whose optimal value is given by the derived Péclet number. Finally, we propose a coupled elastic-poroelastic model for the simulation of a tooth-periodontal ligament system. Because of the high resolution required by this system, we develop an efficient multigrid Newton's method for the non-linear poroelasticity system. The stability condition has again a significant influence on the performances of this solver. If the condition on the Péclet number is not satisfied on all levels of the multigrid algorithm, poor convergence rates or even divergence of the solver can be observed. The stabilization of the coarse grid operators with the optimal fluid pressure Laplacian method is a simple and efficient method to improve the convergence rate of the multigrid solver applied to this saddle-point system. We validate our coupled model against experimental measurements realized by the group of Prof. Bourauel at the University of Bonn

Bortolin site, a new fossiliferous locality in the triassic (Ladinian/carnian) of southern brazil

A new fossiliferous site from the Pinheiros-Chiniquá Sequence (Santa Maria Supersequence) with typical tetrapod components of the Dinodontosaurus Assemblage Zone (AZ) is here described. The new site is included in the Faxinal do Soturno Structural Block. The fossil content is characterized by cranial and postcranial material of rauisuchian archosaurs, traversodontid and chiniquodontid cynodonts and dicynodonts, the first occurrence of a large-sized coelacanth fish in the Brazilian Triassic, as well as ichnological material, represented by coprolites. The presence of Luangwa together with Massetognathus raises interesting questions regarding the age of this site included in the Dinodontosaurus AZ when compared with other localities of Southern Brazil, western Argentina and Africa. As in other localities of this AZ, the fossil specimens recovered in Bortolin site exhibit remarkable differences on their fossil preservation: those from the lower portion of the outcrop (distal floodplain) possess a heterogeneous preservation (variable between poor to fairly good) whereas those from the top levels (proximal floodplain) are comparatively better preserved. This new locality, with a large amount of stratigraphically controlled fossils, constitutes a key-locality to study the distribution of Triassic terrestrial tetrapods and to perform comparisons with other sites of this AZ, in which several historical records lack a precise provenance.– Um novo sítio fossilífero é descrito para a Sequência Pinheiros-Chiniquá (Supersequência Santa Maria) com tetrápodes típicos da Zona de Associação (ZA) de Dinodontosaurus. Este novo sítio está incluído no Bloco Estrutural Faxinal do Soturno. O conteúdo fóssil é caracterizado por materiais cranianos e pós-cranianos de arcossauros rauissuquídeos, cinodontes chiniquodontídeos e traversodontídeos e dicinodontes, a primeira ocorrência de um peixe celacanto de grande tamanho, além de materiais icnológicos, representados por coprólitos. A presença de Luangwa juntamente com Massetognathus levanta interessantes questões acerca da idade desse sítio, incluído na ZA de Dinodontosaurus, quando comparado com outras localidades do sul do Brasil, oeste da Argentina e África. Assim como em outras localidades desta ZA, os espécimes fósseis coletados no sítio Bortolin apresentam diferenças notáveis na preservação dos fósseis: fósseis do nível inferior do afloramento (planície de inundação distal) apresentam preservação heterogênea (variando entre pobre a razoavelmente bem preservado) enquanto que nos níveis superiores (planície de inundação proximal), o registro fóssil é comparativamente melhor preservado. Esta nova localidade, com uma grande quantidade de fósseis estratigraficamente controlados, constitui uma localidade chave para o estudo da distribuição dos tetrápodes terrestres do Triássico e sua comparação com outros sítios desta ZA, na qual vários registros históricos carecem de uma proveniência precisa.Fil: Branco Pavanatto, Ane Elise. Universidade Federal de Santa Maria; BrasilFil: Stock Da Rosa, Átila Augusto. Universidade Federal de Santa Maria; BrasilFil: Temp Müller, Rodrigo. Universidade Federal de Santa Maria; BrasilFil: Roberto Da Silva, Lucio. Universidade Federal de Santa Maria; BrasilFil: Ribeiro, Ana Maria. Museu de Ciências Naturais do Rio Grande do Sul; BrasilFil: Martinelli, Agustín Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Dias Da Silva, Sergio. Universidade Federal de Santa Maria; Brasi