Description logics (DLs) are knowledge representation languages that provide the theoretical underpinning for modern ontology languages such as OWL and serve as the basis for the development of ontology reasoners and tools. Most modern ontology reasoners are based on optimized tableau algorithms, which perform reasoning by trying to build counter-models. More recently, another kind of reasoning algorithms has been introduced that, instead of building counter-models, directly derive logical consequences of axioms in the ontology using inference rules. Such consequence-based algorithms were first introduced for the EL family of DLs, and later extended to more expressive Horn DLs. However, up until now, consequence-based algorithms could not handle non-Horn features such as disjunctions. We consider several complementary aspects of consequence-based reasoning in this thesis. Firstly, we describe the parallelized consequence-based reasoner ELK, which is currently the fastest reasoner for EL ontologies. Secondly, we demonstrate how consequence-based algorithms can be extended to handle disjunctions using inference rules reminiscent of ordered resolution. Finally, we combine our consequence-based framework with methods based on tree decompositions, and thus obtain what we believe are the first fixed-parameter tractability results for subsumption reasoning in DLs.

La symétrie est par définition un concept multidisciplinaire. Il apparaît dans de nombreux domaines. En général, elle revient à une transformation qui laisse invariant un objet. Le problème de satisfaisabilité (SAT) occupe un rôle central en théorie de la complexité. Il est le problème de décision de référence de la classe NP-complet (Cook, 71). Il consiste à déterminer si une formule CNF admet ou non une valuation qui la rend vraie. Dans la première contribution de ce mémoire, nous avons introduit une nouvelle méthode complète qui élimine toutes les symétries locales pour la résolution du problème SAT en exploitant son groupe des symétries. Les résultats obtenus montrent que l'exploitation des symétries locales est meilleure que l'exploitation des symétries globales sur certaines instances SAT et que les deux types de symétries sont complémentaires, leur combinaison donne une meilleure exploitation.En deuxième contribution, nous proposons une approche d'apprentissage de clauses pour les solveurs SAT modernes en utilisant les symétries. Cette méthode n'élimine pas les modèles symétriques comme font les méthodes statiques d'élimination des symétries. Elle évite d'explorer des sous-espaces correspondant aux no-goods symétriques de l'interprétation partielle courante. Les résultats obtenus montrent que l'utilisation de ces symétries et ce nouveau schéma d'apprentissage est profitable pour les solveurs CDCL.En Intelligence Artificielle, on inclut souvent la non-monotonie et l'incertitude dans le raisonnement sur les connaissances avec exceptions. Pour cela, en troisième et dernière contribution, nous avons étendu la notion de symétrie à des logiques non classiques (non-monotones) telles que les logiques préférentielles, les X-logiques et les logiques des défauts.Nous avons montré comment raisonner par symétrie dans ces logiques et nous avons mis en évidence l'existence de certaines symétries dans ces logiques qui n'existent pas dans les logiques classiques. / Symmetry is by definition a multidisciplinary concept. It appears in many fields. In general, it is a transformation which leaves an object invariant. The problem of satisfiability (SAT) is one of the central problems in the complexity theory. It is the first decision Np-complete problem (Cook, 71). It deals with determining if a CNF formula admits a valuation which makes it true. First we introduce a new method which eliminates all the local symmetries during the resolution of a SAT problem by exploiting its group of symmetries. Our experimental results show that for some SAT instances, exploiting local symmetries is better than exploiting just global symmetries and both types of symmetries are complementary. As a second contribution, we propose a new approach of Conflict-Driven Clause Learning based on symmetry. This method does not eliminate the symmetrical models as the static symmetry elimination methods do. It avoids exploring sub-spaces corresponding to symmetrical No-goods of the current partial interpretation. Our experimental results show that using symmetries in clause learning is advantageous for CDCL solvers.In artificial intelligence, we usually include non-monotony and uncertainty in the reasoning on knowledge with exceptions. Finally, we extended the concept of symmetry to non-classical logics that are preferential logics, X-logics and default logics. We showed how to reason by symmetry in these logics and we prove the existence of some symmetries in these non-classical logics which do not exist in classical logics.

This thesis is concerned with extending properties of regular word languages to richer structures. We consider intricate properties like the relationship between one-way and two-way temporal logics, minimization of automata, and the ability to effectively characterize logics. We investigate whether these properties can be extended to tree languages or word languages over an infinite alphabet. It is known that linear temporal logic (LTL) is as expressive as first-order logic over finite words [Kam68, GPSS80]. LTL is a unidirectional logic, that can only navigate forwards in a word, hence it is quite surprising that it can capture all of first-order logic. In fact, one of the main ideas of the proof of [GPSS80] is to show that the expressiveness of LTL is not increased if modalities for navigating backwards are added. It is also known that an extension of bidirectional LTL to ordered trees, called Conditional XPath, is first-order complete [Mar04]. We investigate whether the unidirectional fragment of Conditional XPath is also first-order complete. We show that this is not the case. In fact we show that there is a strict hierarchy of expressiveness consisting of languages that are all weaker than first-order logic. Unidirectional Conditional XPath is contained in the lowest level of this hierarchy. In the second part of the thesis we consider data word languages. That is, word languages over an infinite alphabet. We extend the theorem of Myhill and Nerode to a class of automata for data word languages, called deterministic finite memory automata (DMA). We give a characterization of the languages that are accepted by DMA, and also provide an algorithm for minimizing DMA. Finally we extend theorems of Büchi, Schützenberger, McNaughton, and Papert to data word languages. A theorem of Büchi states that a language is regular iff it can be defined in monadic second-order logic. Schützenberger, McNaughton, and Papert have provided an effective characterization of first-order logic, that is, an algorithm for deciding whether a regular language can be defined in first-order logic. We provide a counterpart of Büchi's theorem for data languages. More precisely we define a new logic and we show that it has the same expressiveness as non-deterministic finite memory automata. We then turn to a smaller class of data languages, those that are recognized by algebraic objects called orbit finite data monoids. We define a second new logic and show that it can define precisely the languages accepted by orbit finite data monoids. We provide an effective characterization of a first-order variant of this second logic, as well as of restrictions of first-order logic, such as its two variable fragment and local variants.

A reutilização de conhecimento é uma tarefa chave para qualquer sistema computacional. Entretanto, o reúso indiscriminado desse conhecimento pode gerar resultados conflitantes com o objetivo de uso do conhecimento, levando sistemas a se comportarem de maneira imprevisível. Neste trabalho estudamos as consequências do reúso de conhecimento em ontologias baseadas em lógicas de descrição. Focamos principalmente nos problemas que podem ser causados pela fusão de ontologias. Investigamos e comparamos a capacidade das ferramentas de desenvolvimento de ontologias atuais de lidarem com esses problemas e como a teoria se desenvolveu para resolver os mesmos problemas. Realizamos a construção de um arcabouço lógico e de software, organizado na forma de um processo, que tem como objetivo auxiliar o projetista de ontologias a resolver conflitos advindos da fusão. O processo agrupa tarefas descritas normalmente na literatura em separado. Acreditamos que a união dessas abordagens leva a uma melhor solução de conflitos. Durante o desenvolvimento deste trabalho, concentramos nossos esforços principalmente no desenvolvimento de algoritmos para a construção de sub-ontologias maximais, onde os conflitos não ocorram, bem como a ordenação desses conjuntos segundo critérios comuns discutidos na literatura. Tais estratégias foram implementadas em software e testadas utilizando dados gerados automaticamente e dados reais. / Knowledge reuse is a key task during any system development. Nevertheless, careless knowledge reuse may generate conflicting outcomes regarding the system goal, leading such systems to unpredictable behaviour. With that in mind, during this research we studied the consequences of knowledge reuse in ontologies based on description logics. We focused mainly on conflicts arising from ontology merging. We investigated and compared the features developed for this purpose on ontology development tools and how the theory field proposed to deal with the same issues. We developed both a logical and a software framework grouped into a process that aims to help the ontology designer solve conflicts arising from ontology merging. The process groups common tasks that are normally described separately. We believe that the unification of these approaches should result in a better solution for the merging conflicts. We concentrated our efforts during this work on building algorithms for building maximal sub-ontologies where such conflicts are non-existent as well as means for ordering such sets according to a few relevance criteria commonly described at the literature. Such algorithms were implemented and tested against automatically generated and real data.

Orientador: Hércules de Araújo Feitosa / Banca: Edélcio Gonçalves de Souza / Banca: Mauri Cunha do Nascimento / Resumo: Dentre as diversas lógicas não-clássicas, que complementam o cálculo de predicados de primeira ordem, destacamos as lógicas moduladas. As lógicas moduladas são caracterizadas pela inclusão de um novo quantificador, chamado modulado, que tem a incumbência de interpretar aspectos indutivos de quantificadores das linguagens naturais. Como um caso particular de lógica modulada, a lógica do muito formaliza a noção intuitiva de "muitos". O quantificador do muito é representado por G. Assim, uma sentença do tipo Gxα(x) deve ser entendida como "muitos indivíduos satisfazem a propriedade α". Semanticamente, a noção de muitos está associada a uma estrutura matemática denominada família fechada superiormente e própria. Seja E um conjunto não vazio. Uma família própria fechada superiormente F em E é tal que: (i) F ⊆ P(E); (ii) E ∈ F; (iii) ∅ ∉ F; (iv) A ∈ F e A ⊆ B ⇒ B ∈ F. Intuitivamente, F caracteriza os conjuntos que possuem 'muitos' elementos. E, assim, o universo E possui muitos elementos; o ∅ não possui muitos elementos; e se A possui muitos elementos, então todo conjunto que contém A também possui muitos elementos. Com elementos sintáticos que caracterizam linguisticamente estas propriedades de F, pode-se verificar que a lógica do muito é correta e completa para uma estrutura de primeira ordem estendida por uma família própria fechada superiormente. A lógica do muito foi originalmente introduzida em um sistema dedutivo hilbertiano, baseado apenas em axiomas e regras de dedução. Neste trabalho, desenvolvemos um outro sistema dedutivo para a lógica do muito, porém num sistema de tablôs. Demonstramos, naturalmente, que esse novo sistema é equivalente ao sistema axiomático original. / Abstract: Among the several non classical logics that complement the classical first-order logic, we detach the Modulated Logics. This class of logics is characterized by extending the classical logic by the introduction of a new generalized quantifier, called modulated quantifier, that has the attribution of interpreting some inductive aspects of quantifiers in any natural language. As a particular case of Modulated Logic, the Logic of Many formalize the intuitive notion of "many". The quantifier of many is represented by G. Thus, a sentence of the type Gxα(x) must be understood like "many individuals satisfy the property α". Semantically, the notion of many is associated with a mathematical structure named proper superiorly closed family. Let E be a non empty set. A proper superiorly closed family F in E is such that: (i) F ⊆ P(E); (ii) E ∈ F; (iii) ∅ ∉ F; (iv) A ∈ F e A ⊆ B ⇒ B ∈ F. Intuitively, F characterizes the sets which have "many" elements. The empty set ∅ does not have many elements. And if A has many elements, then any set which contains A, also has many elements. The logic of many has syntactical elements that caracterize linguisticaly these properties of F. We can verify that the Logic of Many is correct and complete for a first order structure extended by a proper superiorly closed family. The Logic of Many was originally introduced in a Hilbertian deductive system, based only on axioms and rules. In this work, we developed another deductive system for the Logic of Many, but in a tableaux system. We proof that this new system is equivalent to the original one. / Mestre

The Health and Social Care Act 2012 (HSCA12) represents one of the more dramatic reforms in the history of the English National Health Service (NHS) in terms of scope and pace. The flagship of the policy was the replacement of Primary Care Trusts with Clinical Commissioning Groups (CCGs): General Practitioner (GP) led “membership organisations” with responsibility for planning and purchasing most NHS care. A new “arm’s length” body, NHS England (NHSE), was created to authorise and oversee CCGs. The purpose of this research was to critically explore the ideational content of the HSCA12 and consider it in relation to social practices at the organisational level of a CCG: to provide a detailed, contextualised account of a CCG’s early operation, paying particular attention to the implications of its officially intended status as a membership organisation. By problematising the HSCA12, I have highlighted how CCGs and the GPs that constituted them were presented as an emancipatory force saving the NHS from ineffectual managers that lacked clinical and local knowledge about what patients needed; membership organisation status was bound up with this claim of local representation, and the policy attempted to orchestrate engagement from GPs as members through normative devices and governance systems including legislation and assessment programmes. However, the policy elided the difference between GPs as individuals and GP practices and left ambiguous precisely who or what constituted a member. Thirteen months of fieldwork using ethnographic methods (meeting observations, interviews, documentary analysis) were carried out with a case CCG: Notchcroft. The policy delineated “the membership” and “the governing body” as sub-groups within the CCG, but I found many others were involved in CCG governance processes and created “the governing core” concept to describe them. Confusion in the policy over exactly who was a member was paralleled in the CCG. The governing core, many of whom were GPs, were involved in performance assessment processes of GPs in order to fulfil a legal obligation to NHSE. This represented a further redrawing of the GP/state relationship and was a source of identity dissonance. The governing core also actively transmitted national policy norms about what it meant to be a member to the broader membership. By trying to “sell” CCG membership and encourage engagement they were attempting to legitimate the organisation and their roles within it. Notchcroft CCG’s unusual structure, with two levels (districts and locales) below central committees, appeared inefficient. This structure developed as a response to previous national commissioning policies. The institutional logics approach—employed as an analytical lens—proved useful in explaining its endurance: districts were containers for identity and interests to be protected, whilst locales were established and maintained as local “self help” organisations to support quality improvement. The initial purposes of districts and locales thus represented different logics of action that appeared self-evident to those involved, although they were less obvious to an external observer. In time, these initial logics were eroded, and districts and locales were given additional functions. These findings illustrate the emergent tension between national policy and local enactment, and demonstrate how local socio-historical context plays an important role in shaping how policy is realised in practice.

Este trabalho apresenta três principais contribuições: i. a proposta de uma nova lógica de descrição probabilística; ii. um novo algoritmo de inferência em primeira ordem a ser utilizado em terminologias representadas nessa lógica; e iii. aplicações práticas em problemas reais. A lógica aqui proposta, crALC (credal ALC), adiciona inclusões probabilísticas na popular lógica ALC combinando as terminologias com condições de aciclicidade, de Markov, e adotando uma semântica baseada em interpretações. Como os métodos de inferência exata tradicionalmente apresentam problemas de escalabilidade devido à presença de quantificadores (restrições universal e existencial), apresentamos um algoritmo de loopy propagation em primeira-ordem que se comporta bem para terminologias com domínios não triviais. Uma série de testes foi feita com o algoritmo proposto em comparação com algoritmos tradicionais da literatura; os resultados apresentados mostram uma clara vantagem em relação aos outros algoritmos. São apresentadas ainda duas aplicações da lógica e do algoritmo para resolver problemas reais da área de robótica móvel. Embora os problemas tratados sejam relativamente simples, eles constituem a base de muitos outros problemas da área, sendo um passo importante na representação de conhecimento de agentes/robôs autônomos e no raciocínio sobre esse conhecimento. / This work presents two major contributions: i. a new probabilistic description logic; ii. a new algorithm for inference in terminologies expressed in this logic; iii. practical applications in real tasks. The proposed logic, referred to as crALC (credal ALC), adds probabilistic inclusions to the popular logic ALC, combining the usual acyclicity and Markov conditions, and adopting interpretation-based semantics. As exact inference does not seem scalable due to the presence of quantifiers (existential and universal), we present a first-order loopy propagation algorithm that behaves appropriately for non-trivial domain sizes. A series of tests were done comparing the performance of the proposed algorithm against traditional ones; the presented results are favorable to the first-order algorithm. Two applications in the field of mobile robotics are presented, using the new probabilistic logic and the inference algorithm. Though the problems can be considered simple, they constitute the basis for many other tasks in mobile robotics, being a important step in knowledge representation and in reasoning about it.

There has been a great deal of research conducted which examines the development of student-athletes on college campuses. However, there has been limited investigation into how the institutional logics (i.e. the belief structures and related practices) within an athletic department may affect the manner in which athletic administrators and coaches perceive and approach the development of their student-athletes. The purpose of this study was to understand the institutional logics of an NCAA Division II athletic department and how those logics may affect student-athletes. In order to address the purpose and research questions of this study, I conducted a qualitative case study at a private university where I interviewed thirteen members of the university including eight members of the athletic department and five university faculty members and administrators. Additional data were obtained through various documents such as the university's mission statement and the NCAA Division II Handbook. It was found that the athletic department operates under certain institutional logics wherein they are expected to foster student-athlete development. These include the academic, physical, social, and spiritual aspects of their development. Additionally, the athletic department is expected to enhance the university by building community and promoting the mission and vision of the university. Finally, winning athletic competitions is an important expectation of members of the athletic department. Further exploration of the data reveals that certain aspects of these logics may conflict. Primarily, the participants acknowledged that they were expected to foster the development of their athletes in other aspects beyond athletics; yet their primary job performance evaluations were based on wins and losses. Additionally, the logic of enhancing the university may also contend with the academic development of the student-athletes. This is significant because research has suggested that conflicting institutional logics within an organization may lead to confusion as to which logics are paramount. Though the specific findings of this research may be contextually bound, this provides insight into how the institutional logics of an organization may influence the actions of its members and key stakeholders who are influenced by the processes within that organization.

No description available.

We consider the overlap between reasoning involved in <em>conjunctive query optimization</em> (CQO) and in tableaux-based approaches to reasoning about subsumption in <em>description logics</em> (DLs). In both cases, an underlying graph is created, searched and modified. This process is determined by a given <em>query</em> and <em>database schema</em> in the first case and by a given <em>description</em> and <em>terminology</em> in the second. The opportunities for overlap derive from an abundance of reductions of various schema languages to terminologies for common DL dialects, and from the fact that descriptions can in turn be viewed as queries that compute a single column. <br /><br /> Our main contributions are as follows. We present the design and implementation of a common graph utility that integrates the requirements for both CQO and DL reasoning. We then verify this model by also presenting the design and implementation for two drivers, one that implements a query optimizer for a conjunctive query language extended with descriptions, and one that implements a complete DL reasoner for a feature based DL dialect.