L'objectif du problème appelé "Ontology-based data access" (OBDA) est d'améliorer la réponse à des requêtes en prenant en compte des connaissances d'ordre général durant l'évaluation des requêtes. Ces connaissances générales sont représentées à l'aide d'une ontologie, qui est exprimée dans cette thèse grâce à des formules logiques du premier ordre, appelées règles existentielles, et aussi connues sous le nom de "tuple-generating dependencies" et Datalog+/-. L'expressivité des formules utilisées est telle que l'évaluation de requêtes devient un problème indécidable, et cela a conduit la communauté à définir de nombreux cas décidables, c'est-à-dire des restrictions sur les ensembles de règles existentielles considérés. La contribution de cette thèse est double : tout d'abord, nous proposons une vue unifiée sur une grande fraction des cas décidables connus, et fournissons par là même une analyse de complexité et un algorithme optimal dans le pire des cas. Nous considérons également l'approche couramment utilisée de réécriture de requêtes, et proposons un algorithme générique qui permet de surmonter certaines causes évidentes d'explosion combinatoire qui rendent les approches classiques pratiquement inapplicables. / Ontology-based data access (OBDA) aims at enriching query answering by taking general background knowledge into account when evaluating queries. This background knowledge is represented by means of an ontology, that is expressed in this thesis by a very expressive class of first-order formulas, called existential rules (sometimes also tuple-generating dependencies and Datalog+/-). The high expressivity of the used formalism results in the undecidability of query answering, and numerous decidable classes (that is, restrictions on the sets of existential rules) have been proposed in the literature. The contribution of this thesis is two-fold: first, we propose a unified view of a large part of these classes, together with a complexity analysis and a worst-case optimal algorithm for the introduced generic class. Second, we consider the popular approach of query rewriting, and propose a generic algorithm that overcomes trivial causes of combinatorial explosion that make classical approaches inapplicable.

In this thesis we will introduce multioperator weighted monadic datalog (mwmd), a formal model for specifying tree series, tree transformations, and tree languages. This model combines aspects of multioperator weighted tree automata (wmta), weighted monadic datalog (wmd), and monadic datalog tree transducers (mdtt). In order to develop a rich theory we will define multiple versions of semantics for mwmd and compare their expressiveness. We will study normal forms and decidability results of mwmd and show (by employing particular semantic domains) that the theory of mwmd subsumes the theory of both wmd and mdtt. We conclude this thesis by showing that mwmd even contain wmta as a syntactic subclass and present results concerning this subclass.

La masse d’information disponible sur leWeb s’accroit rapidement, sous l’afflux de données en provenance des utilisateurs et des compagnies. Ces données qu’ils souhaitent partager de façon controllée sur le réseau et quisont réparties sur de nombreuses machines et systèmes différents, ne sont rapidement plus gérables directement par des moyens humains. Nous introduisons WebdamExchange, un nouveau modèle de bases de connaissancesdistribuées, qui comprend des assertions au sujet des données, du contrôle d’accés et de la distribution. Ces assertions peuvent être échangées avec d’autres pairs, répliquées, interrogées et mises à jour, en gardant la trace de leur origine. La base de connaissance permet aussi de guider de façon automatique sa propre gestion. WebdamExchange est basé surWebdamLog, un nouveau langage de règles pour la gestion de données distribuées, qui associe formellement les règles déductives de Datalog avec négation et les règles actives de Datalog::. WebdamLog met l’accent sur la dynamicité et les interactions, caractéristiques du Web 2.0. Ce modèle procure à la fois un langage expressif pour la spécification de systèmes distribués complexes et un cadre formel pour l’étude de propriétés fondamentales de la distribution. Nous présentons aussi une implémentation de notre base de connaissance. Nous pensons que ces contributions formentune fondation solide pour surmonter les problèmes de gestion de données du Web, en particulier dans le cadre du contrôle d’accès. / The amount of information on the Web is spreading very rapidly. Users as well as companies bring data to the network and are willing to share with others. They quickly reach a situation where their information is hosted on many machines they own and on a large number of autonomous systems where they have accounts. Management of all this information is rapidly becoming beyond human expertise. We introduce WebdamExchange, a novel distributed knowledge-base model that includes logical statements for specifying information, access control, secrets, distribution, and knowledge about other peers. These statements can be communicated, replicated, queried, and updated, while keeping track of time and provenance. The resulting knowledge guides distributed data management. WebdamExchange model is based on WebdamLog, a new rule-based language for distributed data management that combines in a formal setting deductiverules as in Datalog with negation, (to specify intensional data) and active rules as in Datalog:: (for updates and communications). The model provides a novel setting with a strong emphasis on dynamicity and interactions(in a Web 2.0 style). Because the model is powerful, it provides a clean basis for the specification of complex distributed applications. Because it is simple, it provides a formal framework for studying many facets of the problem such as distribution, concurrency, and expressivity in the context of distributed autonomous peers. We also discuss an implementation of a proof-of-concept system that handles all the components of the knowledge base and experiments with a lighter system designed for smartphones. We believe that these contributions are a good foundation to overcome theproblems of Web data management, in particular with respect to access control.

Les bibliothèques numériques sont des systèmes d'information complexes stockant des ressources numériques (par exemple, texte, images, sons, audio), ainsi que des informations sur les ressources numériques ou non-numériques; ces informations sont appelées des métadonnées. Nous proposons un modèle de données pour les bibliothèques numériques permettant l'identification des ressources, l’utilisation de métadonnées et la réutilisation des ressources stockées, ainsi qu’un langage de requêtes pour l’interrogation de ressources. Le modèle que nous proposons est inspiré par l'architecture du Web, qui forme une base solide et universellement acceptée pour les notions et les services attendus d'une bibliothèque numérique. Nous formalisons notre modèle comme une théorie du premier ordre, afin d’exprimer les concepts de bases de la bibliothèque numérique, sans aucune contrainte technique. Les axiomes de la théorie donnent la sémantique formelle des notions du modèle, et en même temps fournissent une définition de la connaissance qui est implicite dans une bibliothèque numérique. La théorie est traduite en un programme Datalog qui, étant donnée une bibliothèque numérique, permet de la compléter efficacement avec les connaissances implicites. Le but de notre travail est de contribuer à la technologie de gestion des informations des bibliothèques numériques. De cette façon, nous pouvons montrer la faisabilité théorique de notre modèle, en montrant qu'il peut être efficacement appliqué. En outre, nous démontrons la faisabilité pratique du modèle en fournissant une traduction complète du modèle en RDF et du langage de requêtes en SPARQL.Nous fournissons un calcul sain et complet pour raisonner sur les graphes RDF résultant de la traduction. Selon ce calcul, nous prouvons la correction de ces deux traductions, montrant que les fonctions de traduction préservent la sémantique de la bibliothèque numérique et de son langage de requêtes. / Digital Libraries are complex information systems, storing digital resources (e.g., text, images, sound, audio), as well as knowledge about digital or non-digital resources; this knowledge is referred to as metadata. We propose a data model for digital libraries supporting resource identification, use of metadata and re-use of stored resources, as well as a query language supporting discovery of resources. The model that we propose is inspired by the architecture of the Web, which forms a solid, universally accepted basis for the notions and services expected from a digital library. We formalize our model as a first-order theory, in order to be able to express the basic concepts of digital libraries without being constrained by any technical considerations. The axioms of the theory give the formal semantics of the notions of the model, and at the same time, provide a definition of the knowledge that is implicit in a digital library. The theory is then translated into a Datalog program that, given a digital library, allows to efficiently complete the digital library with the knowledge implicit in it. The goal of our research is to contribute to the information management technology of digital libraries. In this way, we are able to demonstrate the theoretical feasibility of our digital library model, by showing that it can be efficiently implemented. Moreover, we demonstrate our model’s practical feasibility by providing a full translation of the model into RDF and of the query language into SPARQL. We provide a sound and complete calculus for reasoning on the RDF graphs resulting from translation. Based on this calculus, we prove the correctness of both translations, showing that the translation functions preserve the semantics of the digital library and of the query language.

Die vorliegende Dissertation beinhaltet eine umfassende Untersuchung der Entscheidbarkeit und Komplexität der Probleme, die sich durch eine statische Analyse von monadischem Datalog auf endlichen gefärbten Bäumen stellen. Statische Analyse bedeutet hierbei Anfrageoptimierung ohne Blick auf konkrete Instanzen, aber mit Rücksicht auf deren zugrunde liegende Struktur. Im Kern beinhaltet dies die Lösung der drei folgenden Probleme: das Leerheitsproblem (die Frage, ob eine Anfrage auf jeder Instanz ein leeres Ergebnis liefert), das Äquivalenzproblem (die Frage, ob zwei Anfragen auf jeder Instanz das gleiche Ergebnis liefern) und das Query-Containment-Problem (die Frage, ob das Ergebnis der einen Anfrage auf jeder Datenbank im Ergebnis der anderen Anfrage enthalten ist). Von Interesse ist dabei, ob die Fragen für eine gegebene Anfragesprache entscheidbar sind und wenn ja, welche Komplexität ihnen innewohnt. Wir betrachten diese Probleme für monadisches Datalog auf unterschiedlichen Repräsentationen für endliche gefärbte Bäume. Hierbei unterscheiden wir zwischen ungeordneten und geordneten Bäumen, welche die Achsen child bzw. firstchild und nextsibling und deren Erweiterung um die descendant-Achse nutzen. Außerdem unterscheiden wir Alphabete mit und ohne Rang. Monadisches Datalog ist eine Anfragesprache, die in Abhängigkeit vom gewählten Schema die Ausdrucksstärke der monadischen Logik zweiter Stufe (MSO) erreicht und dennoch effizient ausgewertet werden kann. Wir zeigen, dass unter in der Datenbanktheorie üblichen Mengensemantik die drei genannten Probleme für alle Schemata ohne descendant-Achse EXPTIME-vollständig sind und lösbar in 2EXPTIME, falls die descendant-Achse involviert ist. Eine passende untere Schranke wird für fast alle Schemata gezeigt. Unter Multimengensemantik lassen sich die obigen Ergebnisse für das Leerheitsproblem übertragen, während das Query-Containment-Problem für alle betrachteten Schemata unentscheidbar ist. / This thesis provides a comprehensive investigation into the decidability and complexity of the fundamental problems entailed by static analysis of monadic datalog on finite labeled trees. Static analysis is used for optimizing queries without considering concrete database instances but exploiting information about the represented structure. Static analysis relies on three basic decision problems. First, the emptiness problem, whose task is to decide whether a query returns the empty result on every database. Second, the equivalence problem asking if the result of two given queries always coincides on every database. And finally, the query containment problem where it is to decide whether on every database a given query produces a subset of the results of a second given query. We are interested in finding out whether these problems are decidable and, if so, what their complexity is. We consider the aforementioned problems for monadic datalog on different representations of finite labeled trees. We distinguish unordered and ordered trees which use the axis child, as well as the axes firstchild and nextsibling, respectively. An extension of the schemas by the descendant-axis is also considered. Furthermore, we distinguish ranked and unranked labeling alphabets. Depending on the schema, the query language monadic datalog can reach the expressive power of monadic second order logic but remains efficiently evaluable. Under set semantics, we show EXPTIME-completness for all used schemas where the descendant-axis is omitted. If the descendant-axis is involved, we present an algorithm that solves the problem within 2-fold exponential time. A matching lower bound is proven for virtually all schemas. Finally, we prove that the complexity of the emptiness problem of monadic datalog on finite trees under bag semantics is the same as under set semantics. Furthermore, we show that the query containment problem of monadic datalog under bag semantics is undecidable in general.

Les grammaires catégorielles abstraites (ou λ-grammaires) sont un formalisme basé sur le λ-calcul simplement typé. Elles peuvent être vues comme des grammaires générant de tels termes, et ont été introduites afin de modéliser l’interface entre la syntaxe et la sémantique du langage naturel, réunissant deux idées fondamentales : la distinction entre tectogrammaire (c.a.d. structure profonde d’un énoncé) et phénogrammaire (c.a.d représentation de la surface d’un énoncé) de la langue, ex- primé par Curry ; et une modélisation algébrique du principe de compositionnalité afin de rendre compte de la sémantique des phrases, due à Montague. Un des avantages principaux de ce formalisme est que l’analyse d’une grammaires catégorielle abstraite permet de résoudre aussi bien le problème de l’analyse de texte, que celui de la génération de texte. Des algorithmes d’analyse efficaces ont été découverts pour les grammaires catégorielles abstraites de termes linéaires et quasi-linéaires, alors que le problème de l’analyse est non-élémentaire dans sa forme la plus générale. Nous proposons d’étudier des classes de termes pour lesquels l’analyse grammaticale reste solvable en temps polynomial. Ces résultats s’appuient principalement sur deux théorèmes de typage : le théorème de cohérence, spécifiant qu’un λ-terme donné est l’unique habitant d’un certain typage ; et le théorème d’expansion du sujet, spécifiant que deux termes β-équivalents habitent les même typages. Afin de mener cette étude à bien, nous utiliserons une représentation abstraite des notions de λ-termes et de typages, sous forme de jeux. En particulier, nous nous appuierons grandement sur cette notion afin de démontrer le théorème de cohérence pour de nouvelles familles de λ-termes et de typages. Grâce à ces résultats, nous montrerons qu’il est possible de construire de manière directe, un reconnaisseur dans le langage Datalog, pour des grammaires catégorielles abstraites de -termes quasi-affines. / Abstract categorial grammars (or, equivalently, lambda-grammars) is formalism based on the simply-typed lambda-calculus. These grammars can be described as grammars of such terms and were introduced in order to bring a model of the syntax-semantics interface in natural language, based on two main ideas: the distinction between the tectogrammatical (i.e. the deep structure of an utterance) and phenogrammatical (i.e. the interpretation of this structure) levels in natural languages, which was expressed by Curry; and an algebraic modeling of the principle of compositionality in order to give account of the semantics of a sentence. an idea formalized by Montague. One of the main advantages of abstract categorial grammars is that both the problems of natural language parsing and generation can be tackled under the same problem: parsing abstract categorial grammars. Efficient algorithms were discovered for abstract categorial grammars of linear and almost linear lambda-terms, while it is known the recognition problem is decidable but non-elementary in general. This work focuses on the study of classes of terms for which parsing can still be solved in polynomial time. The results we give are mainly based on two theorems: the coherence theorem which specifies that a given lambda-term in the desired class must be the unique inhabitant of one of its typing; and the subject expansion theorem, which states that two beta-equivalent terms of the desired class must inhabit the same typings. In order to lead the study, we use an alternative representation of both simply-typed lambda-terms and their typings as games. In particular, we will use this representation in order to prove the coherence theorems for new classes of lambda-terms. Thanks to these results, we will show it is possible to build in a direct way, recognizers for grammars of almost affine lambda-terms as Datalog programs.

In this thesis we will introduce multioperator weighted monadic datalog (mwmd), a formal model for specifying tree series, tree transformations, and tree languages. This model combines aspects of multioperator weighted tree automata (wmta), weighted monadic datalog (wmd), and monadic datalog tree transducers (mdtt). In order to develop a rich theory we will define multiple versions of semantics for mwmd and compare their expressiveness. We will study normal forms and decidability results of mwmd and show (by employing particular semantic domains) that the theory of mwmd subsumes the theory of both wmd and mdtt. We conclude this thesis by showing that mwmd even contain wmta as a syntactic subclass and present results concerning this subclass.

The amount of information on the Web is spreading very rapidly. Users as well as companies bring data to the network and are willing to share with others. They quickly reach a situation where their information is hosted on many machines they own and on a large number of autonomous systems where they have accounts. Management of all this information is rapidly becoming beyond human expertise. We introduce WebdamExchange, a novel distributed knowledge-base model that includes logical statements for specifying information, access control, secrets, distribution, and knowledge about other peers. These statements can be communicated, replicated, queried, and updated, while keeping track of time and provenance. The resulting knowledge guides distributed data management. WebdamExchange model is based on WebdamLog, a new rule-based language for distributed data management that combines in a formal setting deductiverules as in Datalog with negation, (to specify intensional data) and active rules as in Datalog:: (for updates and communications). The model provides a novel setting with a strong emphasis on dynamicity and interactions(in a Web 2.0 style). Because the model is powerful, it provides a clean basis for the specification of complex distributed applications. Because it is simple, it provides a formal framework for studying many facets of the problem such as distribution, concurrency, and expressivity in the context of distributed autonomous peers. We also discuss an implementation of a proof-of-concept system that handles all the components of the knowledge base and experiments with a lighter system designed for smartphones. We believe that these contributions are a good foundation to overcome theproblems of Web data management, in particular with respect to access control.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Este trabalho apresenta o desenvolvimento e avaliaÃÃo de um sistema de monitoramento com tecnologia Java e Bluetooth para o auxilio no gerenciamento da condiÃÃo de transformadores de distribuiÃÃo a partir de modelos tÃrmicos. Sabe-se que monitorar a condiÃÃo dos transformadores tem sido objeto de preocupaÃÃo no que diz respeito a evitar as perdas econÃmicas causadas por falhas no equipamento e a consequente descontinuidade do serviÃo. à possÃvel, atravÃs da gestÃo do sistema: maximizar a vida Ãtil dos equipamentos monitorados; melhorar a confiabilidade da rede; reduzir os custos de manutenÃÃo. AtravÃs do levantamento bibliogrÃfico de sistemas de monitoramento atuais, de suas funcionalidades, em funÃÃo de recentes tecnologias de software e hardware, e do estudo de modelos tÃrmicos aplicados a transformadores, foi desenvolvido um sistema de coleta de dados e uma interface para anÃlise de dados. Este trabalho traz uma contribuiÃÃo para o desenvolvimento desses sistemas, propondo o uso de dispositivos mÃveis como uma estratÃgia economicamente viÃvel para coletar dados de transformadores de distribuiÃÃo, e a utilizaÃÃo dos dados coletados por estes dispositivos para gerar modelos tÃrmicos (das temperaturas do topo do Ãleo e do ponto quente) que permitam: (i) estabelecer limites mÃximos de carga para o equipamento, e (ii) estimar sua perda de vida Ãtil. Estas informaÃÃes fornecidas pelo sistema de monitoramento proposto devem servir como suporte à implementaÃÃo de planos de aÃÃo da concessionÃria de energia elÃtrica para: (i) a eventual substituiÃÃo de equipamentos, (ii) a adequaÃÃo na distribuiÃÃo das cargas, (iii) a priorizaÃÃo no caso de necessidade de atuaÃÃo do sistema de proteÃÃo. / This paper presents the development and evaluation of a monitoring system with Bluetooth and Java technology to aid managing the condition of distribution transformers through thermal models. It is well known that monitor the condition of transformers has been the subject of concern in relation to avoid economic losses caused by equipment failure. It is possible, through the system management: (i) maximize the life time of the monitored equipment, (ii) improve the reliability of the electrical grid and (iii) reduce its maintenance costs. Through a bibliographical survey of transformer condition monitoring systems and study of thermal models applied to transformers, was developed a system for data acquisition and an interface for data analysis. This work brings a contribution to the development of these systems, proposing the use of mobile devices as a viable strategy to collect data of distribution transformers and using data collected by those devices for generating thermal models (to estimate top-oil and hotspot temperature) that will let us: (i) establish maximum load for the equipment, and (ii) estimate the loss of life. The information provided by the condition monitoring system proposed should serve as support to electric utility company to implement action plans to help possible exchange of equipment, do a more balanced load in their distribution transformers and help prioritizing, in case of any necessary actuation of the system protection.

This can be considered as a multidisciplinary research where ideas from Operations Research, Data Science and Logic came together to solve an inconsistency handling problem in a special type of ontology. / High data quality is a prerequisite for accurate data analysis. However, data inconsistencies often arise in real data, leading to untrusted decision making downstream in the data analysis pipeline. In this research, we study the problem of inconsistency detection and repair of the Ontology Multi-dimensional Data Model (OMD). We propose a framework of data quality assessment, and repair for the OMD. We formally define a weight-based repair-by-deletion semantics, and present an automatic weight generation mechanism that considers multiple input criteria. Our methods are rooted in multi-criteria decision making that consider the correlation, contrast, and conflict that may exist among multiple criteria, and is often needed in the data cleaning domain. After weight generation we present a dynamic programming based Min-Sum algorithm to identify minimal weight solution. We then apply evolutionary optimization techniques and demonstrate improved performance using medical datasets, making it realizable in practice. / Thesis / Master of Computer Science (MCS) / Accurate data analysis requires high quality data as input. In this research, we study inconsistency in an ontology known as Ontology Multi-dimensional Data (OMD) Model and propose algorithms to repair them based on their automatically generated relative weights. We proposed two techniques to restore consistency, one provides optimal results but takes longer time compared to the other one, which produces sub-optimal results but fast enough for practical purposes, shown with experiments on datasets.