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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Apprentissage de problèmes de contraintes / Constraint problems learning

Lopez, Matthieu 08 December 2011 (has links)
La programmation par contraintes permet de modéliser des problèmes et offre des méthodes de résolution efficaces. Cependant, sa complexité augmentant ces dernières années, son utilisation, notamment pour modéliser des problèmes, est devenue limitée à des utilisateurs possédant une bonne expérience dans le domaine. Cette thèse s’inscrit dans un cadre visant à automatiser la modélisation. Les techniques existantes ont montré des résultats encourageants mais certaines exigences rendent leur utilisation encore problématique. Dans une première partie, nous proposons de dépasser une limite existante qui réside dans la nécessité pour l’utilisateur de fournir des solutions du problème qu’il veut modéliser. En remplacement, il nous fournit des solutions de problèmes proches, c’est-à-dire de problèmes dont la sémantique de fond est la même mais dont les variables et leur domaine peuvent changer. Pour exploiter de telles données, nous proposons d’acquérir, grâce à des techniques de programmation logique inductive, un modèle plus abstrait que le réseau de contraintes. Une fois appris, ce modèle est ensuite transformé pour correspondre au problème initial que souhaitait résoudre l’utilisateur. Nous montrons également que la phase d’apprentissage se heurte à des limites pathologiques et qui nous ont contraints à développer un nouvel algorithme pour synthétiser ces modèles abstraits. Dans une seconde partie, nous nous intéressons à la possibilité pour l’utilisateur de ne pas donner d’exemples du tout. En partant d’un CSP sans aucune contrainte, notre méthode consiste à résoudre le problème de l’utilisateur de manière classique. Grâce à un arbre de recherche, nous affectons progressivement des valeurs aux variables. Quand notre outil ne peut décider si l’affectation partielle courante est correcte ou non, nous demandons à l’utilisateur de guider la recherche sous forme de requêtes. Ces requêtes permettent de trouver des contraintes à ajouter aux modèles du CSP et ainsi améliorer la recherche. / Constraint programming allows to model many kind of problems with efficient solving methods. However, its complexity has increased these last years and its use, notably to model problems, has become limited to people with a fair expertise in the domain. This thesis deals with automating the modeling task in constraint programming. Methods already exist, with encouraging results, but many requirements are debatable. In a first part, we propose to avoid the limitation consisting, for the user, in providing solutions of the problem she aims to solve. As a replacement of these solutions, the user has to provide solutions of closed problem, i.e problem with same semantic but where variables and domains can be different. To handle this kind of data, we acquire, thanks to inductive logic programming, a more abstract model than the constraint network. When this model is learned, it is translated in the very constraint network the user aims to model. We show the limitations of learning method to build such a model due to pathological problems and explain the new algorithm we have developed to build these abstract models. In a second part, we are interesting in the possibility to the user to not provide any examples. Starting with a CSP without constraints, our method consists in solving the problem the user wants in a standard way. Thanks to a search tree, we affect to each variable a value. When our tool cannot decide if the current partial affectation is correct or not, we ask to the user, with yes/no queries, to guide the search. These queries allow to find constraints to add to the model and then to improve the quality of the search.
2

Modeling Faceted Browsing with Category Theory for Reuse and Interoperability

Harris, Daniel R. 01 January 2017 (has links)
Faceted browsing (also called faceted search or faceted navigation) is an exploratory search model where facets assist in the interactive navigation of search results. Facets are attributes that have been assigned to describe resources being explored; a faceted taxonomy is a collection of facets provided by the interface and is often organized as sets, hierarchies, or graphs. Faceted browsing has become ubiquitous with modern digital libraries and online search engines, yet the process is still difficult to abstractly model in a manner that supports the development of interoperable and reusable interfaces. We propose category theory as a theoretical foundation for faceted browsing and demonstrate how the interactive process can be mathematically abstracted in order to support the development of reusable and interoperable faceted systems. Existing efforts in facet modeling are based upon set theory, formal concept analysis, and light-weight ontologies, but in many regards they are implementations of faceted browsing rather than a specification of the basic, underlying structures and interactions. We will demonstrate that category theory allows us to specify faceted objects and study the relationships and interactions within a faceted browsing system. Resulting implementations can then be constructed through a category-theoretic lens using these models, allowing abstract comparison and communication that naturally support interoperability and reuse. In this context, reuse and interoperability are at two levels: between discrete systems and within a single system. Our model works at both levels by leveraging category theory as a common language for representation and computation. We will establish facets and faceted taxonomies as categories and will demonstrate how the computational elements of category theory, including products, merges, pushouts, and pullbacks, extend the usefulness of our model. More specifically, we demonstrate that categorical constructions such as the pullback and pushout operations can help organize and reorganize facets; these operations in particular can produce faceted views containing relationships not found in the original source taxonomy. We show how our category-theoretic model of facets relates to database schemas and discuss how this relationship assists in implementing the abstractions presented. We give examples of interactive interfaces from the biomedical domain to help illustrate how our abstractions relate to real-world requirements while enabling systematic reuse and interoperability. We introduce DELVE (Document ExpLoration and Visualization Engine), our framework for developing interactive visualizations as modular Web-applications in order to assist researchers with exploratory literature search. We show how facets relate to and control visualizations; we give three examples of text visualizations that either contain or interact with facets. We show how each of these visualizations can be represented with our model and demonstrate how our model directly informs implementation. With our general framework for communicating consistently about facets at a high level of abstraction, we enable the construction of interoperable interfaces and enable the intelligent reuse of both existing and future efforts.

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