A Labeled Graph Kernel for Relationship Extraction

In this paper, we propose an approach for Relationship Extraction (RE) based on labeled graph kernels. The kernel we propose is a particularization of a random walk kernel that exploits two properties previously studied in the RE literature: (i) the words between the candidate entities or connecting them in a syntactic representation are particularly likely to carry information regarding the relationship; and (ii) combining information from distinct sources in a kernel may help the RE system make better decisions. We performed experiments on a dataset of protein-protein interactions and the results show that our approach obtains effectiveness values that are comparable with the state-of-the art kernel methods. Moreover, our approach is able to outperform the state-of-the-art kernels when combined with other kernel methods

Improving Product-related Patent Information Access with Automated Technology Ontology Extraction

Ph.DDOCTOR OF PHILOSOPH

Unsupervised relation extraction for e-learning applications

In this modern era many educational institutes and business organisations are adopting the e-Learning approach as it provides an effective method for educating and testing their students and staff. The continuous development in the area of information technology and increasing use of the internet has resulted in a huge global market and rapid growth for e-Learning. Multiple Choice Tests (MCTs) are a popular form of assessment and are quite frequently used by many e-Learning applications as they are well adapted to assessing factual, conceptual and procedural information. In this thesis, we present an alternative to the lengthy and time-consuming activity of developing MCTs by proposing a Natural Language Processing (NLP) based approach that relies on semantic relations extracted using Information Extraction to automatically generate MCTs. Information Extraction (IE) is an NLP field used to recognise the most important entities present in a text, and the relations between those concepts, regardless of their surface realisations. In IE, text is processed at a semantic level that allows the partial representation of the meaning of a sentence to be produced. IE has two major subtasks: Named Entity Recognition (NER) and Relation Extraction (RE). In this work, we present two unsupervised RE approaches (surface-based and dependency-based). The aim of both approaches is to identify the most important semantic relations in a document without assigning explicit labels to them in order to ensure broad coverage, unrestricted to predefined types of relations. In the surface-based approach, we examined different surface pattern types, each implementing different assumptions about the linguistic expression of semantic relations between named entities while in the dependency-based approach we explored how dependency relations based on dependency trees can be helpful in extracting relations between named entities. Our findings indicate that the presented approaches are capable of achieving high precision rates. Our experiments make use of traditional, manually compiled corpora along with similar corpora automatically collected from the Web. We found that an automatically collected web corpus is still unable to ensure the same level of topic relevance as attained in manually compiled traditional corpora. Comparison between the surface-based and the dependency-based approaches revealed that the dependency-based approach performs better. Our research enabled us to automatically generate questions regarding the important concepts present in a domain by relying on unsupervised relation extraction approaches as extracted semantic relations allow us to identify key information in a sentence. The extracted patterns (semantic relations) are then automatically transformed into questions. In the surface-based approach, questions are automatically generated from sentences matched by the extracted surface-based semantic pattern which relies on a certain set of rules. Conversely, in the dependency-based approach questions are automatically generated by traversing the dependency tree of extracted sentence matched by the dependency-based semantic patterns. The MCQ systems produced from these surface-based and dependency-based semantic patterns were extrinsically evaluated by two domain experts in terms of questions and distractors readability, usefulness of semantic relations, relevance, acceptability of questions and distractors and overall MCQ usability. The evaluation results revealed that the MCQ system based on dependency-based semantic relations performed better than the surface-based one. A major outcome of this work is an integrated system for MCQ generation that has been evaluated by potential end users.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Unsupervised Information Extraction From Text Extraction and Clustering of Relations between Entities

L'extraction d'information non supervisée en domaine ouvert est une évolution récente de l'extraction d'information adaptée à des contextes dans lesquels le besoin informationnel est faiblement spécifié. Dans ce cadre, la thèse se concentre plus particulièrement sur l'extraction et le regroupement de relations entre entités en se donnant la possibilité de traiter des volumes importants de données.L'extraction de relations se fixe plus précisément pour objectif de faire émerger des relations de type non prédéfini à partir de textes. Ces relations sont de nature semi-structurée : elles associent des éléments faisant référence à des structures de connaissance définies a priori, dans le cas présent les entités qu elles relient, et des éléments donnés uniquement sous la forme d une caractérisation linguistique, en l occurrence leur type. Leur extraction est réalisée en deux temps : des relations candidates sont d'abord extraites sur la base de critères simples mais efficaces pour être ensuite filtrées selon des critères plus avancés. Ce filtrage associe lui-même deux étapes : une première étape utilise des heuristiques pour éliminer rapidement les fausses relations en conservant un bon rappel tandis qu'une seconde étape se fonde sur des modèles statistiques pour raffiner la sélection des relations candidates.Le regroupement de relations a quant à lui un double objectif : d une part, organiser les relations extraites pour en caractériser le type au travers du regroupement des relations sémantiquement équivalentes et d autre part, en offrir une vue synthétique. Il est réalisé dans le cas présent selon une stratégie multiniveau permettant de prendre en compte à la fois un volume important de relations et des critères de regroupement élaborés. Un premier niveau de regroupement, dit de base, réunit des relations proches par leur expression linguistique grâce à une mesure de similarité vectorielle appliquée à une représentation de type sac-de-mots pour former des clusters fortement homogènes. Un second niveau de regroupement est ensuite appliqué pour traiter des phénomènes plus sémantiques tels que la synonymie et la paraphrase et fusionner des clusters de base recouvrant des relations équivalentes sur le plan sémantique. Ce second niveau s'appuie sur la définition de mesures de similarité au niveau des mots, des relations et des clusters de relations en exploitant soit des ressources de type WordNet, soit des thésaurus distributionnels. Enfin, le travail illustre l intérêt de la mise en œuvre d un clustering des relations opéré selon une dimension thématique, en complément de la dimension sémantique des regroupements évoqués précédemment. Ce clustering est réalisé de façon indirecte au travers du regroupement des contextes thématiques textuels des relations. Il offre à la fois un axe supplémentaire de structuration des relations facilitant leur appréhension globale mais également le moyen d invalider certains regroupements sémantiques fondés sur des termes polysémiques utilisés avec des sens différents. La thèse aborde également le problème de l'évaluation de l'extraction d'information non supervisée par l'entremise de mesures internes et externes. Pour les mesures externes, une méthode interactive est proposée pour construire manuellement un large ensemble de clusters de référence. Son application sur un corpus journalistique de grande taille a donné lieu à la construction d'une référence vis-à-vis de laquelle les différentes méthodes de regroupement proposées dans la thèse ont été évaluées.Unsupervised information extraction in open domain gains more and more importance recently by loosening the constraints on the strict definition of the extracted information and allowing to design more open information extraction systems. In this new domain of unsupervised information extraction, this thesis focuses on the tasks of extraction and clustering of relations between entities at a large scale. The objective of relation extraction is to discover unknown relations from texts. A relation prototype is first defined, with which candidates of relation instances are initially extracted with a minimal criterion. To guarantee the validity of the extracted relation instances, a two-step filtering procedures is applied: the first step with filtering heuristics to remove efficiently large amount of false relations and the second step with statistical models to refine the relation candidate selection. The objective of relation clustering is to organize extracted relation instances into clusters so that their relation types can be characterized by the formed clusters and a synthetic view can be offered to end-users. A multi-level clustering procedure is design, which allows to take into account the massive data and diverse linguistic phenomena at the same time. First, the basic clustering groups similar relation instances by their linguistic expressions using only simple similarity measures on a bag-of-word representation for relation instances to form high-homogeneous basic clusters. Second, the semantic clustering aims at grouping basic clusters whose relation instances share the same semantic meaning, dealing with more particularly phenomena such as synonymy or more complex paraphrase. Different similarities measures, either based on resources such as WordNet or distributional thesaurus, at the level of words, relation instances and basic clusters are analyzed. Moreover, a topic-based relation clustering is proposed to consider thematic information in relation clustering so that more precise semantic clusters can be formed. Finally, the thesis also tackles the problem of clustering evaluation in the context of unsupervised information extraction, using both internal and external measures. For the evaluations with external measures, an interactive and efficient way of building reference of relation clusters proposed. The application of this method on a newspaper corpus results in a large reference, based on which different clustering methods are evaluated.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF