Extraction de patrons sémantiques appliquée à la classification d'Entités Nommées

International audienceLa variabilité des corpus constitue un problème majeur pour les systèmes de reconnaissance d'entités nommées. L'une des pistes possibles pour y remédier est l'utilisation d'approches linguistiques pour les adapter à de nouveaux contextes : la construction de patrons sémantiques peut permettre de désambiguïser les entités nommées en structurant leur environnement syntaxico-sémantique. Cet article présente une première réalisation sur un corpus de presse d'un système de correction. Après une étape de segmentation sur des critères discursifs de surface, le système extrait et pondère les patrons liés à une classe d'entité nommée fournie par un analyseur. Malgré des modèles encore relativement élémentaires, les résultats obtenus sont encourageants et montrent la nécessité d'un traitement plus approfondi de la classe Organisation. Abstract Corpus variation is a major problem for named entity recognition systems. One possible direction to tackle this problem involves using linguistic approaches to adapt them to unseen contexts : building semantic patterns may help for their disambiguation by structuring their syntactic and semantic environment. This article presents a preliminary implementation on a press corpus of a correction system. After a segmentation step based on surface discourse clues, the system extracts and weights the patterns linked to a named entity class provided by an analyzer. Despite relatively elementary models, the results obtained are promising and point on the necessary treatment of the Organisation class. Mots-clés : entités nommées, patrons sémantiques, segmentation discursive de surface Keywords: named entities, semantic patterns, surface discourse segmentation ISMAÏL EL MAAROUF, JEANNE VILLANEAU, SOPHIE ROSSE

Towards an automatic speech recognition system for use by deaf students in lectures

According to the Royal National Institute for Deaf people there are nearly 7.5 million hearing-impaired people in Great Britain. Human-operated machine transcription systems, such as Palantype, achieve low word error rates in real-time. The disadvantage is that they are very expensive to use because of the difficulty in training operators, making them impractical for everyday use in higher education. Existing automatic speech recognition systems also achieve low word error rates, the disadvantages being that they work for read speech in a restricted domain. Moving a system to a new domain requires a large amount of relevant data, for training acoustic and language models. The adopted solution makes use of an existing continuous speech phoneme recognition system as a front-end to a word recognition sub-system. The subsystem generates a lattice of word hypotheses using dynamic programming with robust parameter estimation obtained using evolutionary programming. Sentence hypotheses are obtained by parsing the word lattice using a beam search and contributing knowledge consisting of anti-grammar rules, that check the syntactic incorrectness’ of word sequences, and word frequency information. On an unseen spontaneous lecture taken from the Lund Corpus and using a dictionary containing "2637 words, the system achieved 815% words correct with 15% simulated phoneme error, and 73.1% words correct with 25% simulated phoneme error. The system was also evaluated on 113 Wall Street Journal sentences. The achievements of the work are a domain independent method, using the anti- grammar, to reduce the word lattice search space whilst allowing normal spontaneous English to be spoken; a system designed to allow integration with new sources of knowledge, such as semantics or prosody, providing a test-bench for determining the impact of different knowledge upon word lattice parsing without the need for the underlying speech recognition hardware; the robustness of the word lattice generation using parameters that withstand changes in vocabulary and domain

Desenvolvimento de um sistema de diálogo para interação com robôs

Mestrado em Engenharia de Computadores e TelemáticaService robots operate in the same environment as humans and perform actions that a human usually performs. These robots must be able to operate autonomously in unknown and dynamic environments, as well as to maneuver with several people and know how to deal with them. By complying with these requirements, they are able to successfully address humans and fulfill their requests whenever they need assistance in a certain task. Natural language communication, including speech that is the most natural way of communication between humans, becomes relevant in the field of Human-Robot Interaction (HRI). By endowing service robots with intuitive spoken interfaces, the specification of the human required tasks is facilitated. However, this is a complicated task to achieve due to the resources involved in creating a sufficiently intuitive spoken interface and because of the difficulty of deploying it in different robots. The main objective of this thesis is the definition, implementation and evaluation of a dialogue system that can be easily integrated into any robotic platform and that functions as a flexible base for the creation of any conversational scenario in the Portuguese language. The system must meet the basic requirements for intuitive and natural communications, namely the characteristics of human-human conversations. A system was developed that functions as a base to give continuity to future work on Spoken Dialog Systems. The system incorporates the client-server architecture, where the client runs on the robot and captures what the user says. The client takes advantage on external dialogue management services. They are executed by the server, which processes the audio obtained, returning an appropriate response given the context of the dialogue. The development was based on a critical analysis of the state of the art in order for the system to be as faithful as possible to what is already done. Through the evaluation phase of the system, it was managed to obtain by few volunteers the conclusion that the main objective was accomplished: a base system was created that is flexible enough to explore different contexts of conversation, such as interacting with children or providing information on a university environment.Os robôs de serviço operam no mesmo ambiente dos humanos e executam ações que um humano normalmente executaria. Estes robôs devem ser capazes de operar de forma autónoma em ambientes desconhecidos e dinâmicos, assim como de manobrar em ambientes com várias pessoas e de saberem lidar com elas. Ao respeitarem estes requisitos, conseguirão abordar com sucesso os humanos e cumprir as suas solicitações sempre que estes precisem de assistência em alguma tarefa. A comunicação por linguagem natural, nomeadamente a fala que é a forma mais abrangente de comunicação entre humanos, torna-se relevante na área da Interação humano-robô (IHR). Ao dotar os robôs de serviço com sistemas de voz intuitivos facilita-se a especificação das tarefas a realizar. No entanto, é uma tarefa complicada de se realizar devido aos recursos envolvidos na criação de uma interação suficientemente intuitiva e devido à dificuldade de funcionar em diversos robôs. O objetivo principal deste trabalho é a definição, implementação e avaliação de um sistema de diálogo que seja de fácil integração em qualquer sistema robótico e que funcione como uma base flexível para qualquer cenário de conversação na língua Portuguesa. Deve obedecer a requisitos base de comunicação intuitiva e natural, nomeadamente a características de conversas entre humanos. Foi desenvolvido um sistema que funciona como uma base para dar continuidade a trabalho futuro em sistemas de diálogo. O sistema incorpora a arquitetura cliente-servidor onde o cliente é executado no robô e capta o que o utilizador diz. O cliente tira partido de serviços de gestão de diálogo externos ao robô, executados pelo servidor, que processa o áudio obtido, devolvendo uma resposta ao cliente adequada ao contexto do diálogo. O desenvolvimento foi baseado numa análise crítica do estado da arte para se tentar manter fiel ao que já foi feito e de forma a se tomarem as principais decisões durante a implementação. Mediante a fase de avaliação do sistema, tanto a nível do ponto de vista da interação como do programador, conseguiu-se obter por parte de alguns voluntários que o objetivo principal foi cumprido: foi criada uma base suficientemente flexível para explorar diferentes contextos de conversação, nomeadamente interagir com crianças ou fornecimento de informações em ambiente universitário

Speech understanding in open tasks

The Air Traffic Information Service task is currently used by DARPA as a common evaluation task for Spoken Language Systems. This task is an example of open type tasks. Subjects are given a task and allowed to interact spontaneously with the system by voice. There is no fixed lexicon or grammar, and subjects are likely to exceed those used by any given system. In order to evaluate system performance on such tasks, a common corpus of training data has been gathered and annotated. An independent test corpus was also created in a similar fashion. This paper explains the techniques used in our system and the performance results on the standard set of tests used to evaluate systems