76 research outputs found
Representation learning for dialogue systems
Cette thèse présente une série de mesures prises pour étudier l’apprentissage de représentations (par exemple, l’apprentissage profond) afin de mettre en place des systèmes de dialogue et des agents de conversation virtuels. La thèse est divisée en deux parties générales. La première partie de la thèse examine l’apprentissage des représentations pour les modèles de dialogue génératifs. Conditionnés sur une séquence de tours à partir d’un dialogue textuel, ces modèles ont la tâche de générer la prochaine réponse appropriée dans le dialogue. Cette partie de la thèse porte sur les modèles séquence-à -séquence, qui est une classe de réseaux de neurones profonds génératifs. Premièrement, nous proposons un modèle d’encodeur-décodeur récurrent hiérarchique ("Hierarchical Recurrent Encoder-Decoder"), qui est une extension du modèle séquence-à -séquence traditionnel incorporant la structure des tours de dialogue. Deuxièmement, nous proposons un modèle de réseau de neurones récurrents multi-résolution ("Multiresolution Recurrent Neural Network"), qui est un modèle empilé séquence-à -séquence avec une représentation stochastique intermédiaire (une "représentation grossière") capturant le contenu sémantique abstrait communiqué entre les locuteurs. Troisièmement, nous proposons le modèle d’encodeur-décodeur récurrent avec variables latentes ("Latent Variable Recurrent Encoder-Decoder"), qui suivent une distribution normale. Les variables latentes sont destinées à la modélisation de l’ambiguïté et l’incertitude qui apparaissent naturellement dans la communication humaine. Les trois modèles sont évalués et comparés sur deux tâches de génération de réponse de dialogue: une tâche de génération de réponses sur la plateforme Twitter et une tâche de génération de réponses de l’assistance technique ("Ubuntu technical response generation task"). La deuxième partie de la thèse étudie l’apprentissage de représentations pour un système de dialogue utilisant l’apprentissage par renforcement dans un contexte réel. Cette partie porte plus particulièrement sur le système "Milabot" construit par l’Institut québécois d’intelligence artificielle (Mila) pour le concours "Amazon Alexa Prize 2017". Le Milabot est un système capable de bavarder avec des humains sur des sujets populaires à la fois par la parole et par le texte. Le système consiste d’un ensemble de modèles de récupération et de génération en langage naturel, comprenant des modèles basés sur des références, des modèles de sac de mots et des variantes des modèles décrits ci-dessus. Cette partie de la thèse se concentre sur la tâche de sélection de réponse. À partir d’une séquence de tours de dialogues et d’un ensemble des réponses possibles, le système doit sélectionner une réponse appropriée à fournir à l’utilisateur. Une approche d’apprentissage par renforcement basée sur un modèle appelée "Bottleneck Simulator" est proposée pour sélectionner le candidat approprié pour la réponse. Le "Bottleneck Simulator" apprend un modèle approximatif de l’environnement en se basant sur les trajectoires de dialogue observées et le "crowdsourcing", tout en utilisant un état abstrait représentant la sémantique du discours. Le modèle d’environnement est ensuite utilisé pour apprendre une stratégie d’apprentissage du renforcement par le biais de simulations. La stratégie apprise a été évaluée et comparée à des approches concurrentes via des tests A / B avec des utilisateurs réel, où elle démontre d’excellente performance.This thesis presents a series of steps taken towards investigating representation learning (e.g. deep learning) for building dialogue systems and conversational agents. The thesis is split into two general parts. The first part of the thesis investigates representation learning for generative dialogue models. Conditioned on a sequence of turns from a text-based dialogue, these models are tasked with generating the next, appropriate response in the dialogue. This part of the thesis focuses on sequence-to-sequence models, a class of generative deep neural networks. First, we propose the Hierarchical Recurrent Encoder-Decoder model, which is an extension of the vanilla sequence-to sequence model incorporating the turn-taking structure of dialogues. Second, we propose the Multiresolution Recurrent Neural Network model, which is a stacked sequence-to-sequence model with an intermediate, stochastic representation (a "coarse representation") capturing the abstract semantic content communicated between the dialogue speakers. Third, we propose the Latent Variable Recurrent Encoder-Decoder model, which is a variant of the Hierarchical Recurrent Encoder-Decoder model with latent, stochastic normally-distributed variables. The latent, stochastic variables are intended for modelling the ambiguity and uncertainty occurring naturally in human language communication. The three models are evaluated and compared on two dialogue response generation tasks: a Twitter response generation task and the Ubuntu technical response generation task. The second part of the thesis investigates representation learning for a real-world reinforcement learning dialogue system. Specifically, this part focuses on the Milabot system built by the Quebec Artificial Intelligence Institute (Mila) for the Amazon Alexa Prize 2017 competition. Milabot is a system capable of conversing with humans on popular small talk topics through both speech and text. The system consists of an ensemble of natural language retrieval and generation models, including template-based models, bag-of-words models, and variants of the models discussed in the first part of the thesis. This part of the thesis focuses on the response selection task. Given a sequence of turns from a dialogue and a set of candidate responses, the system must select an appropriate response to give the user. A model-based reinforcement learning approach, called the Bottleneck Simulator, is proposed for selecting the appropriate candidate response. The Bottleneck Simulator learns an approximate model of the environment based on observed dialogue trajectories and human crowdsourcing, while utilizing an abstract (bottleneck) state representing high-level discourse semantics. The learned environment model is then employed to learn a reinforcement learning policy through rollout simulations. The learned policy has been evaluated and compared to competing approaches through A/B testing with real-world users, where it was found to yield excellent performance
Two Handy Geometric Prediction Methods of Cancer Growth
In present day societies, cancer is a widely spread disease that affects a large proportion of the human population, many research teams are developing algorithms to help medics to understand this disease. In particular, tumor growth has been studied from different viewpoints and different mathematical models have been proposed. Our aim is to make predictions about shape growth, where shapes are given as domains bounded by a closed curve in R2.
These predictions are based on geometric properties of plane curves and vectors. We propose two methods of prediction and a comparison between them is shared. Both methods can be used to study the evolution in time of any 2D and 3D geometrical forms such as cancer skin and other types of cancer boundary. The first method is based on observations in the normal direction to the plane curve (boundary) at each point (normal method). The second method is based on observations at the growing boundaries in radial directions from the "center" of the shape (radius method). The real data consist of at least two input curves that bind a plane domain
Multiresolution Recurrent Neural Networks: An Application to Dialogue Response Generation
We introduce the multiresolution recurrent neural network, which extends the
sequence-to-sequence framework to model natural language generation as two
parallel discrete stochastic processes: a sequence of high-level coarse tokens,
and a sequence of natural language tokens. There are many ways to estimate or
learn the high-level coarse tokens, but we argue that a simple extraction
procedure is sufficient to capture a wealth of high-level discourse semantics.
Such procedure allows training the multiresolution recurrent neural network by
maximizing the exact joint log-likelihood over both sequences. In contrast to
the standard log- likelihood objective w.r.t. natural language tokens (word
perplexity), optimizing the joint log-likelihood biases the model towards
modeling high-level abstractions. We apply the proposed model to the task of
dialogue response generation in two challenging domains: the Ubuntu technical
support domain, and Twitter conversations. On Ubuntu, the model outperforms
competing approaches by a substantial margin, achieving state-of-the-art
results according to both automatic evaluation metrics and a human evaluation
study. On Twitter, the model appears to generate more relevant and on-topic
responses according to automatic evaluation metrics. Finally, our experiments
demonstrate that the proposed model is more adept at overcoming the sparsity of
natural language and is better able to capture long-term structure.Comment: 21 pages, 2 figures, 10 table
A Hierarchical Latent Variable Encoder-Decoder Model for Generating Dialogues
Sequential data often possesses a hierarchical structure with complex
dependencies between subsequences, such as found between the utterances in a
dialogue. In an effort to model this kind of generative process, we propose a
neural network-based generative architecture, with latent stochastic variables
that span a variable number of time steps. We apply the proposed model to the
task of dialogue response generation and compare it with recent neural network
architectures. We evaluate the model performance through automatic evaluation
metrics and by carrying out a human evaluation. The experiments demonstrate
that our model improves upon recently proposed models and that the latent
variables facilitate the generation of long outputs and maintain the context.Comment: 15 pages, 5 tables, 4 figure
Generating Factoid Questions With Recurrent Neural Networks: The 30M Factoid Question-Answer Corpus
Over the past decade, large-scale supervised learning corpora have enabled
machine learning researchers to make substantial advances. However, to this
date, there are no large-scale question-answer corpora available. In this paper
we present the 30M Factoid Question-Answer Corpus, an enormous question answer
pair corpus produced by applying a novel neural network architecture on the
knowledge base Freebase to transduce facts into natural language questions. The
produced question answer pairs are evaluated both by human evaluators and using
automatic evaluation metrics, including well-established machine translation
and sentence similarity metrics. Across all evaluation criteria the
question-generation model outperforms the competing template-based baseline.
Furthermore, when presented to human evaluators, the generated questions appear
comparable in quality to real human-generated questions.Comment: 13 pages, 1 figure, 7 table
EFFECT OF 12-MONTH RESISTANCE TRAINING ON PHYSICAL FUNCTION IN POSTMENOPAUSAL WOMEN WITH OSTEOPENIA OR OSTEOPOROSIS: A PILOT STUDY
Objective. The present study aimed to evaluate the effects of 12-month resistance training (6 reps x 70% of 1RM + 6 reps x 50% of 1RM) in physical performance in women with postmenopausal osteoporosis or osteopenia. Methods: Ten women with postmenopausal osteopenia/osteoporosis were divided into a exercise group (EX, n = 5) and control group (C, n = 5). The training program included exercises for upper and lower limb muscles with intensities of 50 – 70% of 1RM over a period of 12 months (twice weekly, 50 minutes training session). Physical performance was evaluated before and at the end of the study using the 30-second sit to stand test 30-second arm-curl test. Results: At the end of the study, the results of 10 patients were analyzed. A significant improvement was noted in physical performance for exercise group compared to control group: arm curl test (22.2±0.8 vs. 20.2±0.8, p = .014, r = -0.78) and chair stand test (19.8±0.8 vs. 17.6±1.7, p = .023, r = -0.72). Conclusion: Resistance training program improves physical performance among women with postmenopausal osteopenia/osteoporosis.
REZUMAT. Efectele programului de antrenament cu rezistență pe o perioadă de 12 luni asupra performanțelor fizice la femeile cu osteopenie/osteoporoză postmenopauză: studiu pilot. Obiectiv: Studiul de față a urmărit să evalueze efectele antrenamentului de rezistență de 12 luni (6 repetări x 70% din 1RM + 6 repetări x 50% din 1RM) asupra performanțelor fizice la femeile cu osteoporoză sau osteopenie postmenopauză. Material și metode: Zece femei cu osteopenie / osteoporoză postmenopauză au fost împărțite într-o grupă experimentală (EX, n = 5) și grupă de control (C, n = 5). Programul de antrenament a inclus exerciții pentru mușchii membrelor superioare și inferioare, cu intensități de 50 - 70% din 1RM pe o perioadă de 12 luni (de două ori pe săptămână, 50 minute sesiunea de antrenament). Performanța fizică a fost evaluată înainte și la sfârșitul studiului, folosind testul de flexie a antebrațului pe brat în 30 de secunde cu o ganteră de 2 kg în mână (arm curl test) și testul de ridicare din așezat în stând în 30 de secunde (chair stand test). Rezultate: La sfârșitul studiului, au fost analizate rezultatele a 10 subiecți. S-a observat o îmbunătățire semnificativă a performanței fizice în cadrul grupei experimentale, în comparație cu grupa de control: testul de flexie a antebrațului pe braț (22.2 ± 0.8 vs. 20.2 ± 0.8, p = 0.014, r = -0.78) și testul de ridicare din așezat în stând (19.8 ± 0.8 vs. 17.6 ± 1.7, p = 0.023, r = -0.72). Concluzie: Programul de exerciții cu rezistență îmbunătățește performanța fizică în rândul femeilor cu osteopenie / osteoporoză postmenopauză.
Cuvinte cheie: osteoporoză, osteopenie, antrenament de forță, postmenopauză, performanță fizică
A Survey of Available Corpora For Building Data-Driven Dialogue Systems: The Journal Version
During the past decade, several areas of speech and language understanding have witnessed substantial breakthroughs from the use of data-driven models. In the area of dialogue systems, the trend is less obvious, and most practical systems are still built through significant engineering and expert knowledge. Nevertheless, several recent results suggest that data-driven approaches are feasible and quite promising. To facilitate research in this area, we have carried out a wide survey of publicly available datasets suitable for data-driven learning of dialogue systems. We discuss important characteristics of these datasets, how they can be used to learn diverse dialogue strategies, and their other potential uses. We also examine methods for transfer learning between datasets and the use of external knowledge. Finally, we discuss appropriate choice of evaluation metrics for the learning objective
Training End-to-End Dialogue Systems with the Ubuntu Dialogue Corpus
In this paper, we construct and train end-to-end neural network-based dialogue systems usingan updated version of the recent Ubuntu Dialogue Corpus, a dataset containing almost 1 million multi-turn dialogues, with a total of over 7 million utterances and 100 million words. This dataset is interesting because of its size, long context lengths, and technical nature; thus, it can be used to train large models directly from data with minimal feature engineering, which can be both time consuming and expensive. We provide baselines in two different environments: one where models are trained to maximize the log-likelihood of a generated utterance conditioned on the context of the conversation, and one where models are trained to select the correct next response from a list of candidate responses. These are both evaluated on a recall task that we call Next Utterance Classification (NUC), as well as other generation-specific metrics. Finally, we provide a qualitative error analysis to help determine the most promising directions for future research on the Ubuntu Dialogue Corpus, and for end-to-end dialogue systems in general
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