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"Topic": models, code, and papers

Low-Resource Adaptation of Neural NLP Models

Nov 09, 2020
Farhad Nooralahzadeh

Real-world applications of natural language processing (NLP) are challenging. NLP models rely heavily on supervised machine learning and require large amounts of annotated data. These resources are often based on language data available in large quantities, such as English newswire. However, in real-world applications of NLP, the textual resources vary across several dimensions, such as language, dialect, topic, and genre. It is challenging to find annotated data of sufficient amount and quality. The objective of this thesis is to investigate methods for dealing with such low-resource scenarios in information extraction and natural language understanding. To this end, we study distant supervision and sequential transfer learning in various low-resource settings. We develop and adapt neural NLP models to explore a number of research questions concerning NLP tasks with minimal or no training data.

* Thesis submitted for the degree of Philosophiae Doctor. Department of Informatics, University of Oslo. https://www.mn.uio.no/ifi/forskning/aktuelt/arrangementer/disputaser/2020/nooralahzadeh.html 

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Multiple Texts as a Limiting Factor in Online Learning: Quantifying (Dis-)similarities of Knowledge Networks across Languages

Aug 05, 2020
Alexander Mehler, Wahed Hemati, Pascal Welke, Maxim Konca, Tolga Uslu

We test the hypothesis that the extent to which one obtains information on a given topic through Wikipedia depends on the language in which it is consulted. Controlling the size factor, we investigate this hypothesis for a number of 25 subject areas. Since Wikipedia is a central part of the web-based information landscape, this indicates a language-related, linguistic bias. The article therefore deals with the question of whether Wikipedia exhibits this kind of linguistic relativity or not. From the perspective of educational science, the article develops a computational model of the information landscape from which multiple texts are drawn as typical input of web-based reading. For this purpose, it develops a hybrid model of intra- and intertextual similarity of different parts of the information landscape and tests this model on the example of 35 languages and corresponding Wikipedias. In this way the article builds a bridge between reading research, educational science, Wikipedia research and computational linguistics.

* 40 pages, 13 figures, 5 tables 

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Machine learning on Big Data from Twitter to understand public reactions to COVID-19

May 18, 2020
Jia Xue, Junxiang Chen, Chen Chen, ChengDa Zheng, Tingshao Zhu

The study aims to understand Twitter users' discussions and reactions about the COVID-19. We use machine learning techniques to analyze about 1.8 million Tweets messages related to coronavirus collected from January 20th to March 7th, 2020. A total of "cases outside China (worldwide)," "COVID-19 outbreak in South Korea," "early signs of the outbreak in New York," "Diamond Princess cruise," "economic impact," "Preventive/Protective measures," "authorities," and "supply chain". Results do not reveal treatment and/or symptoms related messages as a prevalent topic on Twitter. We also run sentiment analysis and the results show that trust for the authorities remained a prevalent emotion, but mixed feelings of trust for authorities, fear for the outbreak, and anticipation for the potential preventive measures will be taken are identified. Implications and limitations of the study are also discussed.


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Generating Persona-Consistent Dialogue Responses Using Deep Reinforcement Learning

Apr 30, 2020
Mohsen Mesgar, Edwin Simpson, Yue Wang, Iryna Gurevych

Recent transformer-based open-domain dialogue agents are trained by reference responses in a fully supervised scenario. Such agents often display inconsistent personalities as training data potentially contain contradictory responses to identical input utterances and no persona-relevant criteria are used in their training losses. We propose a novel approach to train transformer-based dialogue agents using actor-critic reinforcement learning. We define a new reward function to assess generated responses in terms of persona consistency, topic consistency, and fluency. Our reference-agnostic reward relies only on a dialogue history and a persona defined by a list of facts. Automatic and human evaluations on the PERSONACHAT dataset show that our proposed approach increases the rate of persona-consistent responses compared with its peers that are trained in a fully supervised scenario using reference responses.


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Towards Prediction Explainability through Sparse Communication

Apr 28, 2020
Marcos V. Treviso, André F. T. Martins

Explainability is a topic of growing importance in NLP. In this work, we provide a unified perspective of explainability as a communication problem between an explainer and a layperson about a classifier's decision. We use this framework to compare several prior approaches for extracting explanations, including gradient methods, representation erasure, and attention mechanisms, in terms of their communication success. In addition, we reinterpret these methods at the light of classical feature selection, and we use this as inspiration to propose new embedded methods for explainability, through the use of selective, sparse attention. Experiments in text classification, natural language entailment, and machine translation, using different configurations of explainers and laypeople (including both machines and humans), reveal an advantage of attention-based explainers over gradient and erasure methods. Furthermore, human evaluation experiments show promising results with post-hoc explainers trained to optimize communication success and faithfulness.


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Do sequence-to-sequence VAEs learn global features of sentences?

Apr 16, 2020
Tom Bosc, Pascal Vincent

A longstanding goal in NLP is to compute global sentence representations. Such representations would be useful for sample-efficient semi-supervised learning and controllable text generation. To learn to represent global and local information separately, Bowman & al. (2016) proposed to train a sequence-to-sequence model with the variational auto-encoder (VAE) objective. What precisely is encoded in these latent variables expected to capture global features? We measure which words benefit most from the latent information by decomposing the reconstruction loss per position in the sentence. Using this method, we see that VAEs are prone to memorizing the first words and the sentence length, drastically limiting their usefulness. To alleviate this, we propose variants based on bag-of-words assumptions and language model pretraining. These variants learn latents that are more global: they are more predictive of topic or sentiment labels, and their reconstructions are more faithful to the labels of the original documents.


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The Enron Corpus: Where the Email Bodies are Buried?

Jan 24, 2020
David Noever

To probe the largest public-domain email database for indicators of fraud, we apply machine learning and accomplish four investigative tasks. First, we identify persons of interest (POI), using financial records and email, and report a peak accuracy of 95.7%. Secondly, we find any publicly exposed personally identifiable information (PII) and discover 50,000 previously unreported instances. Thirdly, we automatically flag legally responsive emails as scored by human experts in the California electricity blackout lawsuit, and find a peak 99% accuracy. Finally, we track three years of primary topics and sentiment across over 10,000 unique people before, during and after the onset of the corporate crisis. Where possible, we compare accuracy against execution times for 51 algorithms and report human-interpretable business rules that can scale to vast datasets.


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Towards Generating Explanations for ASP-Based Link Analysis using Declarative Program Transformations

Sep 08, 2019
Martin Atzmueller, Cicek Güven, Dietmar Seipel

The explication and the generation of explanations are prominent topics in artificial intelligence and data science, in order to make methods and systems more transparent and understandable for humans. This paper investigates the problem of link analysis, specifically link prediction and anomalous link discovery in social networks using the declarative method of Answer set programming (ASP). Applying ASP for link prediction provides a powerful declarative approach, e.g., for incorporating domain knowledge for explicative prediction. In this context, we propose a novel method for generating explanations - as offline justifications - using declarative program transformations. The method itself is purely based on syntactic transformations of declarative programs, e.g., in an ASP formalism, using rule instrumentation. We demonstrate the efficacy of the proposed approach, exemplifying it in an application on link analysis in social networks, also including domain knowledge.

* Part of DECLARE 19 proceedings 

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Unsupervised Segmentation of Hyperspectral Images Using 3D Convolutional Autoencoders

Jul 20, 2019
Jakub Nalepa, Michal Myller, Yasuteru Imai, Ken-ichi Honda, Tomomi Takeda, Marek Antoniak

Hyperspectral image analysis has become an important topic widely researched by the remote sensing community. Classification and segmentation of such imagery help understand the underlying materials within a scanned scene, since hyperspectral images convey a detailed information captured in a number of spectral bands. Although deep learning has established the state of the art in the field, it still remains challenging to train well-generalizing models due to the lack of ground-truth data. In this letter, we tackle this problem and propose an end-to-end approach to segment hyperspectral images in a fully unsupervised way. We introduce a new deep architecture which couples 3D convolutional autoencoders with clustering. Our multi-faceted experimental study---performed over benchmark and real-life data---revealed that our approach delivers high-quality segmentation without any prior class labels.

* Submitted to IEEE Geoscience and Remote Sensing Letters 

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A Spatial-temporal 3D Human Pose Reconstruction Framework

Jan 10, 2019
X. T. Nguyen, T. D. Ngo, T. H. Le

3D human pose reconstruction from single-view camera is a difficult and challenging topic. Many approaches have been proposed, but almost focusing on frame-by-frame independently while inter-frames are highly correlated in a pose sequence. In contrast, we introduce a novel spatial-temporal 3D reconstruction framework that leverages both intra and inter frame relationships in consecutive 2D pose sequences. Orthogonal Matching Pursuit (OMP) algorithm, pre-trained Pose-angle Limits and Temporal Models have been implemented. We quantitatively compare our framework versus recent works on CMU motion capture dataset and Vietnamese traditional dance sequences. Our method outperforms others with 10 percent lower of Euclidean reconstruction error and robustness against Gaussian noise. Additionally, it is also important to mention that our reconstructed 3D pose sequences are smoother and more natural than others.

* 10 pages. JIPS Journal 2018 

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