394 research outputs found
A Graph-Based Approach for the Summarization of Scientific Articles
Automatic text summarization is one of the eminent applications in the field of
Natural Language Processing. Text summarization is the process of generating
a gist from text documents. The task is to produce a summary which contains
important, diverse and coherent information, i.e., a summary should be self-contained.
The approaches for text summarization are conventionally extractive.
The extractive approaches select a subset of sentences from an input document
for a summary. In this thesis, we introduce a novel graph-based extractive summarization
approach.
With the progressive advancement of research in the various fields of science,
the summarization of scientific articles has become an essential requirement for
researchers. This is our prime motivation in selecting scientific articles as our
dataset. This newly formed dataset contains scientific articles from the PLOS
Medicine journal, which is a high impact journal in the field of biomedicine.
The summarization of scientific articles is a single-document summarization task.
It is a complex task due to various reasons, one of it being, the important information
in the scientific article is scattered all over it and another reason being, scientific
articles contain numerous redundant information. In our approach, we deal
with the three important factors of summarization: importance, non-redundancy
and coherence. To deal with these factors, we use graphs as they solve data sparsity
problems and are computationally less complex.
We employ bipartite graphical representation for the summarization task, exclusively.
We represent input documents through a bipartite graph that consists of
sentence nodes and entity nodes. This bipartite graph representation contains entity
transition information which is beneficial for selecting the relevant sentences
for a summary. We use a graph-based ranking algorithm to rank the sentences in
a document. The ranks are considered as relevance scores of the sentences which
are further used in our approach.
Scientific articles contain reasonable amount of redundant information, for example,
Introduction and Methodology sections contain similar information regarding
the motivation and approach. In our approach, we ensure that the summary contains
sentences which are non-redundant.
Though the summary should contain important and non-redundant information of
the input document, its sentences should be connected to one another such that
it becomes coherent, understandable and simple to read. If we do not ensure
that a summary is coherent, its sentences may not be properly connected. This
leads to an obscure summary. Until now, only few summarization approaches
take care of coherence. In our approach, we take care of coherence in two different
ways: by using the graph measure and by using the structural information. We
employ outdegree as the graph measure and coherence patterns for the structural
information, in our approach.
We use integer programming as an optimization technique, to select the best subset
of sentences for a summary. The sentences are selected on the basis of relevance,
diversity and coherence measure. The computation of these measures is
tightly integrated and taken care of simultaneously.
We use human judgements to evaluate coherence of summaries. We compare
ROUGE scores and human judgements of different systems on the PLOS Medicine
dataset. Our approach performs considerably better than other systems on this
dataset. Also, we apply our approach on the standard DUC 2002 dataset to compare
the results with the recent state-of-the-art systems. The results show that our
graph-based approach outperforms other systems on DUC 2002. In conclusion,
our approach is robust, i.e., it works on both scientific and news articles. Our
approach has the further advantage of being semi-supervised
Integrating lexical and prosodic features for automatic paragraph segmentation
Spoken documents, such as podcasts or lectures, are a growing presence in everyday life. Being able to automatically
identify their discourse structure is an important step to understanding what a spoken document is about. Moreover,
finer-grained units, such as paragraphs, are highly desirable for presenting and analyzing spoken content. However, little
work has been done on discourse based speech segmentation below the level of broad topics. In order to examine how
discourse transitions are cued in speech, we investigate automatic paragraph segmentation of TED talks using lexical
and prosodic features. Experiments using Support Vector Machines, AdaBoost, and Neural Networks show that models
using supra-sentential prosodic features and induced cue words perform better than those based on the type of lexical
cohesion measures often used in broad topic segmentation. Moreover, combining a wide range of individually weak
lexical and prosodic predictors improves performance, and modelling contextual information using recurrent neural
networks outperforms other approaches by a large margin. Our best results come from using late fusion methods that
integrate representations generated by separate lexical and prosodic models while allowing interactions between these
features streams rather than treating them as independent information sources. Application to ASR outputs shows that
adding prosodic features, particularly using late fusion, can significantly ameliorate decreases in performance due to
transcription errors.The second author was funded from the EU’s Horizon
2020 Research and Innovation Programme under the GA
H2020-RIA-645012 and the Spanish Ministry of Economy
and Competitivity Juan de la Cierva program. The other
authors were funded by the University of Edinburgh
Automatic Paragraph Segmentation with Lexical and Prosodic Features
Comunicació presentada a la Interspeech 2016, celebrada per la International Speech Communication Association (ISCA) els dies 8 a 12 de septembre de 2016 a San Francisco (EUA).As long-form spoken documents become more ubiquitous in everyday life, so does the need for automatic discourse segmentation in spoken language processing tasks. Although previous work has focused on broad topic segmentation, detection of finer-grained discourse units, such as paragraphs, is highly desirable for presenting and analyzing spoken content. To better understand how different aspects of speech cue these subtle discourse transitions, we investigate automatic paragraph segmentation of TED talks. We build lexical and prosodic paragraph segmenters using Support Vector Machines, AdaBoost, and Long Short Term Memory (LSTM) recurrent neural networks. In general, we find that induced cue words and supra-sentential prosodic features outperform features based on topical coherence, syntactic form and complexity. However, our best performance is achieved by combining a wide range of individually weak lexical and prosodic features, with the sequence modelling LSTM generally outperforming the other classifiers by a large margin. Moreover, we find that models that allow lower level interactions between different feature types produce better results than treating lexical and prosodic contributions as separate, independent information sources.The second author is funded from the EU’s Horizon 2020 Research and Innovation Programme under the GA H2020-RIA-645012 and the Spanish Ministry of Economy and Competitivity Juan de la Cierva program
Semantics-driven Abstractive Document Summarization
The evolution of the Web over the last three decades has led to a deluge of scientific and news articles on the Internet. Harnessing these publications in different fields of study is critical to effective end user information consumption. Similarly, in the domain of healthcare, one of the key challenges with the adoption of Electronic Health Records (EHRs) for clinical practice has been the tremendous amount of clinical notes generated that can be summarized without which clinical decision making and communication will be inefficient and costly. In spite of the rapid advances in information retrieval and deep learning techniques towards abstractive document summarization, the results of these efforts continue to resemble extractive summaries, achieving promising results predominantly on lexical metrics but performing poorly on semantic metrics. Thus, abstractive summarization that is driven by intrinsic and extrinsic semantics of documents is not adequately explored. Resources that can be used for generating semantics-driven abstractive summaries include: • Abstracts of multiple scientific articles published in a given technical field of study to generate an abstractive summary for topically-related abstracts within the field, thus reducing the load of having to read semantically duplicate abstracts on a given topic. • Citation contexts from different authoritative papers citing a reference paper can be used to generate utility-oriented abstractive summary for a scientific article. • Biomedical articles and the named entities characterizing the biomedical articles along with background knowledge bases to generate entity and fact-aware abstractive summaries. • Clinical notes of patients and clinical knowledge bases for abstractive clinical text summarization using knowledge-driven multi-objective optimization. In this dissertation, we develop semantics-driven abstractive models based on intra- document and inter-document semantic analyses along with facts of named entities retrieved from domain-specific knowledge bases to produce summaries. Concretely, we propose a sequence of frameworks leveraging semantics at various granularity (e.g., word, sentence, document, topic, citations, and named entities) levels, by utilizing external resources. The proposed frameworks have been applied to a range of tasks including 1. Abstractive summarization of topic-centric multi-document scientific articles and news articles. 2. Abstractive summarization of scientific articles using crowd-sourced citation contexts. 3. Abstractive summarization of biomedical articles clustered based on entity-relatedness. 4. Abstractive summarization of clinical notes of patients with heart failure and Chest X-Rays recordings. The proposed approaches achieve impressive performance in terms of preserving semantics in abstractive summarization while paraphrasing. For summarization of topic-centric multiple scientific/news articles, we propose a three-stage approach where abstracts of scientific articles or news articles are clustered based on their topical similarity determined from topics generated using Latent Dirichlet Allocation (LDA), followed by extractive phase and abstractive phase. Then, in the next stage, we focus on abstractive summarization of biomedical literature where we leverage named entities in biomedical articles to 1) cluster related articles; and 2) leverage the named entities towards guiding abstractive summarization. Finally, in the last stage, we turn to external resources such as citation contexts pointing to a scientific article to generate a comprehensive and utility-centric abstractive summary of a scientific article, domain-specific knowledge bases to fill gaps in information about entities in a biomedical article to summarize and clinical notes to guide abstractive summarization of clinical text. Thus, the bottom-up progression of exploring semantics towards abstractive summarization in this dissertation starts with (i) Semantic Analysis of Latent Topics; builds on (ii) Internal and External Knowledge-I (gleaned from abstracts and Citation Contexts); and extends it to make it comprehensive using (iii) Internal and External Knowledge-II (Named Entities and Knowledge Bases)
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