12,788 research outputs found
Unsupervised Alignment-based Iterative Evidence Retrieval for Multi-hop Question Answering
Evidence retrieval is a critical stage of question answering (QA), necessary
not only to improve performance, but also to explain the decisions of the
corresponding QA method. We introduce a simple, fast, and unsupervised
iterative evidence retrieval method, which relies on three ideas: (a) an
unsupervised alignment approach to soft-align questions and answers with
justification sentences using only GloVe embeddings, (b) an iterative process
that reformulates queries focusing on terms that are not covered by existing
justifications, which (c) a stopping criterion that terminates retrieval when
the terms in the given question and candidate answers are covered by the
retrieved justifications. Despite its simplicity, our approach outperforms all
the previous methods (including supervised methods) on the evidence selection
task on two datasets: MultiRC and QASC. When these evidence sentences are fed
into a RoBERTa answer classification component, we achieve state-of-the-art QA
performance on these two datasets.Comment: Accepted at ACL 2020 as a long conference pape
Quick and (not so) Dirty: Unsupervised Selection of Justification Sentences for Multi-hop Question Answering
We propose an unsupervised strategy for the selection of justification
sentences for multi-hop question answering (QA) that (a) maximizes the
relevance of the selected sentences, (b) minimizes the overlap between the
selected facts, and (c) maximizes the coverage of both question and answer.
This unsupervised sentence selection method can be coupled with any supervised
QA approach. We show that the sentences selected by our method improve the
performance of a state-of-the-art supervised QA model on two multi-hop QA
datasets: AI2's Reasoning Challenge (ARC) and Multi-Sentence Reading
Comprehension (MultiRC). We obtain new state-of-the-art performance on both
datasets among approaches that do not use external resources for training the
QA system: 56.82% F1 on ARC (41.24% on Challenge and 64.49% on Easy) and 26.1%
EM0 on MultiRC. Our justification sentences have higher quality than the
justifications selected by a strong information retrieval baseline, e.g., by
5.4% F1 in MultiRC. We also show that our unsupervised selection of
justification sentences is more stable across domains than a state-of-the-art
supervised sentence selection method.Comment: Published at EMNLP-IJCNLP 2019 as long conference paper. Corrected
the name reference for Speer et.al, 201
Constructing Datasets for Multi-hop Reading Comprehension Across Documents
Most Reading Comprehension methods limit themselves to queries which can be
answered using a single sentence, paragraph, or document. Enabling models to
combine disjoint pieces of textual evidence would extend the scope of machine
comprehension methods, but currently there exist no resources to train and test
this capability. We propose a novel task to encourage the development of models
for text understanding across multiple documents and to investigate the limits
of existing methods. In our task, a model learns to seek and combine evidence -
effectively performing multi-hop (alias multi-step) inference. We devise a
methodology to produce datasets for this task, given a collection of
query-answer pairs and thematically linked documents. Two datasets from
different domains are induced, and we identify potential pitfalls and devise
circumvention strategies. We evaluate two previously proposed competitive
models and find that one can integrate information across documents. However,
both models struggle to select relevant information, as providing documents
guaranteed to be relevant greatly improves their performance. While the models
outperform several strong baselines, their best accuracy reaches 42.9% compared
to human performance at 74.0% - leaving ample room for improvement.Comment: This paper directly corresponds to the TACL version
(https://transacl.org/ojs/index.php/tacl/article/view/1325) apart from minor
changes in wording, additional footnotes, and appendice
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