24 research outputs found
Hypothesis Only Baselines in Natural Language Inference
We propose a hypothesis only baseline for diagnosing Natural Language
Inference (NLI). Especially when an NLI dataset assumes inference is occurring
based purely on the relationship between a context and a hypothesis, it follows
that assessing entailment relations while ignoring the provided context is a
degenerate solution. Yet, through experiments on ten distinct NLI datasets, we
find that this approach, which we refer to as a hypothesis-only model, is able
to significantly outperform a majority class baseline across a number of NLI
datasets. Our analysis suggests that statistical irregularities may allow a
model to perform NLI in some datasets beyond what should be achievable without
access to the context.Comment: Accepted at *SEM 2018 as long paper. 12 page
From Paraphrase Database to Compositional Paraphrase Model and Back
The Paraphrase Database (PPDB; Ganitkevitch et al., 2013) is an extensive
semantic resource, consisting of a list of phrase pairs with (heuristic)
confidence estimates. However, it is still unclear how it can best be used, due
to the heuristic nature of the confidences and its necessarily incomplete
coverage. We propose models to leverage the phrase pairs from the PPDB to build
parametric paraphrase models that score paraphrase pairs more accurately than
the PPDB's internal scores while simultaneously improving its coverage. They
allow for learning phrase embeddings as well as improved word embeddings.
Moreover, we introduce two new, manually annotated datasets to evaluate
short-phrase paraphrasing models. Using our paraphrase model trained using
PPDB, we achieve state-of-the-art results on standard word and bigram
similarity tasks and beat strong baselines on our new short phrase paraphrase
tasks.Comment: 2015 TACL paper updated with an appendix describing new 300
dimensional embeddings. Submitted 1/2015. Accepted 2/2015. Published 6/201
The Semantic Typology of Visually Grounded Paraphrases
Visually grounded paraphrases (VGPs) are different phrasal expressions describing the same visual concept in an image. Previous studies treat VGP identification as a binary classification task, which ignores various phenomena behind VGPs (i.e., different linguistic interpretation of the same visual concept) such as linguistic paraphrases and VGPs from different aspects. In this paper, we propose semantic typology for VGPs, aiming to elucidate the VGP phenomena and deepen the understanding about how human beings interpret vision with language. We construct a large VGP dataset that annotates the class to which each VGP pair belongs according to our typology. In addition, we present a classification model that fuses language and visual features for VGP classification on our dataset. Experiments indicate that joint language and vision representation learning is important for VGP classification. We further demonstrate that our VGP typology can boost the performance of visually grounded textual entailment
Representation Learning for Words and Entities
This thesis presents new methods for unsupervised learning of distributed
representations of words and entities from text and knowledge bases. The first
algorithm presented in the thesis is a multi-view algorithm for learning
representations of words called Multiview Latent Semantic Analysis (MVLSA). By
incorporating up to 46 different types of co-occurrence statistics for the same
vocabulary of english words, I show that MVLSA outperforms other
state-of-the-art word embedding models. Next, I focus on learning entity
representations for search and recommendation and present the second method of
this thesis, Neural Variational Set Expansion (NVSE). NVSE is also an
unsupervised learning method, but it is based on the Variational Autoencoder
framework. Evaluations with human annotators show that NVSE can facilitate
better search and recommendation of information gathered from noisy, automatic
annotation of unstructured natural language corpora. Finally, I move from
unstructured data and focus on structured knowledge graphs. I present novel
approaches for learning embeddings of vertices and edges in a knowledge graph
that obey logical constraints.Comment: phd thesis, Machine Learning, Natural Language Processing,
Representation Learning, Knowledge Graphs, Entities, Word Embeddings, Entity
Embedding
From Word to Sense Embeddings: A Survey on Vector Representations of Meaning
Over the past years, distributed semantic representations have proved to be
effective and flexible keepers of prior knowledge to be integrated into
downstream applications. This survey focuses on the representation of meaning.
We start from the theoretical background behind word vector space models and
highlight one of their major limitations: the meaning conflation deficiency,
which arises from representing a word with all its possible meanings as a
single vector. Then, we explain how this deficiency can be addressed through a
transition from the word level to the more fine-grained level of word senses
(in its broader acceptation) as a method for modelling unambiguous lexical
meaning. We present a comprehensive overview of the wide range of techniques in
the two main branches of sense representation, i.e., unsupervised and
knowledge-based. Finally, this survey covers the main evaluation procedures and
applications for this type of representation, and provides an analysis of four
of its important aspects: interpretability, sense granularity, adaptability to
different domains and compositionality.Comment: 46 pages, 8 figures. Published in Journal of Artificial Intelligence
Researc
Automatic Image Captioning with Style
This thesis connects two core topics in machine learning, vision
and language. The problem of choice is image caption generation:
automatically constructing natural language descriptions of image
content. Previous research into image caption generation has
focused on generating purely descriptive captions; I focus on
generating visually relevant captions with a distinct linguistic
style. Captions with style have the potential to ease
communication and add a new layer of personalisation.
First, I consider naming variations in image captions, and
propose a method for predicting context-dependent names that
takes into account visual and linguistic information. This method
makes use of a large-scale image caption dataset, which I also
use to explore naming conventions and report naming conventions
for hundreds of animal classes. Next I propose the SentiCap
model, which relies on recent advances in artificial neural
networks to generate visually relevant image captions with
positive or negative sentiment. To balance descriptiveness and
sentiment, the SentiCap model dynamically switches between two
recurrent neural networks, one tuned for descriptive words and
one for sentiment words. As the first published model for
generating captions with sentiment, SentiCap has influenced a
number of subsequent works. I then investigate the sub-task of
modelling styled sentences without images. The specific task
chosen is sentence simplification: rewriting news article
sentences to make them easier to understand.
For this task I design a neural sequence-to-sequence model that
can work with
limited training data, using novel adaptations for word copying
and sharing
word embeddings. Finally, I present SemStyle, a system for
generating visually
relevant image captions in the style of an arbitrary text corpus.
A shared term
space allows a neural network for vision and content planning to
communicate
with a network for styled language generation. SemStyle achieves
competitive
results in human and automatic evaluations of descriptiveness and
style.
As a whole, this thesis presents two complete systems for styled
caption generation that are first of their kind and demonstrate,
for the first time, that automatic style transfer for image
captions is achievable. Contributions also include novel ideas
for object naming and sentence simplification. This thesis opens
up inquiries into highly personalised image captions; large scale
visually grounded concept naming; and more generally, styled text
generation with content control
Representation Learning for Words and Entities
This thesis presents new methods for unsupervised learning of distributed representations of words and entities from text and knowledge bases. The first algorithm presented in the thesis is a multi-view algorithm for learning representations of words called Multiview LSA (MVLSA). Through experiments on close to 50 different views, I show that MVLSA outperforms other state-of-the-art word embedding models. After that, I focus on learning entity representations for search and recommendation and present the second algorithm of this thesis called Neural Variational Set Expansion (NVSE). NVSE is also an unsupervised learning method, but it is based on the Variational Autoencoder framework. Evaluations with human annotators show that NVSE can facilitate better search and recommendation of information gathered from noisy, automatic annotation of unstructured natural language corpora. Finally, I move from unstructured data and focus on structured knowledge graphs. Moreover, I present novel approaches for learning embeddings of vertices and edges in a knowledge graph that obey logical constraints