10 research outputs found
Morphological Priors for Probabilistic Neural Word Embeddings
Word embeddings allow natural language processing systems to share
statistical information across related words. These embeddings are typically
based on distributional statistics, making it difficult for them to generalize
to rare or unseen words. We propose to improve word embeddings by incorporating
morphological information, capturing shared sub-word features. Unlike previous
work that constructs word embeddings directly from morphemes, we combine
morphological and distributional information in a unified probabilistic
framework, in which the word embedding is a latent variable. The morphological
information provides a prior distribution on the latent word embeddings, which
in turn condition a likelihood function over an observed corpus. This approach
yields improvements on intrinsic word similarity evaluations, and also in the
downstream task of part-of-speech tagging.Comment: Appeared at the Conference on Empirical Methods in Natural Language
Processing (EMNLP 2016, Austin
Lifted rule injection for relation embeddings
Methods based on representation learning currently hold the state-of-the-art in many natural language processing and knowledge base inference tasks. Yet, a major challenge is how to efficiently incorporate commonsense knowledge into such models. A recent approach regularizes relation and entity representations by propositionalization of first-order logic rules. However, propositionalization does not scale beyond domains with only few entities and rules. In this paper we present a highly efficient method for incorporating implication rules into distributed representations for automated knowledge base construction. We map entity-tuple embeddings into an approximately Boolean space and encourage a partial ordering over relation embeddings based on implication rules mined from WordNet. Surprisingly, we find that the strong restriction of the entity-tuple embedding space does not hurt the expressiveness of the model and even acts as a regularizer that improves generalization. By incorporating few commonsense rules, we achieve an increase of 2 percentage points mean average precision over a matrix factorization baseline, while observing a negligible increase in runtime
Distributional Inclusion Vector Embedding for Unsupervised Hypernymy Detection
Modeling hypernymy, such as poodle is-a dog, is an important generalization
aid to many NLP tasks, such as entailment, coreference, relation extraction,
and question answering. Supervised learning from labeled hypernym sources, such
as WordNet, limits the coverage of these models, which can be addressed by
learning hypernyms from unlabeled text. Existing unsupervised methods either do
not scale to large vocabularies or yield unacceptably poor accuracy. This paper
introduces distributional inclusion vector embedding (DIVE), a
simple-to-implement unsupervised method of hypernym discovery via per-word
non-negative vector embeddings which preserve the inclusion property of word
contexts in a low-dimensional and interpretable space. In experimental
evaluations more comprehensive than any previous literature of which we are
aware-evaluating on 11 datasets using multiple existing as well as newly
proposed scoring functions-we find that our method provides up to double the
precision of previous unsupervised embeddings, and the highest average
performance, using a much more compact word representation, and yielding many
new state-of-the-art results.Comment: NAACL 201
Hypernym Detection Using Strict Partial Order Networks
This paper introduces Strict Partial Order Networks (SPON), a novel neural
network architecture designed to enforce asymmetry and transitive properties as
soft constraints. We apply it to induce hypernymy relations by training with
is-a pairs. We also present an augmented variant of SPON that can generalize
type information learned for in-vocabulary terms to previously unseen ones. An
extensive evaluation over eleven benchmarks across different tasks shows that
SPON consistently either outperforms or attains the state of the art on all but
one of these benchmarks.Comment: 8 page
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Ideal Words: A Vector-Based Formalisation of Semantic Competence
Funder: UniversitĂ degli Studi di TrentoAbstractIn this theoretical paper, we consider the notion of semantic competence and its relation to general language understandingâone of the most sough-after goals of Artificial Intelligence. We come back to three main accounts of competence involving (a) lexical knowledge; (b) truth-theoretic reference; and (c) causal chains in language use. We argue that all three are needed to reach a notion of meaning in artificial agents and suggest that they can be combined in a single formalisation, where competence develops from exposure to observable performance data. We introduce a theoretical framework which translates set theory into vector-space semantics by applying distributional techniques to a corpus of utterances associated with truth values. The resulting meaning space naturally satisfies the requirements of a causal theory of competence, but it can also be regarded as some âidealâ model of the world, allowing for extensions and standard lexical relations to be retrieved.</jats:p
Combining Representation Learning with Logic for Language Processing
The current state-of-the-art in many natural language processing and
automated knowledge base completion tasks is held by representation learning
methods which learn distributed vector representations of symbols via
gradient-based optimization. They require little or no hand-crafted features,
thus avoiding the need for most preprocessing steps and task-specific
assumptions. However, in many cases representation learning requires a large
amount of annotated training data to generalize well to unseen data. Such
labeled training data is provided by human annotators who often use formal
logic as the language for specifying annotations. This thesis investigates
different combinations of representation learning methods with logic for
reducing the need for annotated training data, and for improving
generalization.Comment: PhD Thesis, University College London, Submitted and accepted in 201