2 research outputs found
Tensors and tensor decompositions for combining external information with knowledge graph embeddings
The task of knowledge graph (KG) completion, where one is given an incomplete KG
as a list of facts, and is asked to give high scores to correct but unseen triples, has
been a well-studied problem in the NLP community. A simple but surprisingly robust
approach for solving this task emerged as learning low dimensional embeddings for
entities and relations by approximating the underlying KG directly through a scoring
function.
Knowledge graphs have a natural representation as a binary three way array, also
known as a 3rd order tensor, and certain classes of scoring functions can be characterized as finding a low-rank decomposition of this tensor. This dissertation extends this
characterization, and investigates the suitability of tensors for modelling both knowledge graphs and related data, for learning low-rank representations of entities and relations that incorporate information from heterogeneous sources, and for reasoning with
paths and rules using the learned representations.
Specifically, we present two joint tensor decomposition models for integrating external
information in the process of learning KG embeddings. Our first model is a joint
tensor-tensor decomposition model that learns representations based on both KG facts
and type information on entities and relations. Our second model is a joint tensor-matrix decomposition for integrating cooccurrence information between entities and
words from an entity linked corpus into knowledge graph embeddings, in order to
learn better representations for the entities that are rarely seen in the knowledge graph.
We also investigate tensors as tools for enabling multi-step reasoning using learned
embedding representations. To this end, we extend theoretical results for semiring
weighted logic programs to tensors of semirings. Our results are broadly applicable
to any area that uses dynamic programming algorithms for calculating tensor values.
Such applications include incorporating embeddings of paths and rules for knowledge
graph completion, and syntactic parsing with latent variable grammar
Sentence entailment in compositional distributional semantics
Distributional semantic models provide vector representations for words by
gathering co-occurrence frequencies from corpora of text. Compositional
distributional models extend these from words to phrases and sentences. In
categorical compositional distributional semantics, phrase and sentence
representations are functions of their grammatical structure and
representations of the words therein. In this setting, grammatical structures
are formalised by morphisms of a compact closed category and meanings of words
are formalised by objects of the same category. These can be instantiated in
the form of vectors or density matrices. This paper concerns the applications
of this model to phrase and sentence level entailment. We argue that
entropy-based distances of vectors and density matrices provide a good
candidate to measure word-level entailment, show the advantage of density
matrices over vectors for word level entailments, and prove that these
distances extend compositionally from words to phrases and sentences. We
exemplify our theoretical constructions on real data and a toy entailment
dataset and provide preliminary experimental evidence.Comment: 8 pages, 1 figure, 2 tables, short version presented in the
International Symposium on Artificial Intelligence and Mathematics (ISAIM),
201