PhD defence by Dongsheng Wang

Portræt af Dongsheng Wang

Title  

Semantic Representation and Inference for NLP

Abstract

Semantic representation and inference is essential for Natural Language Processing (NLP). The state of the art for semantic representation and inference is deep learning, and particularly Recurrent Neural Networks (RNNs), Convolutional Neural Networks (CNNs), and Self-Attention models. This thesis investigates the use of deep learning for novel semantic representation and inference, and makes contributions in the following three areas: creating training data, improving semantic representations and extending inference learning.

In terms of creating training data, we contribute the largest publicly available dataset of real-life factual claims for the purpose of automatic claim verification (MultiFC), and we present a novel inference model composed of multi-scale CNNs with different kernel sizes that learn from external sources to infer fact checking labels. In terms of improving semantic representations, we contribute a novel model that captures non-compositional semantic indicators. By definition, the meaning of a non-compositional phrase cannot be inferred from the individual meanings of its composing words (e.g., hot dog). Motivated by this, we operationalize the compositionality of a phrase contextually by enriching the phrase representation with external word embeddings and knowledge graphs. Finally, in terms of inference learning, we propose a series of novel deep learning architectures that improve inference by using syntactic dependencies, by ensembling role guided attention heads, incorporating gating layers, and concatenating multiple heads in novel and effective ways. This thesis consists of seven publications (five published and two under review).

Assessment Committee

Chairperson: Associate professor, Erik B. Dam, Department of Computer Science, UCPH
Associate professor, Haiming Liu, Bedfordshire University
Associate professor, Toine Bogers, Aalborg University

Academic supervisors

Professor Christina Lioma and Professor Jakob Grue Simonsen, both from the Department of Computer Science, University of Copenhagen

Moderator

Maria Maistro, tenure track assistant professor, Department of Computer Science,
University of Copenhagen


For an electronic copy of the thesis, please contact phdadmin@di.ku.dk