Discourse Relation Embeddings: Representing the Relations between Discourse Segments in Social Media

Discourse relations are typically modeled as a discrete class that characterizes the relation between segments of text (e.g. causal explanations, expansions). However, such predefined discrete classes limit the universe of potential relations and their nuanced differences. Adding higher-level semantic structure to modern contextual word embeddings, we propose representing discourse relations as points in high dimensional continuous space. However, unlike words, discourse relations often have no surface form (relations are inbetween two segments, often with no explicit word or phrase marker), presenting a challenge for existing embedding techniques. We present a novel method for automatically creating discourse relation embeddings (DiscRE), addressing the embedding challenge through a weakly supervised, multitask approach. Results show DiscRE representations obtain the best performance on Twitter discourse relation classification (macro F1 = 0.76) and social media causality prediction (from F1 = .79 to .81), performing beyond modern sentence and word transformers, and capturing novel nuanced relations (e.g. relations at the intersection of causal explanations and counterfactuals).