The UniTN Discourse Parser in CoNLL 2015 Shared Task: Token-level Sequence Labeling with Argument-specific Models

Penn Discourse Treebank style discourse parsing is a composite task of identifying discourse relations (explicit or nonexplicit), their connective and argument spans, and assigning a sense to these relations from the hierarchy of senses. In this paper we describe University of Trento parser submitted to CoNLL 2015 Shared Task on Shallow Discourse Parsing. The span detection tasks for explicit relations are cast as token-level sequence labeling. The argument span decisions are conditioned on relations’ being intraor intersentential. Non-explicit relation detection and sense assignment tasks are cast as classification. In the end-to-end closedtrack evaluation, the parser ranked second with a global F-measure of 0.2184