Wide-coverage semantic analysis with Boxer
Johan Bos · 2008
Boxer is an open-domain software component for semantic analysis of text, based on Combinatory Categorial Grammar (CCG) and Discourse Representation Theory (DRT).Used together with the C&C tools, Boxer reaches more than 95% coverage on newswire texts.The semantic representations produced by Boxer, known as Discourse Representation Structures (DRSs), incorporate a neo-Davidsonian representations for events, using the VerbNet inventory of thematic roles.The resulting DRSs can be translated to ordinary first-order logic formulas and be processing by standard theorem provers for first-order logic.Boxer's performance on the shared task for comparing semantic represtations was promising.It was able to produce complete DRSs for all seven texts.Manually inspecting the output revealed that: (a) the computed predicate argument structure was generally of high quality, in particular dealing with hard constructions involving control or coordination; (b) discourse structure triggered by conditionals, negation or discourse adverbs was overall correctly computed; (c) some measure and time expressions are correctly analysed, others aren't; (d) several shallow analyses are given for lexical phrases that require deep analysis; (e) bridging references and pronouns are not resolved in most cases.Boxer is distributed with the C&C tools and freely available for research purposes.