From Treebank Parses to Episodic Logic and Commonsense Inference

We have developed an approach to broad-coverage semantic parsing that starts with Treebank parses and yields scoped, deindexed formulas in Episodic Logic (EL) that are directly usable for knowledgebased inference. Distinctive properties of our approach are • the use of a tree transduction language, TTT, to partially disambiguate, refine (and sometimes repair) raw Treebank parses, and also to perform many deindexing and logical canonicalization tasks; • the use of EL, a Montague-inspired logical framework for semantic representation and knowledge representation; • allowance for nonclassical restricted quantifiers, several forms of modification and reification, quasi-quotes and syntactic closures; • an event semantics that directly represents events with complex characterizations; • a scoping algorithm that heuristically scopes quantifiers, logical connectives, and tense; • a compositional approach to tense deindexing making use of tense trees; and • the use of an inference engine, EPILOG, that supports input-driven and goal-driven inference in EL, in a style similar to (but more general than) Natural Logic.