Robust Shallow Semantic Parsing of Text

Date

January 26, 2012

Speaker

Dipanjan Das

Affiliation

Carnegie Mellon University

Overview

In this talk, I will focus on data-driven models for semantic structure prediction following frame semantics (Fillmore, 1982), a linguistic theory that describes predicate-argument relationships and emphasizes the abstraction of predicate meaning into semantic frames. Our method exploits rich information provided by linguists in the form of a lexicon (Fillmore and Baker, 2010), as well as a small amount of annotated data, to automatically find disambiguated semantic frames of lexical predicates present in a sentence. A frame represents semantic knowledge and requires semantic roles that are fulfilled by arguments, in the form of words and phrases within the sentence. After disambiguating each predicate to the frame it evokes, our method finds the frame’s arguments collectively via joint inference, making use of dual decomposition. Large amounts of annotated data for this task are unavailable; to this end, we model latent structure and apply semi-supervised learning, resulting in more robust models with broader coverage. Frame semantics is richer than the representation used in popular semantic role labeling systems (Kingsbury and Palmer, 2002) but less domain-specific than semantic parsers based on logical form (Ge and Mooney, 2005; Zettlemoyer and Collins, 2005); it represents a viable “middle ground” for data-driven semantic analysis of text. Compared to previous work, our method makes fewer independence assumptions and significantly outperforms past state of the art.

Speakers

Dipanjan Das

Dipanjan Das is a Ph.D. student at the Language Technologies Institute, School of Computer Science at Carnegie Mellon University. He works on statistical natural language processing under the mentorship of Noah Smith. He finished his M.S. at the same institute in 2008, conducting research on language generation with Alexander Rudnicky. Das completed his undergraduate degree in 2005 from the Indian Institute of Technology, Kharagpur, where he received the best undergraduate thesis award in Computer Science and Engineering and the Dr. B.C. Roy Memorial Gold Medal for best all-round performance in academics and co-curricular activities. He worked at Google Research, New York as an intern in 2010 and received the best paper award at the ACL 2011 conference.