CLI Speaker Series

• [Mon Oct 22 2007 4:00-5:30] (ICC450)

  Speaker: Janet Hitzeman (MITRE)
  Topic: "SpatialML: A Proposed Standard for GeoSpatial Annotation"

• [Fri Nov 2 2007 3:30-5:00]

  Speaker: John Hale (Michigan State University)
  
  Topic: "QUANTIFYING AMBIGUITY RESOLUTION WITH INFORMATION THEORY"
  
  Abstract: Ambiguities about grammatical category and syntactic structure permeate natural language. Explaining human comprehenders' performance in the face of such confusion has been called the central problem in sentence processing (Tabor & Tanenhaus, 2001). How is it that human sentence understanders are able to recognize combinatory relationships, from an infinite range of possibilities, to arrive at a meaningful interpretation of a sentence?
  
  This talk argues that an answer lies in formalizing the idea that comprehenders search the space of grammatical analyses in a way constrained by the words they hear. Comprehenders are constantly engaged in ambiguity resolution, and the more ambiguity is resolved, the longer they take.
  
  To make this intuition fully explicit, ambiguity resolution will be given a precise interpretation in terms of information theory.
  
  The general theory is tested using explicit grammar fragments that are probabilistic versions of Generalized Phrase Structure Grammars (Gazdar, Klein & Sag 1985) and Minimalist Grammars (Stabler 1997). The theory will be shown to derive a range of well-documented processing phenomena including garden-path sentences, center-embedding, and the Accessibility (or Obliqueness) Hierarchy of relativized grammatical functions.
  
  Gerald Gazdar, Ewan Klein, Geoffrey Pullum and Ivan Sag. 1985. Generalized Phrase Structure Grammar. Harvard University Press. Whitney Tabor and Michael K. Tanenhaus. 2001. ``Dynamical Systems for Sentence Processing'' in Connectionist Psycholinguistics, edited by Morten H. Christiansen and Nick Chater. Ablex. Edward P. Stabler, Jr. 1997. ``Derivational Minimalism'' in Logical Aspects of Computational Linguistics, edited by Christian Retore. Springer-Verlag.

• [Mon Nov 12 2007 3:30-5:00]

  Speaker: Jerry Hobbs (ISI/USC)
  
  Topic: An Ontology of Time
  
  I will first describe the OWL-Time ontology that was developed in conjunction with the DARPA Agent Markup Language (DAML) program. It covers the topological properties of time, including Allen's interval relations, measures of duration, and the clock and calendar, all axiomatized in first-order predicate calculus. I will then describe our effort to axiomatize temporal aggregates, such as "every third Monday of every other month". In developing all of this, we have attempted to cover a wide range of natural language constructions as well as subsume the coverage of existing calendar systems. Finally, I will describe our work on annotating events in newspaper articles with the range in which their duration is likely to fall. Here we have developed annotation guidelines to disambiguate the most common uncertain cases, we have developed an approach to measuring inter-annotator agreement, and we have performed some modestly successful machine learning experiments on this data. All of this represents joint work with Feng Pan and Rutu Mehta.