Computational Linguistics & Phonetics Computational Linguistics & Phonetics Fachrichtung 4.7 Universität des Saarlandes

Computational Linguistics Colloquium

Thursday, 13 January 2011, 16:15
Conference Room, Building C7 4

A TAG formalism for Parsing and Translation

Xavier Carreras
Universitat Politecnica de Catalunya (UPC)

Syntactic parsing is the fundamental problem of determining the structure of natural language sentences. It is a challenging task, because syntactic structures of natural languages are recursive, and there is a significant degree of ambiguity in determining how different parts of a sentence combine together syntactically. In any computational model for parsing, the choice of grammar formalism is critical to both the representational power of the model and its computational efficiency. In this talk I will describe a variant of a Tree Adjoining Grammar (TAG) that can use a wide varitey of rich features and, at the same time, has efficient algorithms. I will present two applications of our TAG. The first is a discriminative parser, a generalization of Conditional Random Fields for structured prediction that extends the framework to syntactic parsing. The second application is machine translation, where we frame the problem as a parsing task. The TAG-based translation system makes direct use of syntactic structures in modeling differences in word order between different languages, and in modeling the grammaticality of translation output. In both applications we show improvements over state-of-the-art systems. This is joint work with Michael Collins and Terry Koo.

If you would like to meet with the speaker, please contact Ivan Titov.