Technical Reports (CIS)

Document Type

Technical Report

Date of this Version

January 2007

Comments

University of Pennsylvania Department of Computer and Information Science Technical Report No. MS-CIS-07-18.

Abstract

Most models used in natural language processing must be trained on large corpora of labeled text. This tutorial explores a "primarily unsupervised" approach (based on graphical models) that augments a corpus of unlabeled text with some form of prior domain knowledge, but does not require any fully labeled examples. We survey probabilistic graphical models for (supervised) classification and sequence labeling and then present the prototype-driven approach of Haghighi and Klein (2006) to sequence labeling in detail, including a discussion of the theory and implementation of both conditional random fields and prototype learning. We show experimental results for English part of speech tagging.

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Date Posted: 04 October 2007