Accurate unlexicalized parsing for modern hebrew

Reut Tsarfaty, Khalil Sima'An

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


Many state-of-the-art statistical parsers for English can be viewed as Probabilistic Context-Free Grammars (PCFGs) acquired from treebanks consisting of phrase-structure trees enriched with a variety of contextual, derivational (e.g., markovization) and lexical information. In this paper we empirically investigate the applicability and adequacy of the unlexicalized variety of such parsing models to Modem Hebrew, a Semitic language that differs in structure and characteristics from English. We show that contrary to experience with parsing the WSJ, the markovized, head-driven unlexicalized variety does not necessarily outperform plain PCFGs for Semitic languages. We demonstrate that enriching unlexicalized PCFGs with morphologically marked agreement features percolated up the parse tree (e.g., definiteness) outperforms plain PCFGs as well as a simple head-driven variation on the MH treebank. We further show that an (unlexicalized) head-driven variety enriched with the same features achieves even better performance. We conclude that morphologically rich languages introduce an additional dimension of parametrization that is orthogonal to the horizontal/vertical dimensions proposed before [1] and its contribution is essential and complementary.

Original languageEnglish
Title of host publicationText, Speech and Dialogue - 10th International Conference, TSD 2007, Proceedings
PublisherSpringer Verlag
Number of pages9
ISBN (Print)9783540746270
StatePublished - 2007
Externally publishedYes
Event10th International Conference on Text, Speech and Dialogue, TSD 2007 - Pilsen, Czech Republic
Duration: 3 Sep 20077 Sep 2007

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume4629 LNAI
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference10th International Conference on Text, Speech and Dialogue, TSD 2007
Country/TerritoryCzech Republic


Dive into the research topics of 'Accurate unlexicalized parsing for modern hebrew'. Together they form a unique fingerprint.

Cite this