Development of a Bengali parser by cross-lingual transfer from Hindi

Ayan Das, Agnivo Saha, Sudeshna Sarkar


Abstract
In recent years there has been a lot of interest in cross-lingual parsing for developing treebanks for languages with small or no annotated treebanks. In this paper, we explore the development of a cross-lingual transfer parser from Hindi to Bengali using a Hindi parser and a Hindi-Bengali parallel corpus. A parser is trained and applied to the Hindi sentences of the parallel corpus and the parse trees are projected to construct probable parse trees of the corresponding Bengali sentences. Only about 14% of these trees are complete (transferred trees contain all the target sentence words) and they are used to construct a Bengali parser. We relax the criteria of completeness to consider well-formed trees (43% of the trees) leading to an improvement. We note that the words often do not have a one-to-one mapping in the two languages but considering sentences at the chunk-level results in better correspondence between the two languages. Based on this we present a method to use chunking as a preprocessing step and do the transfer on the chunk trees. We find that about 72% of the projected parse trees of Bengali are now well-formed. The resultant parser achieves significant improvement in both Unlabeled Attachment Score (UAS) as well as Labeled Attachment Score (LAS) over the baseline word-level transferred parser.
Anthology ID:
W16-3704
Volume:
Proceedings of the 6th Workshop on South and Southeast Asian Natural Language Processing (WSSANLP2016)
Month:
December
Year:
2016
Address:
Osaka, Japan
Venues:
WS | WSSANLP
SIG:
Publisher:
The COLING 2016 Organizing Committee
Note:
Pages:
33–43
Language:
URL:
https://aclanthology.org/W16-3704
DOI:
Bibkey:
Cite (ACL):
Ayan Das, Agnivo Saha, and Sudeshna Sarkar. 2016. Development of a Bengali parser by cross-lingual transfer from Hindi. In Proceedings of the 6th Workshop on South and Southeast Asian Natural Language Processing (WSSANLP2016), pages 33–43, Osaka, Japan. The COLING 2016 Organizing Committee.
Cite (Informal):
Development of a Bengali parser by cross-lingual transfer from Hindi (Das et al., 2016)
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PDF:
https://aclanthology.org/W16-3704.pdf