SMT Errors Requiring Grammatical Knowledge for Prevention
Summary
The paper presents a qualitative analysis of errors in English-to-Japanese statistical machine translation (SMT). The author manually tested the online system Google Language Tools on individual sentences. She identified three classes of errors that, in her view, cannot be avoided without grammatical knowledge. The first class concerns words that have a negative meaning but no negative form (few, little, seldom, hardly, etc.). In Japanese, such sentences require explicit negation in the predicate. The system, however, often translates these words as "a few" or "almost", which reverses the meaning. The second class arises from inserted adverbials that break up fixed constructions, so the system no longer recognizes them. The third class is related to ellipsis. Constituents omitted in the English sentence must be restored when Japanese omission rules or a different Head-Complement order require it. The paper contains no quantitative evaluation. The author concludes that such cases require syntactic analysis and grammatical rules, and that statistics alone are not enough. The paper shows the weak points of SMT for language pairs with very different grammars.
Key points
- The object of study is English-Japanese translation in the Google Language Tools service. The method is manual analysis of examples, without a corpus or metrics.
- Words with implicit negation: the determiners few and little, and the adverbs little, seldom, rarely, scarcely, hardly and barely. The part of speech must be determined, since few can be a determiner, a pronoun or an adjective. The system translated sentences with little attention and was hardly surprising with the opposite meaning. By contrast, it translated could/can hardly constructions almost correctly.
- Adverbials such as so far or long inside template phrases like "unable to …" or "have been geared" spoil the translation. When the insertion is removed, the result becomes correct. The author mentions the controlled skip parser (Yamada, 1996), but cautions that negative adverbs must not be skipped.
- Ellipsis: the omitted "those who" must be restored in the Japanese translation. The elliptical comparisons as much and half as long also proved problematic.
- Conclusion: adding new templates for each case is impractical. Syntactic parsing and rules for recognition and generation are needed.
Cite
@inproceedings{alam2015smt,
title = {{SMT Errors Requiring Grammatical Knowledge for Prevention}},
author = {Alam, Yukiko Sasaki},
booktitle = {Proceedings of the 12th International Conference on Natural Language Processing},
year = {2015},
url = {https://aclanthology.org/W15-5923/}
}References
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