Generation in Machine Translation from Deep Syntactic Trees
What it is about
The authors generate English from Praguian tectogrammatical trees, which keep content words, functors and grammatemes and drop the function words. Generation has two statistical parts. First, classifiers predict the auxiliary words that the tree lacks (articles, prepositions and subordinating conjunctions, and modal verbs by a fixed map), each from the node's lemma, tag and functor and its governor's. When a classifier is unsure (probability below 0.5), a few fixed rules apply, such as to before infinitives and of before actors. Second, a bottom-up procedure orders each head's children, scoring pairs by tag and functor, and places the governor. On PCEDT 1.0 the article accuracy was about 89–90% on manual trees and the preposition and conjunction accuracy about 89–92%; reordering was scored by whether all children of a node come out in order. The BLEU of the full system was about 0.46 on manual trees.
Ideas
- I1. Insertion from frame roles. For each meta token, predict the function word (article, preposition) from its concept, tag and frame role (
prag), with governor features, through a backoff chain of count tables in BTreeMap form. Measure the accuracy per class on dev, as the paper reports it. - I2. Fallbacks from counts. Where the top count probability is below 0.5, let the encoder fall back to the most frequent insertion for the same role, instead of a hand list. Compare both at the same threshold.
- I3. A strict reorder metric. Score the linearizer (
en/src/lin.rs) with the paper's rule that a node counts as right only when all its children are in order, a harder measure than pairwise order. - I4. Article definiteness from the text. The paper inserts the when the noun appeared in the previous four sentences. A verse window of the same kind, with the source text's earlier mentions, is a feature for the encoder's article class.
For Mova
The paper is a generator from a deep tree with few words, which is close to the meta-world read from frames. Its strict reorder metric and its classifier-accuracy tables are measures Mova can copy, and the fallback to counts matches Mova's rule of learning from data rather than from hand lists.
Cite
@inproceedings{hall2007generation,
title = {{Generation in Machine Translation from Deep Syntactic Trees}},
author = {Hall, Keith and Němec, Petr},
booktitle = {Proceedings of SSST, NAACL-HLT 2007 / AMTA Workshop on Syntax and Structure in Statistical Translation},
year = {2007},
doi = {10.3115/1626281.1626289},
url = {https://doi.org/10.3115/1626281.1626289}
}References
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