@inproceedings{vilar-etal-2008-analysing,
    title = "Analysing soft syntax features and heuristics for hierarchical phrase based machine translation.",
    author = "Vilar, David  and
      Stein, Daniel  and
      Ney, Hermann",
    booktitle = "Proceedings of the 5th International Workshop on Spoken Language Translation: Papers",
    month = oct # " 20-21",
    year = "2008",
    address = "Waikiki, Hawaii",
    url = "https://preview.aclanthology.org/jlcl-multiple-ingestion/2008.iwslt-papers.7/",
    pages = "190--197",
    abstract = "Similar to phrase-based machine translation, hierarchical systems produce a large proportion of phrases, most of which are supposedly junk and useless for the actual translation. For the hierarchical case, however, the amount of extracted rules is an order of magnitude bigger. In this paper, we investigate several soft constraints in the extraction of hierarchical phrases and whether these help as additional scores in the decoding to prune unneeded phrases. We show the methods that help best."
}