@inproceedings{kiefer-krieger-2000-context,
    title = "A Context-free Approximation of {H}ead-driven {P}hrase {S}tructure {G}rammar",
    author = "Kiefer, Bernd  and
      Krieger, Hans-Ulrich",
    editor = "Lavelli, Alberto  and
      Carroll, John  and
      Berwick, Robert C.  and
      Bunt, Harry C.  and
      Carpenter, Bob  and
      Carroll, John  and
      Church, Ken  and
      Johnson, Mark  and
      Joshi, Aravind  and
      Kaplan, Ronald  and
      Kay, Martin  and
      Lang, Bernard  and
      Lavie, Alon  and
      Nijholt, Anton  and
      Samuelsson, Christer  and
      Steedman, Mark  and
      Stock, Oliviero  and
      Tanaka, Hozumi  and
      Tomita, Masaru  and
      Uszkoreit, Hans  and
      Vijay-Shanker, K.  and
      Weir, David  and
      Wiren, Mats",
    booktitle = "Proceedings of the Sixth International Workshop on Parsing Technologies",
    month = feb # " 23-25",
    year = "2000",
    address = "Trento, Italy",
    publisher = "Association for Computational Linguistics",
    url = "https://preview.aclanthology.org/ingest-emnlp/2000.iwpt-1.15/",
    pages = "135--146",
    abstract = "We present a context-free approximation of unification-based grammars, such as HPSG or PATR-II. The theoretical underpinning is established through a least fixpoint construction over a certain monotonic function. In order to reach a finite fixpoint, the concrete implementation can be parameterized in several ways , either by specifying a finite iteration depth, by using different restrictors, or by making the symbols of the CFG more complex adding annotations a la GPSG. We also present several methods that speed up the approximation process and help to limit the size of the resulting CF grammar."
}