A Context-free Approximation of Head-driven Phrase Structure Grammar
Bernd Kiefer, Hans‐Ulrich Krieger · International Workshop/Conference on Parsing Technologies · 2000
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.