Parsing by Successive Approximation

It is proposed to parse feature structure-based grammars in several steps. Each step is aimed to eliminate as many invalid analyses as possible as e ciently as possible. To this end the set of feature constraints is divided into three subsets, a set of context-free constraints, a set of ltering constraints and a set of structure-building constraints, which are solved in that order. The best processing strategy di ers: Context-free constraints are solved e ciently with one of the well-known algorithms for context-free parsing. Filtering constraints can be solved using uni cation algorithms for non-disjunctive feature structures whereas structure-building constraints require special techniques to represent feature structures with embedded disjunctions e ciently. A compilation method and an e cient processing strategy for ltering constraints are presented.