Cg3

Tools for the Constraint Grammar formalism

Constraint Grammar CG parsers are at the core of most of VISL’s live applications. The Constraint Grammar concept was launched by Fred Karlsson in the early 90’ies Karlsson et.al.1995, and CG parsers have since been written for a large variety of languages, routinely achieving F-scores for PoS word class of over 99. A number of syntactic CG systems have reported F-scores of around 95. VISL’s own Constraint Grammar systems are inspired by Eckhard Bick’s PALAVRAS parser for Portuguese Bick 2000, and use, as a novelty, subclause function, generalized dependency markers and semantic prototype tags. For most languages, a lexicon based morphological analyzer provides input to the first CG level, while the output of the last CG-level can be converted into syntactic tree structures by specially designed Phrase Structure Grammars PSG’s, using syntactic functions, not words, as terminals. Other, hybrid combinations are, however, feasible. Thus, the French system uses PoS information from a probabilistic tagger.