tailieunhanh - Báo cáo khoa học: "Constraint Based Integration of Deep and Shallow Parsing Techniques"

To investigate the contributions of taggers or chunkers to the performance of a deep syntactic parser, Weighted Constraint Dependency Grammars have been extended to also take into consideration information from external sources. Using a weak information fusion scheme based on constraint optimization techniques, a parsing accuracy has been achieved which is comparable to other (stochastic) parsers. | Constraint Based Integration of Deep and Shallow Parsing Techniques Michael Daum and Kilian A. Foth and Wolfgang Menzel Natural Language Systems Department of Computer Science University of Hamburg micha foth wolfgang @nats . informatik . uni-hamburg. de Abstract To investigate the contributions of taggers or chunkers to the performance of a deep syntactic parser Weighted Constraint Dependency Grammars have been extended to also take into consideration information from external sources. Using a weak information fusion scheme based on constraint optimization techniques a parsing accuracy has been achieved which is comparable to other stochastic parsers. 1 Introduction To investigate the contributions of different shallow processing components like taggers or chunkers to the performance of a deep syntactic parser Weighted Constraint Dependency Grammars WCDG have been extended to also take into consideration information from external sources. Constraints in the WCDG framework are partially defeasible conditions on admissible structural configurations in a dependency tree for a given natural language utterance. By defining conditions 1 on word forms and their positional relationships 2 on links between word forms and 3 on the labels attached to these links they license certain dependency relations or combinations thereof and assign a score to them. These scores give an estimate of the appropriateness of a particular partial structure. Constraint optimization techniques are used to obtain the structure with the best overall score which is chosen as the optimal representation of the utterance. Due to the use of weighted constraints throughout the grammar WCDG comes with a number of advantages A WCDG grammar is able to accomodate conflicting requirements as they can often be found in natural language . in case of ordering preferences. WCDG shares this property with Optimality Theory Prince and Smolensky forthc . Since constraints can be violated the grammar also .