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Currently several grammatical formalisms converge towards being declarative and towards utilizing context-free phrase-structure grammar as a backbone, e.g. L F G and PATR-II. Typically the processing of these formalisms is organized within a chart-parsing framework. The declarative character of the formalisms makes it important to decide upon an overall optimal control strategy on the part of the processor. In particular, this brings the ruleinvocation strategy into criticalfocus: to gain maximal processing efficiency, one has to determine the best way of putting the rules to use. The aim of this paper is to provide a survey and a practical comparison. | A Comparison of Rule-Invocation Strategies in Context-Free Chart Parsing Mats Wiren Department of Computer and Information Science Linkõping University S-58183 Linkõping Sweden Abstract Currently several grammatical formalisms converge towards being declarative and towards utilizing context-free phrase-structure grammar as a backbone e.g. LFG and PATR-II. Typically the processing of these formalisms is organized within a chart-parsing framework. The declarative character of the formalisms makes it important to decide upon an overall optimal control strategy on the part of the processor. In particular this brings the ruleinvocation strategy into critical focus to gain maximal processing efficiency one has to determine the best way of putting the rules to use. The aim of this paper is to provide a survey and a practical comparison of fundamental rule-invocation strategies within context-free chart parsing. 1 Background and Introduction An apparent tendency in computational linguistics during the last few years has been towards declarative grammar formalisms. This tendency has manifested itself with respect to linguistic tools perhaps seen most clearly in the evolution from ATNs with their strongly procedural grammars to PATR-II in its various incarnations Shieber et al. 1983 Kart-tunen 1986 and to logic-based formalisms such as DCG Pereira and Warren 1980 . It has also manifested itself in linguistic theories where there has been a development from systems employing sequential derivations in the analysis of sentence structures to systems like LFG and GPSG which establish relations among the elements of a sentence in an order-independent and also direction-independent way. For example phenomena such as rule ordering simply do not arise in these theories. This research has been supported by the National Swedish Board for Technical Development. In addition declarative formalisms are in principle processor-independent. Procedural formalisms although possibly highly .
