randy%iaisun%sbsvax.uucp(3)Germany.CSnet Following on research that resulted in the translation methodology known as the <C,A>,T framework, the present paper reports on the further development and implementation now referred to as CAT2. The basic philosophy is the creation of separate grammars, in homogeneous notation, for multiple levels of linguistic representation, and a means of describing relations between the levels. Each level is represented as a derivation tree generated by a context-free grammar augmented by feature lists. The translation relations are recursive tree-to-tree mappings. The basic operation is unification, making CAT2 similar to unificationbased formalisms. As a development tool, it shares many characteristics of PATR-II. The descriptive nature of the framework motivates the use of Prolog as the implementation language. The report describes the CAT2 formalism and its implementation. Some comparisons are made between CAT2 and similar frameworks. An example is presented showing the basic strategy in analysis,

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.