Type-Driven Semantic Interpretation of f-Structures

[ Type-Driven Semantic Interpretation of f-Structures ] ¿.~,w),(njO) Jiirgen Wedekind Institute for Natural Language Processing University of Stuttgart Azenbergstr. 12 D-7000 Stuttgart 1, FRG juergen@ims.uni-stuttgart.de Ronald M. Kaplan Xerox Palo Alto Research Center 3333 Coyote Hill Road Palo Alto, California 94304 USA Kaplan.Parc@Xerox.Com Abstract The formal architecture of Lexical Func- tional Grammar offers a particular formal device, the structural correspondence, for modularizing the mapping between the sur- face forms of a language and representa- tions of their underlying meanings. This approach works well when the structural discrepancies between form and meaning representations are finitely bounded, but there are some phenomena in natural lan- guage, e.g. adverbs in English, where this restriction does not hold. In this paper, we describe rule-based type-driven interpreta- tion algorithms which cover cases of such a structural misalignment by exploiting a new descriptive device, the "restriction op- erator". The algorithms are set up in such a way that recursive rules can be derived for the interpretation of adjunct sets within a codescripiion approach (see [Kaplan and Wedekind, 1993] for details). 1 Introduction In [Kaplan and Bresnan, 1982] Lexical Functional Grammar (LFG) was introduced as a grammatical formalism that assigns to a sentence entities of two different levels of representation: a c-structure rep- resenting information on the structure of the phrases of a sentence and an f-structure which represents its underlying predicate-argument structure. The struc- tures are set in correspondence by a function from the c-structure nodes (constituents) into the sub- structures of the f-structure. The f-structure is iden- tified with the smallest structure that satisfies the f-description, a description of the f-structure which is built up by instantiation of the annotations of the context-free rules and projected off the c-structure by the correspondence mapping. This architecture was then extended by Kaplan [1987] and Halvorsen [1987] to structures represent- ing information on other levels of linguistic repre- sentation. These structures (called projections) are codescribed by the annotations of the context-free grammar and set in correspondence by additional projectors. Furthermore, Kaplan et ai. [1989] applied the general correspondence architecture to the prob- lem of translation by projecting from the f-structure of a sentence of a given source language an addi- tional f-structure of its translation into some target language. Within the domain of semantic interpretation, which is the topic here, the semantic structures are the range of the a-projector which maps substruc- tures of the f-structure into corresponding substruc- tures of the semantic structure. In figure 1, the S ........ rPaED 'arrive(SUB J)' 1 P VP ":/ su~Ja, [PRED Jonn J N , --': t..- , ]J/ i-.. i /.j k N " .... Z:~ "/'~ PP~L~. arrive] I "-. .J*'" / ~ . . / John ""arrived L.~,.G1 3ohn J Figure 1 Structural correspondences between c-, f- and a-structure. semantic structure ((r-structure) and the structural correspondence between f- and a-structure for the sentence John arrived are codescribed by additional 404 annotations of the lexical entry for arrived in (1). (1) arrived: V, (T PrtED)= "arrive(SUDJ)' (a T …

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