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It has been hypothesized that Tree Adjoining Grammar (TAG) is particularly well suited for sentence generation. It is unclear, however, how a sentence generation system based on TAG should choose among the syntactic possibilities made available in the grammar. In this paper we consider the question of what needs to be done to generate with TAGs and explain a generation system that provides the necessary features. This approach is compared with other TAG-based generation systems. Particular attention is given to Mumble-86 which, like our system, makes syntactic choice on sophisticated functional grounds. . | A Functional Approach to Generation with TAG1 Kathleen F. McCoy K. Vijay-Shanker Gijoo Yang Department of Computer and Information Sciences University of Delaware Newark Delaware 19716 USA email mccoy@udel.edu vijay@udel.edu Abstract It has been hypothesized that Tree Adjoining Grammar TAG is particularly well suited for sentence generation. It is unclear however how a sentence generation system based on TAG should choose among the syntactic possibilities made available in the grammar. In this paper we consider the question of what needs to be done to generate with TAGs and explain a generation system that provides the necessary features. This approach is compared with other TAG-based generation systems. Particular attention is given to Mumble-86 which like our system makes syntactic choice on sophisticated functional grounds. 1 Introduction Joshi 1987 described the relevance of Tree Adjoining Grammar TAG Joshi 1985 Schabes Abeille Joshi 1988 to Natural Language Generation. In particular he pointed out how the unique factoring of recursion and dependencies provided by TAG made it particularly appropriate to derive sentence structures from an input provided by a text planning component. Of particular importance is the fact that all syntactic dependencies and function argument structure are localized in TAG trees. Shieber and Schabes 1991 discuss using Synchronous TAG for generation. Synchronous TAG provides a formal foundation to make explicit the relationship between elementary syntactic structures and their corresponding semantic counterparts both expressed as elementary TAG trees. This relationship is made explicit by pairing the elementary trees in the syntactic and logical form languages and associating the corresponding nodes. Shieber and Schabes 1990 describe a generation algorithm which parses an input logical form string recording the adjoining and substitution operations necessary to build the string from its elementary components. The corresponding .
