Incremental Parser Generation for Tree Adjoining Grammars

This paper describes the incremental generation of parse tables for the LRtype parsing of Tree Adjoining Languages (TALs). The algorithm presented handles modi cations to the input grammar by updating the parser generated so far. In this paper, a lazy generation of LR-type parsers for TALs is de ned in which parse tables are created by need while parsing. We then describe an incremental parser generator for TALs which responds to modi cation of the input grammar by updating parse tables built so far. 1 LR Parser Generation Tree Adjoining Grammars (TAGs) are tree rewriting systems which combine trees with the single operation of adjoining. (Schabes and Vijay-Shanker, 1990) describes the construction of an LR parsing algorithm for TAGs. Parser generation here is taken to be the construction of LR(0) tables (i.e., without any lookahead) for a particular TAG. The moves This work is partially supported by NSF grant NSFSTC SBR 8920230 ARPA grant N00014-94 and ARO grant DAAH04-94-G0426. Thanks to Breck Baldwin, Dania Egedi, Jason Eisner, B. Srinivas and the three anonymous reviewers for their valuable comments. Familiarity with TAGs and their parsing techniques is assumed throughout the paper, see (Schabes and Joshi, 1991) for an introduction. We assume that our de nition of TAG does not have the substitution operation. See (Aho et al., 1986) for details on LR parsing. The algorithm described here can be extended to use SLR(1) tables (Schabes and Vijay-Shanker, 1990). made by the parser can be explained by an automaton which is weakly equivalent to TAGs called Bottom-Up Embedded Pushdown Automata (BEPDA) (Schabes and Vijay-Shanker, 1990). Storage in a BEPDA is a sequence of stacks, where new stacks can be introduced above and below the top stack in the automaton. Recognition of adjunction is equivalent to the unwrap move shown in Fig. 1.