A Shift First Strategy for Generalized LR Parsing

Yong-Seok LEE  Hideto TOMABECHI  Jun-ichi AOE  

IEICE TRANSACTIONS on Information and Systems   Vol.E77-D   No.10   pp.1162-1169
Publication Date: 1994/10/25
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Artificial Intelligence and Cognitive Science
shift-first grammar,  shift-first parsing,  pseudo parsing,  Interleaved parsing,  

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Tomita's parsing method (GLR) is a practical and successful parsing method for natural language. However, one difficulty in the GLR is that interleaved constraint processing of syntax and semantics in parallel is not trivial during parsing, because it uses the precompiled table for a fast real-time parsing. In this paper, we present a method which makes the GLR adaptable to interleaved parsing while making some limitation on its generality. For interleaved parsing, the conflicts of the LR parsing table must be resolved at the parse time. The shift-reduce conflict among the above conflicts is the most serious one for interleaved parsing because of the lack of knowledge for the conflict resolution at the parse time. Therefore, we concentrate on resolving a shift-reduce conflict by introducing a grammar which is called a shift-first LR (k) grammar. Our method for this is that the conflict resolution is delayed by the shift-first strategy which makes an unconditional choice of shift actions in the case of a shift-reduce conflict. Then, a delayed resolution that resolves the conflict, is made. Depending on the decision of the resolution, the pseudo parsing, which parses symbols in the LR parser stack, proceeds. Our experiments showed that our parser is efficient while attaining the interleaved parsing at real time.