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标题：Definite Clause Grammars with Parse Trees: Extension for Prolog
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作者：Falco Nogatz ; Dietmar Seipel ; Salvador Abreu 等
期刊名称：OASIcs : OpenAccess Series in Informatics
电子版ISSN：2190-6807
出版年度：2019
卷号：74
页码：1-14
DOI：10.4230/OASIcs.SLATE.2019.7
出版社：Schloss Dagstuhl -- Leibniz-Zentrum fuer Informatik
摘要：Definite Clause Grammars (DCGs) are a convenient way to specify possibly non-context-free grammars for natural and formal languages. They can be used to progressively build a parse tree as grammar rules are applied by providing an extra argument in the DCG rule's head. In the simplest way, this is a structure that contains the name of the used nonterminal. This extension of a DCG has been proposed for natural language processing in the past and can be done automatically in Prolog using term expansion. We extend this approach by a meta-nonterminal to specify optional and sequences of nonterminals, as these structures are common in grammars for formal, domain-specific languages. We specify a term expansion that represents these sequences as lists while preserving the grammar's ability to be used both for parsing and serialising, i.e. to create a parse tree by a given source code and vice-versa. We show that this mechanism can be used to lift grammars specified in extended Backus-Naur form (EBNF) to generate parse trees. As a case study, we present a parser for the Prolog programming language itself based only on the grammars given in the ISO Prolog standard which produces corresponding parse trees.
关键词：Definite Clause Grammar; Prolog; Term Expansion; Parse Tree; EBNF