Indexed Grammars—An Extension of Context-Free Grammars
- 1 October 1968
- journal article
- Published by Association for Computing Machinery (ACM) in Journal of the ACM
- Vol. 15 (4) , 647-671
- https://doi.org/10.1145/321479.321488
Abstract
A new type of grammar for generating formal languages, called an indexed grammar, is presented. An indexed grammar is an extension of a context-free grammar, and the class of languages generated by indexed grammars has closure properties and decidability results similar to those for context-free languages. The class of languages generated by indexed grammars properly includes all context-free languages and is a proper subset of the class of context-sensitive languages. Several subclasses of indexed grammars generate interesting classes of languages.Keywords
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