An infinite hierarchy of language families generated by scattered context grammars with n-limited derivations
نویسندگان
چکیده
منابع مشابه
Leftmost Derivations of Propagating Scattered Context Grammars: A New Proof
Propagating scattered context grammars, introduced in [3], represent an important type of semi-parallel rewriting systems. Since their introduction, however, the exact relationship of the family of languages they generate to the family of context-sensitive languages is unknown. The language family generated by these grammars is included in the family of context-sensitive languages; on the other...
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A scattered context grammar, G, erases nonterminals in a k-limited way, where k≥ 1, if in every sentential form of any derivation, between every two symbols from which G derives non-empty strings, there occur no more than k nonterminals from which G derives empty words. This paper demonstrates that any scattered context grammar that erases nonterminals in this way can be converted to an equival...
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Recently, it has been shown that every recursively enumerable language can be generated by a scattered context grammar with no more than three nonterminals. However, in that construction, the maximal number of nonterminals simultaneously rewritten during a derivation step depends on many factors, such as the cardinality of the alphabet of the generated language and the structure of the generate...
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This paper contains more examples to formerly introduced concept of formal language equivalency. That is, for two models, there is a substitution by which we change each string of every yield sequence in one model so that sequence ofs string resulting from this change represents a yield sequence in the other equvalent model, these two models closely simulates each other; otherwise they do not. ...
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ژورنال
عنوان ژورنال: Theoretical Computer Science
سال: 2009
ISSN: 0304-3975
DOI: 10.1016/j.tcs.2008.12.013