Grammars with Scattered Nonterminals
نویسندگان
چکیده
منابع مشابه
Bounded Number of Parallel Productions in Scattered Context Grammars with Three Nonterminals
Scattered context grammars with three nonterminals are known to be computationally complete. So far, however, it was an open problem whether the number of parallel productions can be bounded along with three nonterminals. In this paper, we prove that every recursively enumerable language is generated by a scattered context grammar with three nonterminals and five parallel productions, each of w...
متن کاملTwo Power-Decreasing Derivation Restrictions in Generalized Scattered Context Grammars
The present paper introduces and discusses generalized scattered context grammars that are based upon sequences of productions whose left-hand sides are formed by nonterminal strings, not just single nonterminals. It places two restrictions on the derivations in these grammars. More specifically, let k be a positive integer. The first restriction requires that all rewritten symbols occur within...
متن کاملk-Limited Erasing Performed by Scattered Context Grammars
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...
متن کاملOn the descriptional complexity of scattered context grammars
This paper proves that every recursively enumerable language is generated by a scattered context grammar with no more than four nonterminals and three non-context-free productions. In its conclusion, it gives an overview of the results and open problems concerning scattered context grammars and languages.
متن کاملDescriptional Complexity of Three-Nonterminal Scattered Context Grammars: An Improvement
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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تاریخ انتشار 2002