# On a classification of context-free languages

@article{Gruska1967OnAC, title={On a classification of context-free languages}, author={Jozef Gruska}, journal={Kybernetika}, year={1967}, volume={3}, pages={22-29} }

The set E of strings is said to be definable (strongly definable) if there is a context-free grammar G such that E is the set of all terminal strings generated from the initial symbol (from all non terminal symbols) of G. The classification of definable and strongly definable sets in dependence on minimal number of nonterminal symbols needed for their generation is given.

## 40 Citations

Syntactic complexity of context-free grammars over word monoids

- Computer Science, LinguisticsActa Informatica
- 2009

It is demonstrated that every recursively enumerable language can be defined by a ten-nonterminal context-free grammar over a word monoid generated by an alphabet and six words of length two.

Nonterminal complexity of some families of infinite regular languages

- Computer Science, LinguisticsArXiv
- 2021

This paper studies nonterminal complexity of some families of infinite regular languages, which can be computed for different families of regular languages.

On Descriptions of Context-Free Languages by CD Grammar Systems

- Computer ScienceDCFS
- 2001

It is proved that CD grammar systems can reach the best possible increase of efficiency compared with context-free grammars in all standard derivation modes with respect to both measures.

Descriptional Complexity of Context-Free Grammar Forms

- Linguistics, Computer ScienceTheor. Comput. Sci.
- 1993

Subregularly controlled derivations: restrictions by syntactic parameters

- MathematicsWhere Mathematics, Computer Science, Linguistics and Biology Meet
- 2001

This work considers regularly controlled context-free grammars and restricts the number of nonterminals or productions which are necessary to generate the regular control language and compares the succinctness of the description of regular languages by regular Grammars (without control) and regular grammar with regular control.

Six nonterminals are enough for generating each r.e. language by a matrix grammar

- Computer Science, Linguistics
- 1984

It is proved that each recursively enumerable language can be generated by a context-free matrix grammar with appearance checking (using λ-rules) which contains at most: six nonterminal symbols, that…

Cover Complexity of Finite Languages

- Computer Science, LinguisticsDCFS
- 2018

It is shown for a restricted class of context-free grammars that its grammatical cover complexity measure w.r.t. a finite language L is unbounded and that the cover complexity of L can be computed from the exact complexities of a finite number of covers.

On the size of context-free grammars

- Computer ScienceKybernetika
- 1972

One more criterion of complexity of CFG's, namely Symb (G) = = the number of all occurrences of all symbols in the rules of G, is defined and some results concerning the criteria Prod and Symb are derived.

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