Grammars working on layered strings
We consider first an operation with strings and languages suggested by superposed windows on the computer screen (as well as by cryptographic systems of Richelieu type): we assume that the strings contain usual symbols as well as a transparent symbol. Superposing two strings (justified to left), we...
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| Main Authors: | |
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| Format: | Article |
| Published: |
1998
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| Series: | Acta cybernetica
13 No. 4 |
| Kulcsszavak: | Számítástechnika, Kibernetika |
| Subjects: | |
| Online Access: | http://acta.bibl.u-szeged.hu/12595 |
| Summary: | We consider first an operation with strings and languages suggested by superposed windows on the computer screen (as well as by cryptographic systems of Richelieu type): we assume that the strings contain usual symbols as well as a transparent symbol. Superposing two strings (justified to left), we produce a new string consisting of the symbols observable from above. This operation is investigated as an abstract operation on strings, then it is used in building a variant of grammar systems with the component grammars working on the layers of an array of strings. Each grammar can rewrite only symbols in its layer which are observable from above. The language generated in this way consists of strings of the observable symbols, produced at the end of a derivation. The power of several variants of these generative mechanisms is investigated for the case of two layered strings. When a matrix-like control on the work of the component grammars is considered, then a characterization of recursively enumerable languages is obtained. |
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| Physical Description: | 339-358 |
| ISSN: | 0324-721X |