Canonical Derivations in Programmed Grammars

V této práci jsou studovány kanonické derivace (se zaměřením na nejlevější derivace) v programovaných gramatikách a rozsah levého omezení. Je ukázáno, že zavedením n-limitovaných derivací v programovaných gramatikách tak, jako byly zavedeny pro stavové gramatiky, dostaneme nekonečnou hierarchii jazykových tříd vyplývající z n-limitovaných programovaných gramatik, takže rozsah levého omezení ovlivňuje generativní sílu n-limitovaných programovaných gramatik. Tento výsledek má význam pro syntaktickou analýzu založenou na programovaných gramatikách.This work studies canonical derivations (with focus on leftmost derivations) in programmed grammars and left restriction range. It is shown that if we introduce n-limited derivations in programmed grammars as they were defined for state grammars, we get an infinite hierarchy of language families resulting from n-limited programmed grammars, so the left restriction range affects the generative power of n-limited programmed grammars. This result is significant for syntactical analysis based on programmed grammars.

Rule-restricted Automaton-grammar transducers: Power and Linguistic Applications

This paper introduces the notion of a new transducer as a two-component system, which consists of a nite automaton and a context-free grammar. In essence, while the automaton reads its input string, the grammar produces its output string, and their cooperation is controlled by a set, which restricts the usage of their rules. From a theoretical viewpoint, the present paper discusses the power of this system working in an ordinary way as well as in a leftmost way. In addition, the paper introduces an appearance checking, which allows us to check whether some symbols are present in the rewritten string, and studies its e ect on the power. It achieves the following three main results. First, the system generates and accepts languages de ned by matrix grammars and partially blind multi-counter automata, respectively. Second, if we place a leftmost restriction on derivation in the context-free grammar, both accepting and generating power of the system is equal to generative power of context-free grammars. Third, the system with appearance checking can accept and generate all recursively enumerable languages. From more pragmatical viewpoint, this paper describes several linguistic applications. A special attention is paid to the Japanese-Czech translation

Prefix Restriction of Regulated Grammar Systems

Tato práce studuje gramatické systémy, jejichž komponenty používají pravidla, která mají na levé straně ne jeden neterminál, ale řetězec neterminálů. Práce u těchto gramatických systémů zavádí tři omezení derivace. První vyžaduje, aby k derivaci v každé větné formě došlo v rámci prvních l symbolů v prvním spojitém bloku neterminálů. Druhé omezení definuje derivaci pro větné formy, které obsahují nejvýše m spojitých bloků neterminálů. Třetí omezení rozšiřuje druhé o podmínku, že každý takový blok může být nejvýše délky h. Hlavním výsledkem této práce jsou důkazy o zmenšení generativní síly gramatických systémů u dvou z těchto omezení.This thesis studies grammar systems whose components use sequences of productions whose left-hand sides are formed by nonterminal strings, not just single nonterminals. It introduces three restrictions on the derivations in these grammar systems. The first restriction requires that all rewritten symbols occur within the first l symbols of the first continuous block of nonterminals in the sentential form during every derivation step. The second restriction defines derivations over sentential forms containing no more than m continuous blocks of nonterminals. The third restriction extends the second in the way that each sequence of nonterminals must be of length h or less. As its main result, the thesis demonstrates that two of these restrictions decrease the generative power of grammar systems.

Derivation in Scattered Context Grammar via Lazy Function Evaluation

This paper discusses scattered context grammars (SCG) and considers the application of scattered context grammar production rules. We use function that represents single derivation step over the given sentential form. Moreover, we define this function in such a way, so that it represents the delayed execution of scattered context grammar production rules using the same principles as a lazy evaluation in functional programming. Finally, we prove equivalence of the usual and the delayed execution of SCG production rules

On state-alternating context-free grammars

AbstractState-alternating context-free grammars are introduced, and the language classes obtained from them are compared to the classes of the Chomsky hierarchy as well as to some well-known complexity classes. In particular, state-alternating context-free grammars are compared to alternating context-free grammars (Theoret. Comput. Sci. 67 (1989) 75–85) and to alternating pushdown automata. Further, various derivation strategies are considered, and their influence on the expressive power of (state-) alternating context-free grammars is investigated

On three variants of rewriting P systems

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