Regulated pushdown automata

The present paper suggests a new investigation area of the formal language theory — regulated automata. Specifically, it investigates pushdown automata that regulate the use of their rules by control languages. It proves that this regulation has no effect on the power of pushdown automata if the control languages are regular. However, the pushdown automata regulated by linear control languages characterize the family of recursively enumerable languages. All these results are established in terms of (A) acceptance by final state, (B) acceptance by empty pushdown, and (C) acceptance by final state and empty pushdown. In its conclusion, this paper formulates several open problems

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

Parsing Based on Regulated Automata

Tato práce se zabývá návrhem, aplikovatelností v praxi a implementací metody syntaktické analýzy založené na zásobníkových automatech, které regulují použití jejich pravidel řídícím lineárním jazykem. Tyto automaty mají větší sílu než běžný zásobníkový automat a jejich síla je rovna Turingovému stroji. Jsou schopné akceptovat rodinu rekurzivně vyčíslitelných jazyků.This work deals with the design, applicability and the implementation of parsing methods based on pushdown automata that regulate the use of their rules by linear control languages. These automata are more powerful than ordinary automata and they are as powerful as Turing machine. The pushdown automata regulated by linear control languages characterize the family of recursively enumerable languages.

Self-regulating finite automata

This paper introduces and discusses self-regulating finite automata. In essence, these automata regulate the use of their rules by a sequence of rules applied during previous moves. A special attention is paid to turns defined as moves during which a self-regulating finite automaton starts a new self-regulating sequence of moves. Based on the number of turns, the present paper establishes two infinite hierarchies of language families resulting from two variants of these automata. In addition, it demonstrates that these hierarchies coincide with the hierarchies resulting from parallel right linear grammars and right linear simple matrix grammars, so the self-regulating finite automata can be viewed as the automaton counterparts to these grammars. Finally, this paper compares both infinite hierarchies. In addition, as an open problem area, it suggests the discussion of self-regulating pushdown automata and points out that they give rise to no infinite hierarchy analogical to the achieved hierarchies resulting from the self-regulating finite automata

Self-reproducing pushdown transducers

summary:After a translation of an input string, $x$, to an output string, $y$, a self- reproducing pushdown transducer can make a self-reproducing step during which it moves $y$ to its input tape and translates it again. In this self- reproducing way, it can repeat the translation $n$-times for any $n \ge 1$. This paper demonstrates that every recursively enumerable language can be characterized by the domain of the translation obtained from a self- reproducing pushdown transducer that repeats its translation no more than three times

Non-Returning Turing Machines

Tato práce zavádí omezenou variantu Turingových strojů, které se nemohou pohybovat doleva, tedy se vracet na pásce. Ostatní vlastnosti Turingových strojů (například potenciálně nekonečná páska a schopnost přepisovat symboly na pásce) jsou zachovány. Zavedením tohoto omezení limitujeme vyjadřovací sílu Turingových strojů do té míry, ľe Turingovy stroje bez návratu na pásce jsou ekvivalentní s konečnými automaty a lze je na konečný automat transformovat. Dále je představen a detailně popsán algoritmus, který realizuje tuto transformaci.This work introduces a restricted variant of the Turing machine which cannot move left, thus return on its tape. Other properties, such as the potentially infinite symbol tape or the ability to rewrite symbols on the tape, remain unchanged. By introducing this restriction we limit the expressive power of the Turing machine to the point, where a non-returning Turing machine is equivalent to a finite automaton and can be transformed into one. A transformation algorithm is presented and described in detail.

Regulated Formal Models and Their Reduction

Department of Theoretical Computer Science and Mathematical LogicKatedra teoretické informatiky a matematické logikyFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Transducer Systems

Tato práce zavádí systémy zásobníkových převodníků. Základní myšlenka vychází z kooperujících distribuovaných gramatických systémů, které umožňují práci více gramatik na jednom řetězci. Převodníky spolupracují předáváním výsledků svých překladů jako vstupu pro další komponentu. Dále tato práce zkoumá jejich popisnou sílu a ekvivalenci systémů s různými počty komponent. Hlavním závěrem je pak porovnání popisné síly s Turingovými stroji a to s ohledem na jimi definovaný překlad i přijímané jazyky.This document defines systems of pushdown transducers. The idea of cooperating distributed grammar systems for components working on one word is adjusted for use of transducers instead of grammars. The transducers cooperate by passing output of one to input of another component. It discusses their descriptive power and equivalency between systems with arbitrary numbers of components. The main conclusion is then comparison of their descriptive power with Turing machines with regard to their translation and accepted languages.