A note on exponential density of ETOL languages
Self-reproducing pushdown transducers
After a translation of an input string, , to an output string, , a self- reproducing pushdown transducer can make a self-reproducing step during which it moves to its input tape and translates it again. In this self- reproducing way, it can repeat the translation -times for any . 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...
Multigenerative grammar systems and matrix grammars
Multigenerative grammar systems are based on cooperating context-free grammatical components that simultaneously generate their strings in a rule-controlled or nonterminal-controlled rewriting way, and after this simultaneous generation is completed, all the generated terminal strings are combined together by some common string operations, such as concatenation, and placed into the generated languages of these systems. The present paper proves that these systems are equivalent with the matrix grammars....
Tree-controlled grammars with restrictions placed upon cuts and paths
First, this paper discusses tree-controlled grammars with root-to-leaf derivation-tree paths restricted by control languages. It demonstrates that if the control languages are regular, these grammars generate the family of context-free languages. Then, in a similar way, the paper introduces tree-controlled grammars with derivation-tree cuts restricted by control languages. It proves that if the cuts are restricted by regular languages, these grammars generate the family of recursively enumerable...
On context-free rewriting with a simple restriction and its computational completeness
This paper discusses context-free rewriting systems in which there exist two disjoint finite sets of rules, and a symbol, referred to as a condition of applicability, is attached to each rule in either of these two sets. In one set, a rule with a symbol attached to it is applicable if the attached symbol occurs in the current rewritten string while in the other set, such a rule is applicable if the attached symbol does not occur there. The present paper demonstrates that these rewriting systems...
Alan Mathison Turing – život a dílo
Automata with two-sided pushdowns defined over free groups generated by reduced alphabets
This paper introduces and discusses a modification of pushdown automata. This modification is based on two-sided pushdowns into which symbols are pushed from both ends. These pushdowns are defined over free groups, not free monoids, and they can be shortened only by the standard group reduction. We demonstrate that these automata characterize the family of recursively enumerable languages even if the free groups are generated by no more than four symbols.
Multi-island finite automata and their even computation
This paper discusses -island finite automata whose transition graphs can be expressed as -member sequences of islands , where there is a bridge leaving and entering for each . It concentrates its attention on even computation defined as any sequence of moves during which these automata make the same number of moves in each of the islands. Under the assumption that these automata work only in an evenly computational way, the paper proves its main result stating that -island finite automata...
Syntactic complexity of regulated rewriting
Page 1