Theoretical Computer Science

A contextual net is a Petri net extended with read arcs, which allows transitions to check for tokens without consuming them. Contextual nets allow for better modelling of concurrent read access than Petri nets, and their unfoldings can be exponentially ...

We study the size-cost of Boolean operations on constant height deterministic pushdown automata, i.e., on the traditional pushdown automata with a built-in constant limit on the height of the pushdown. We design a simulation showing that a complement ...

The syntactic complexity of a regular language is the cardinality of its syntactic semigroup. The syntactic complexity of a subclass of the class of regular languages is the maximal syntactic complexity of languages in that class, taken as a function of ...

Given an arbitrarily large alphabet @S, we consider the family of regular languages over @S for which the deterministic minimal automaton has a strongly connected state diagram. We present a new method for checking whether such a language is semi-...

In this paper, we study the power of external contextual grammars with selection languages from subfamilies of the family of regular languages. If we consider families F"n which are obtained by restriction to n states or nonterminals or productions or ...

Motivated by applications to verification problems in string manipulating programs, we look at the problem of whether the heads in a multi-tape automaton are synchronized. Given an n-tape pushdown automaton M with a one-way read-only head per tape and a ...

We present binary deterministic finite automata of n states that meet the upper bound 2^n on the state complexity of reversal. The automata have a single final state and are one-cycle-free-path automata; thus the witness languages are deterministic ...

A transition is unobservable if it is labeled by a symbol removed by a projection. The present paper investigates a new structural property of incomplete deterministic finite automata-a number of states incident with an unobservable transition-and its ...

The paper determines the number of states in two-way deterministic finite automata (2DFA) over a one-letter alphabet sufficient and in the worst case necessary to represent the results of basic language-theoretic operations on 2DFAs with a certain ...

Two-way nondeterministic pushdown automata (2PDA) are classical nondeterministic pushdown automata (PDA) enhanced with two-way motion of the input head. In this paper, the subclass of 2PDA accepting bounded languages and making at most a constant number ...

A tree controlled grammar is specified as a pair (G,G^') where G is a context-free grammar and G^' is a regular grammar. Its language consists of all terminal words with a derivation in G such that all levels of the corresponding derivation tree-except ...