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Bisimulation equivalence is decidable in polynomial time over normed graphs generated by a context-free grammar. We present a new algorithm, working in time O(n 5), thus improving the previously known complexity O(n 8 polylog(n)). It also improves the previously known complexity O(n 6 polylog(n)) of the equality problem for simple grammars. 1 Introduction(More)
Bisimulation equivalence is decidable in polynomial time for both sequential and commutative normed context-free processes, known as BPA and BPP, respectively. Despite apparent similarity between the two classes, different techniques were used in each case. We provide one polynomial-time algorithm that works in a superclass of both normed BPA and BPP. It is(More)
When can two regular word languages K and L be separated by a simple language? We investigate this question and consider separation by piecewise-and suffix-testable languages and variants thereof. We give characterizations of when two languages can be separated and present an overview of when these problems can be decided in polynomial time if K and L are(More)
We investigate normed commutative context-free processes (Basic Parallel Processes). We show that branching bisimilarity admits the bounded response property: in the Bisimulation Game, Duplicator always has a response leading to a process of size linearly bounded with respect to the Spoiler’s process. The linear bound is effective, which leads to(More)
We investigate the complexity of deciding whether a given regular language can be defined with a deterministic regular expression. Our main technical result shows that the problem is PSPACE-complete if the input language is represented as a regular expression or nondeter-ministic finite automaton. The problem becomes EXPSPACE-complete if the language is(More)
This paper is about reachability analysis in a restricted subclass of multi-pushdown automata: we assume that the control states of an automaton are partially ordered, and all transitions of an automaton go downwards with respect to the order. We prove decidability of the reachability problem, and computability of the backward reachability set. As the main(More)
Author's declaration: aware of legal responsibility I hereby declare that I have written this dissertation myself and all the contents of the dissertation have been obtained by legal means. Abstract This thesis is about an extension of context-free grammars with partial commutation on nonterminal symbols. In particular, we investigate the subclass with(More)
Branching bisimilarity of nor med Basic Process Algebra (BPA) processes was shown to be decidable by Yuxi Fu (ICALP 2013) but his proof has not provided any upper complexity bound. We present a simpler approach based on relative prime decompositions that leads to a nondeterministic exponential-time algorithm, this is "close" to the known exponential-time(More)
Given two families of sets F and G, the F separability problem for G asks whether for two given sets U, V ∈ G there exists a set S ∈ F, such that U is included in S and V is disjoint with S. We consider two families of sets F: modular sets S ⊆ N d , defined as unions of equivalence classes modulo some natural number n ∈ N, and unary sets. Our main result is(More)