TY  - JOUR
A1  - Bordihn, Henning
A1  - Vaszil, György
T1  - Reversible parallel communicating finite automata systems
JF  - Acta informatica
N2  - We study the concept of reversibility in connection with parallel communicating systems of finite automata (PCFA in short). We define the notion of reversibility in the case of PCFA (also covering the non-deterministic case) and discuss the relationship of the reversibility of the systems and the reversibility of its components. We show that a system can be reversible with non-reversible components, and the other way around, the reversibility of the components does not necessarily imply the reversibility of the system as a whole. We also investigate the computational power of deterministic centralized reversible PCFA. We show that these very simple types of PCFA (returning or non-returning) can recognize regular languages which cannot be accepted by reversible (deterministic) finite automata, and that they can even accept languages that are not context-free. We also separate the deterministic and non-deterministic variants in the case of systems with non-returning communication. We show that there are languages accepted by non-deterministic centralized PCFA, which cannot be recognized by any deterministic variant of the same type.
KW  - Finite automata
KW  - Reversibility
KW  - Systems of parallel communicating
KW  - automata
Y1  - 2021
U6  - https://doi.org/10.1007/s00236-021-00396-9
SN  - 0001-5903
SN  - 1432-0525
VL  - 58
IS  - 4
SP  - 263
EP  - 279
PB  - Springer
CY  - Berlin ; Heidelberg ; New York, NY
ER  - 
TY  - JOUR
A1  - Bordihn, Henning
A1  - Holzer, Markus
T1  - On the number of active states in finite automata
JF  - Acta informatica
N2  - We introduce a new measure of descriptional complexity on finite automata, called the number of active states. Roughly speaking, the number of active states of an automaton A on input w counts the number of different states visited during the most economic computation of the automaton A for the word w. This concept generalizes to finite automata and regular languages in a straightforward way. We show that the number of active states of both finite automata and regular languages is computable, even with respect to nondeterministic finite automata. We further compare the number of active states to related measures for regular languages. In particular, we show incomparability to the radius of regular languages and that the difference between the number of active states and the total number of states needed in finite automata for a regular language can be of exponential order.
Y1  - 2021
U6  - https://doi.org/10.1007/s00236-021-00397-8
SN  - 0001-5903
SN  - 1432-0525
VL  - 58
IS  - 4
SP  - 301
EP  - 318
PB  - Springer
CY  - Berlin ; Heidelberg [u.a.]
ER  -