Abstract A word u= u_1\dots u_n is a scattered factor of a word w if u can be obtained from w
by deleting some of its letters: there exist the (potentially empty) words v_0, v_1,..\,, v_n such …

A word u is a subsequence of another word w if u can be obtained from w by deleting some
of its letters. In the early 1970s, Imre Simon defined the relation∼ _k (called now Simon …

Matching Patterns with Variables Under Simon’s Congruence | SpringerLink Skip to main
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In the emerging field of DNA storage, data is encoded as DNA sequences and stored. The
data is read out again by sequencing the stored DNA. Nanopore sequencing is a new …

We examine questions involving nondeterministic finite automata where all states are final,
initial, or both initial and final. First, we prove hardness results for the nonuniversality and …

In discrete event systems prone to unobservable faults, a diagnoser must eventually detect
fault occurrences. The diagnosability problem consists in deciding whether such a …

The downward closure of a language is the set of all (not necessarily contiguous) subwords
of its members. It is well-known that the downward closure of every language is regular …

Partially ordered NFAs (poNFAs) are NFAs where cycles occur only in the form of self-loops.
A poNFA is universal if it accepts all words over its alphabet. Deciding universality is PSpace …

Scattered factor (circular) universality was firstly introduced by Barker et al. in 2020. A word $
w $ is called $ k $-universal for some natural number $ k $, if every word of length $ k $ of …

We answer two open questions by (Gruber, Holzer, Kutrib, 2009) on the state-complexity of
representing sub-or superword closures of context-free grammars (CFGs):(1) We prove a …