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#### Complexity of Proper Prefix-Convex Regular Languages

(Springer, 2017-06-27)

A language L over an alphabet Σ is prefix-convex if, for any words x,y,z∈Σ∗, whenever x and xyz are in L, then so is xy. Prefix-convex languages include right-ideal, prefix-closed, and prefix-free languages, which were ...

#### Complexity of Left-Ideal, Suffix-Closed and Suffix-Free Regular Languages

(Springer, 2017-03-06)

A language L over an alphabet Σ is suffix-convex if, for any words x,y,z∈Σ∗, whenever z and xyz are in L, then so is yz. Suffix-convex languages include three special cases: left-ideal, suffix-closed, and suffix-free ...

#### Quotient Complexity of Ideal Languages

(Elsevier, 2013-01-28)

A language L over an alphabet Σ is a right (left) ideal if it satisfies L=LΣ∗ (L=Σ∗L). It is a two-sided ideal if L=Σ∗LΣ∗, and an all-sided ideal if L=Σ∗L, the shuffle of Σ∗ with L. Ideal languages are not only of interest ...

#### Complexity of Suffix-Free Regular Languages

(Elsevier, 2017-11-01)

We study various complexity properties of suffix-free regular languages. A sequence (Lk,Lk+1,…) of regular languages in some class, where n is the quotient complexity of Ln, is most complex if its languages Ln meet the ...

#### Unrestricted State Complexity Of Binary Operations On Regular And Ideal Languages

(Institut für Informatik, 2017-08-27)

We study the state complexity of binary operations on regular languages over diﬀerent alphabets. It is known that if L′m and Ln are languages of state complexities m and n, respectively, and restricted to the same alphabet, ...

#### Syntactic Complexity of Regular Ideals

(Springer, 2017-08-04)

The state complexity of a regular language is the number of states in a minimal deterministic finite automaton accepting the language. The syntactic complexity of a regular language is the cardinality of its syntactic ...

#### Syntactic Complexity of Suffix-Free Languages

(Elsevier, 2017-09-05)

We solve an open problem concerning syntactic complexity: We prove that the cardinality of the syntactic semigroup of a suffix-free language with n left quotients (that is, with state complexity n) is at most (n−1)n−2+n−2 ...

#### Theory Of Atomata

(Elsevier, 2014-06-19)

We show that every regular language defines a unique nondeterministic finite automaton (NFA), which we call "atomaton", whose states are the "atoms" of the language, that is, non-empty intersections of complemented or ...

#### Quotient Complexity Of Closed Languages

(Springer, 2014-02-01)

A language L is prefix-closed if, whenever a word w is in L, then every prefix of w is also in L. We define suffix-, factor-, and subword-closed languages in an analogous way, where by factor we mean contiguous subsequence, ...