@article{BordihnDassowHolzer2010,
  author    = {Bordihn, Henning and Dassow, Juergen and Holzer, Markus},
  title     = {Extending regular expressions with homomorphic replacement},
  issn      = {0988-3754},
  doi       = {10.1051/Ita/2010013},
  year      = {2010},
  abstract  = {We define H- and EH-expressions as extensions of regular expressions by adding homomorphic and iterated homomorphic replacement as new operations, resp. The definition is analogous to the extension given by Gruska in order to characterize context-free languages. We compare the families of languages obtained by these extensions with the families of regular, linear context-free, context-free, and EDT0L languages. Moreover, relations to language families based on patterns, multi-patterns, pattern expressions, H-systems and uniform substitutions are also investigated. Furthermore, we present their closure properties with respect to TRIO operations and discuss the decidability status and complexity of fixed and general membership, emptiness, and the equivalence problem.},
  language  = {en}
}
@article{BordihnHolzerKutrib2009,
  author    = {Bordihn, Henning and Holzer, Markus and Kutrib, Martin},
  title     = {Determination of finite automata accepting subregular languages},
  issn      = {0304-3975},
  doi       = {10.1016/j.tcs.2009.05.019},
  year      = {2009},
  abstract  = {We investigate the descriptional complexity of the nondeterministic finite automaton (NFA) to the deterministic finite automaton (DFA) conversion problem, for automata accepting subregular languages such as combinational languages, definite languages and variants thereof, (strictly) locally testable languages, star-free languages, ordered languages, prefix-, suffix-, and infix-closed languages, and prefix-, Suffix-, and infix-free languages. Most of the bounds for the conversion problem are shown to be tight ill the exact number of states, that is, the number is sufficient and necessary in the worst case. Otherwise tight bounds in order of magnitude are shown.},
  language  = {en}
}
@article{BenschBordihnHolzeretal.2009,
  author    = {Bensch, Suna and Bordihn, Henning and Holzer, Markus and Kutrib, Martin},
  title     = {On input-revolving deterministic and nondeterministic finite automata},
  issn      = {0890-5401},
  doi       = {10.1016/J.Ic.2009.03.002},
  year      = {2009},
  abstract  = {We introduce and investigate input-revolving finite automata, which are (nondeterministic) finite state automata with the additional ability to shift the remaining part of the input. Three different modes of shifting are considered, namely revolving to the left, revolving to the right, and circular-interchanging. We investigate the computational capacities of these three types of automata and their deterministic variants, comparing any of the six classes of automata with each other and with further classes of well-known automata. In particular, it is shown that nondeterminism is better than determinism, that is, for all three modes of shifting there is a language accepted by the nondeterministic model but not accepted by any deterministic automaton of the same type. Concerning the closure properties most of the deterministic language families studied are not closed under standard operations. For example, we show that the family of languages accepted by deterministic right-revolving finite automata is an anti-AFL which is not closed under reversal and intersection.},
  language  = {en}
}
@article{Bordihn2004,
  author    = {Bordihn, Henning},
  title     = {Context-freeness of the power of context-free languages is undecidable},
  issn      = {0304-3975},
  year      = {2004},
  abstract  = {The power of a language L is the set of all powers of the words in L. In this paper, the following decision problem is investigated. Given a context-free language L, is the power of L context-free? We show that this problem is decidable for languages over unary alphabets, but it is undecidable whenever languages over alphabets with at least two letters are considered. (C) 2003 Elsevier B.V. All rights reserved},
  language  = {en}
}
@article{BordihnHolzerKutrib2005,
  author    = {Bordihn, Henning and Holzer, Markus and Kutrib, Martin},
  title     = {Unsolvability levels of operation problems for subclasses of context-free languages},
  issn      = {0129-0541},
  year      = {2005},
  abstract  = {We investigate the operation problem for linear and deterministic context-free languages: Fix an operation on formal languages. Given linear (deterministic, respectively) context-free languages, is the application of this operation to the given languages still a linear (deterministic, respectively) context-free language? Besides the classical operations, for which the linear and deterministic context-free languages are not closed, we also consider the recently introduced root and power operation. We show non-semidecidability, to be more precise, we show completeness for the second level of the arithmetic hierarchy for all of the aforementioned operations, except for the power operation, if the underlying alphabet contains at least two letters. The result for the power opera, tion solves an open problem stated in Theoret. Comput. Sci. 314 (2004) 445-449},
  language  = {en}
}
@article{Bordihn2005,
  author    = {Bordihn, Henning},
  title     = {On the number of components in cooperating distributed grammar systems},
  issn      = {0304-3975},
  year      = {2005},
  abstract  = {It is proved that the number of components in context-free cooperating distributed (CD) grammar systems can be reduced to 3 when they are working in the so-called sf-mode of derivation, which is the cooperation protocol which has been considered first for CD grammar systems. In this derivation mode, a component continues the derivation until and unless there is a nonterminal in the sentential form which cannot be rewritten according to that component. Moreover, it is shown that CD grammar systems in sf-mode with only one component can generate only the context-free languages but they can generate non-context-free languages if two components are used. The sf-mode of derivation is compared with other well-known cooperation protocols with respect to the hierarchies induced by the number of components. (C) 2004 Elsevier B.V. All rights reserved},
  language  = {en}
}
@phdthesis{Bordihn2011,
  author    = {Bordihn, Henning},
  title     = {Contributions to the syntactical analysis beyond context-freeness},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-59719},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Parsability approaches of several grammar formalisms generating also non-context-free languages are explored. Chomsky grammars, Lindenmayer systems, grammars with controlled derivations, and grammar systems are treated. Formal properties of these mechanisms are investigated, when they are used as language acceptors. Furthermore, cooperating distributed grammar systems are restricted so that efficient deterministic parsing without backtracking becomes possible. For this class of grammar systems, the parsing algorithm is presented and the feature of leftmost derivations is investigated in detail.},
  language  = {en}
}