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Documents authored by Gulan, Stefan


Document
Graphs Encoded by Regular Expressions

Authors: Stefan Gulan

Published in: LIPIcs, Volume 9, 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011)


Abstract
In the conversion of finite automata to regular expressions, an exponential blowup in size can generally not be avoided. This is due to graph-structural properties of automata which cannot be directly encoded by regular expressions and cause the blowup combinatorially. In order to identify these structures, we generalize the class of arc-series-parallel digraphs to the acyclic case. The resulting digraphs are shown to be reversibly encoded by linear-sized regular expressions. We further derive a characterization of our new class by a finite set of forbidden minors and argue that these minors constitute the primitives causing the blowup in the conversion from automata to expressions.

Cite as

Stefan Gulan. Graphs Encoded by Regular Expressions. In 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011). Leibniz International Proceedings in Informatics (LIPIcs), Volume 9, pp. 495-506, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2011)


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@InProceedings{gulan:LIPIcs.STACS.2011.495,
  author =	{Gulan, Stefan},
  title =	{{Graphs Encoded by Regular Expressions}},
  booktitle =	{28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011)},
  pages =	{495--506},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-25-5},
  ISSN =	{1868-8969},
  year =	{2011},
  volume =	{9},
  editor =	{Schwentick, Thomas and D\"{u}rr, Christoph},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2011.495},
  URN =		{urn:nbn:de:0030-drops-30386},
  doi =		{10.4230/LIPIcs.STACS.2011.495},
  annote =	{Keywords: Digraphs, Regular Expressions, Finite Automata, Forbidden Minors}
}
Document
An Optimal Construction of Finite Automata from Regular Expressions

Authors: Stefan Gulan and Henning Fernau

Published in: LIPIcs, Volume 2, IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (2008)


Abstract
We consider the construction of finite automata from their corresponding regular expressions by a series of digraph-transformations along the expression\'s structure. Each intermediate graph represents an extended finite automaton accepting the same language. The character of our construction allows a fine-grained analysis of the emerging automaton\'s size, eventually leading to an optimality result.

Cite as

Stefan Gulan and Henning Fernau. An Optimal Construction of Finite Automata from Regular Expressions. In IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science. Leibniz International Proceedings in Informatics (LIPIcs), Volume 2, pp. 211-222, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2008)


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@InProceedings{gulan_et_al:LIPIcs.FSTTCS.2008.1754,
  author =	{Gulan, Stefan and Fernau, Henning},
  title =	{{An Optimal Construction of Finite Automata from Regular Expressions}},
  booktitle =	{IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science},
  pages =	{211--222},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-08-8},
  ISSN =	{1868-8969},
  year =	{2008},
  volume =	{2},
  editor =	{Hariharan, Ramesh and Mukund, Madhavan and Vinay, V},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2008.1754},
  URN =		{urn:nbn:de:0030-drops-17544},
  doi =		{10.4230/LIPIcs.FSTTCS.2008.1754},
  annote =	{Keywords: Finite automata,regular expressions,descriptional complexity}
}
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