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33
A discontinuity in pattern inference
 In Proceedings of the 21st Symposium on Theoretical Aspects of Computer Science, STACS 2004
, 2004
"... A discontinuity in pattern inference This item was submitted to Loughborough University’s Institutional Repository by the/an author. ..."
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Cited by 19 (11 self)
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A discontinuity in pattern inference This item was submitted to Loughborough University’s Institutional Repository by the/an author.
The Expressibility of Languages and Relations By Word Equations
, 1997
"... Classically, several properties and relations of words, such as "being a power of a same word", can be expressed by using word equations. This paper is devoted to study in general the expressive power of word equations. As main results we prove theorems which allow us to show that certain ..."
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Cited by 15 (6 self)
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Classically, several properties and relations of words, such as "being a power of a same word", can be expressed by using word equations. This paper is devoted to study in general the expressive power of word equations. As main results we prove theorems which allow us to show that certain properties of words are not expressible as components of solutions of word equations. In particular, "the primitiveness" and "the equal length" are such properties, as well as being "any word over a proper subalphabet".
A nonlearnable class of Epattern languages
 Theoretical Computer Science
, 2006
"... A nonlearnable class of Epattern languages This item was submitted to Loughborough University’s Institutional Repository by the/an author. ..."
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Cited by 11 (6 self)
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A nonlearnable class of Epattern languages This item was submitted to Loughborough University’s Institutional Repository by the/an author.
TwoVariable Word Equations
 in PSPACE, Proc. of FOCS
, 1999
"... We consider languages expressed by word equations in two variables and give a complete characterization for their complexity functions, that is, the functions that give the number of words of the same length. Specifically, we prove that there are only five types of complexities: constant, linear, ex ..."
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Cited by 7 (1 self)
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We consider languages expressed by word equations in two variables and give a complete characterization for their complexity functions, that is, the functions that give the number of words of the same length. Specifically, we prove that there are only five types of complexities: constant, linear, exponential, and two in between constant and linear. For the latter two, we give precise characterizations in terms of the number of solutions of Diophantine equations of certain types. In particular, we show that the linear upper bound on the nonexponential complexities by Karhumaki et al., cf. [KMP], is tight. There are several consequences of our study. First, we derive that both of the sets of all finite Sturmian words and of all finite Standard words are expressible by word equations. Second, we characterize the languages of nonexponential complexity which are expressible by twovariable word equations as finite unions of several simple parametric formulae and solutions of a twovariabl...
The unambiguity of segmented morphisms
 Discrete Applied Mathematics
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news on decision problems for patterns
 Information and Computation
"... Bad news on decision ..."
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On Extended Regular Expressions
"... Abstract. In this paper we extend the work of Campeanu, Salomaa and Yu [1] on extended regular expressions featured in the Unix utility egrep and the popular scripting language Perl. We settle the open issue of closure under intersection and provide an improved pumping lemma that will show that a la ..."
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Cited by 5 (0 self)
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Abstract. In this paper we extend the work of Campeanu, Salomaa and Yu [1] on extended regular expressions featured in the Unix utility egrep and the popular scripting language Perl. We settle the open issue of closure under intersection and provide an improved pumping lemma that will show that a larger class of languages is not recognizable by extended regular expressions. We also investigate some questions regarding extended multipattern languages introduced by Nagy in [2]. 1
Inclusion problems for patterns with a bounded number of variables
 In Proc. DLT 2010, volume 6224 of LNCS
, 2010
"... Abstract. We study the inclusion problems for pattern languages that are generated by patterns with a bounded number of variables. This continues the work by Freydenberger and Reidenbach (Information and Computation 208 (2010)) by showing that restricting the inclusion problem to significantly more ..."
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Cited by 4 (2 self)
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Abstract. We study the inclusion problems for pattern languages that are generated by patterns with a bounded number of variables. This continues the work by Freydenberger and Reidenbach (Information and Computation 208 (2010)) by showing that restricting the inclusion problem to significantly more restricted classes of patterns preserves undecidability, at least for comparatively large bounds. For smaller bounds, we prove the existence of classes of patterns with complicated inclusion relations, and an open inclusion problem, that are related to the Collatz Conjecture. In addition to this, we give the first proof of the undecidability of the inclusion problem for NEpattern languages that, in contrast to previous proofs, does not rely on the inclusion problem for Epattern languages, and proves the undecidability of the inclusion problem for NEpattern languages over binary and ternary alphabets. 1