Results 1  10
of
14
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 properties ..."
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Cited by 13 (5 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".
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 3 (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...
Pattern Languages versus Parallel Communicating Grammar Systems
, 1996
"... We compare the power of two (fairly different) recently investigated language identifying devices: patterns and parallel communicating (PC) grammar systems. The simulation of multipatterns by contextfree PC grammar systems is rather obvious, but, unexpectedly, this can be realized also by (noncen ..."
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Cited by 2 (0 self)
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We compare the power of two (fairly different) recently investigated language identifying devices: patterns and parallel communicating (PC) grammar systems. The simulation of multipatterns by contextfree PC grammar systems is rather obvious, but, unexpectedly, this can be realized also by (noncentralized) PC grammar systems with rightlinear components. Moreover, infinite multipatterns forming a regular set can also be simulated by PC grammar systems with rightlinear components, whereas PC grammar systems with contextfree components can simulate contextfree multipatterns with contextfree domains for variables. TUCS Research Group Mathematical Structures of Computer Science 1 Introduction The aim of this paper is to compare (the power of) two language identifying devices which were recently investigated in rather different contexts: patterns and parallel communicating (PC) grammar systems. We consider here a pattern in the sense of [2], as a string of terminal symbols and ...
Patterns
 EATCS Bulletin
, 2003
"... We review topics on formal language aspects of patterns. The main results on the equivalence and inclusion problems are presented. We discuss open problems, in particular, concerning pattern language decision problems and ambiguity in patterns. ..."
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Cited by 1 (0 self)
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We review topics on formal language aspects of patterns. The main results on the equivalence and inclusion problems are presented. We discuss open problems, in particular, concerning pattern language decision problems and ambiguity in patterns.
Generova'ni' vzor*u d^eleni' slov v UNICODE. V Kasprzak a Sojka [12], strany 2332. 2. David Antos^ a Petr Sojka. Pattern Generation Revisited. V Pepping [19], strany 717. 3. David Antos^ a Petr Sojka. Generova'ni' vzor*u pomoci' knihovny PATLIB a progra
 Barbara Beeton. Hyphenation exception log. TUGboat, 5(1):15, kv^eten 1984. 5. Barbara Beeton. Hyphenation exception log. TUGboat, 6(3):121, listopad
, 1985
"... "Go forth and make masterpieces of hyphenation patterns... " ..."
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"Go forth and make masterpieces of hyphenation patterns... "
On the Expressibility of Languages By Word Equations With a Bounded Number of Variables
"... A language (resp. a relation) is expressible by a word equation e if it is defined as the set of all values of an unknown (resp. a set of unknowns) over all solutions of the equation e. We show first tools that a language or a relation is not expressible by using a certain number of auxiliary unknow ..."
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A language (resp. a relation) is expressible by a word equation e if it is defined as the set of all values of an unknown (resp. a set of unknowns) over all solutions of the equation e. We show first tools that a language or a relation is not expressible by using a certain number of auxiliary unknowns. As a consequence an infinite hierarchy  based on the number of auxiliary unknowns  of expressible language is established. Also a number of auxiliary unknowns to encode a boolean formula of word equations into a single equation or inequality is considered. Finally, two new tools to show the nonexpressibility in general are shown, and as a consequence, a gap theorem for expressible languages is obtained.
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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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
Parameterized Pattern Queries
, 2007
"... We introduce parameterized pattern queries as a new paradigm to extend traditional pattern expressions over sequence databases. A parameterized pattern is essentially
a string made of constant symbols or variables where variables can be matched against any symbol of the input string.
Parameterized ..."
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We introduce parameterized pattern queries as a new paradigm to extend traditional pattern expressions over sequence databases. A parameterized pattern is essentially
a string made of constant symbols or variables where variables can be matched against any symbol of the input string.
Parameterized patterns allow a concise and expressive definition of regular expressions that would be very complex to describe without variables. They can also
be used to express additional constraints, to “relax” pattern expressions by allowing
more freedom, and finally to cluster patterns in order to minimize the number of
symbols’ comparisons.
Parallel Grammars  A Phenomenology
"... The aim of this paper is at least twofold: − to give prospective PhD students in the area hints at where to start a promising research and − to supplement earlier reference lists on parallel grammars, trying to cover recent papers as well as “older” papers which were somehow neglected in other revi ..."
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The aim of this paper is at least twofold: − to give prospective PhD students in the area hints at where to start a promising research and − to supplement earlier reference lists on parallel grammars, trying to cover recent papers as well as “older” papers which were somehow neglected in other reviews. Together with the nowadays classical book on L systems by G. Rozenberg and A. Salomaa and with the articles on L systems in the “Handbook of Formal Languages,” researchers will be equipped with a hopefully comprehensive list of references and ideas around parallel grammars.