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SeriesParallel Automata and Short Regular Expressions
, 2009
"... Computing short regular expressions equivalent to a given finite automaton is a hard task. In this work we present a class of acyclic automata for which it is possible to obtain in time O(n² log n) an equivalent regular expression of size O(n). A characterisation of this class is made using propert ..."
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Computing short regular expressions equivalent to a given finite automaton is a hard task. In this work we present a class of acyclic automata for which it is possible to obtain in time O(n² log n) an equivalent regular expression of size O(n). A characterisation of this class is made using properties of the underlying digraphs that correspond to the seriesparallel digraphs class. Using this characterisation we present an algorithm for the generation of automata of this class and an enumerative formula for the underlying digraphs with a given number of vertices.
A Provenance Framework for DataDependent Process Analysis ∗
"... A datadependent process (DDP) models an application whose control flow is guided by a finite state machine, as well as by the state of an underlying database. DDPs are commonly found e.g., in ecommerce. In this paper we develop a framework supporting the use of provenance in static (temporal) anal ..."
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A datadependent process (DDP) models an application whose control flow is guided by a finite state machine, as well as by the state of an underlying database. DDPs are commonly found e.g., in ecommerce. In this paper we develop a framework supporting the use of provenance in static (temporal) analysis of possible DDP executions. Using provenance support, analysts can interactively test and explore the effect of hypothetical modifications to a DDP’s state machine and/or to the underlying database. They can also extend the analysis to incorporate the propagation of annotations from metadomains of interest, e.g., cost or access privileges. Toward this goal we note that the framework of semiringbased provenance was proven highly effective in fulfilling similar needs in the context of database queries. In this paper we consider novel constructions that generalize the semiring approach to the context of DDP analysis. These constructions address two interacting new challenges: (1) to combine provenance annotations for both information that resides in the database and information about external inputs (e.g., user choices), and (2) to finitely capture infinite process executions. We analyze our solution from theoretical and experimental perspectives, proving its effectiveness. 1.
Simpleregular expressions and languages
 In Proceedings of DCFS’05, 146–157
, 2005
"... We define simpleregular expressions and languages. Simpleregular languages provide a necessary condition for a language to be outfixfree. We design algorithms that compute simpleregular languages from finitestate automata. Furthermore, we investigate the complexity blowup from a given finitest ..."
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We define simpleregular expressions and languages. Simpleregular languages provide a necessary condition for a language to be outfixfree. We design algorithms that compute simpleregular languages from finitestate automata. Furthermore, we investigate the complexity blowup from a given finitestate automaton to its simpleregular language automaton and show that there is an exponential blowup. In addition, we present a finitestate automata construction for simpleregular expressions based on state expansion. 1
IOS Press Intercode Regular Languages ∗
"... Abstract. Intercodes are a generalization of commafree codes. Using the structural properties of finitestate automata recognizing an intercode we develop a polynomialtime algorithm for determining whether or not a given regular language L is an intercode. If the answer is yes, our algorithm yield ..."
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Abstract. Intercodes are a generalization of commafree codes. Using the structural properties of finitestate automata recognizing an intercode we develop a polynomialtime algorithm for determining whether or not a given regular language L is an intercode. If the answer is yes, our algorithm yields also the smallest index k such that L is a kintercode. Furthermore, we examine the prime intercode decomposition of intercode regular languages and design an algorithm for the intercode primality test of an intercode recognized by a finitestate automaton. We also propose an algorithm that computes the prime intercode decomposition of an intercode regular language in polynomial time. Finally, we demonstrate that the prime intercode decomposition need not be unique.
Regular Languagesusing StatePair Graphs
"... We survey recent results on decision algorithms for subfamilies of regular languages. In particular, we look at the decision algorithms using statepair graphs constructed from finitestate automata. The algorithms rely on the structural property of a finitestate automaton that is preserved in its s ..."
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We survey recent results on decision algorithms for subfamilies of regular languages. In particular, we look at the decision algorithms using statepair graphs constructed from finitestate automata. The algorithms rely on the structural property of a finitestate automaton that is preserved in its statepair graph. We also review applications of statepair graphs in different subfamilies of regular languages. ∗ Han was supported by the KIST Tangible Space Initiative Grants 2E20050 and 2Z03050. The Bulletin of the EATCS 1