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...his preliminary version. 1 Introduction Recently, there has been a resurgence of interest in finite-state automata that allow more complex transition labels. In particular, Giammarresi and Montalbano =-=[4]-=- have studied generalized automata (introduced by Eilenberg [3]) with respect to determinism. Generalized automata have strings (or blocks) as transition labels rather than merely characters or the nu...

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... The advantage of prefix-free codes is that we can decode a given encoded string deterministically. Prefix-free regular languages have already been used to define determinism for generalized automata =-=[4]-=- and for expression automata [6]. Recently, Han et al. [5] considered prefix-free regular expressions as patterns in text searching and designed an efficient algorithm for the prefix-free regular-expr...

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...oper subfamily of codes, prefix-free regular languages are a proper subfamily of regular languages. Prefix-free regular languages have already been used to define determinism for generalized automata =-=[6]-=- and for expression automata [7]. The regular-expression matching problem has been well studied in the literature. Given a regular expression E and a text T ,Aho[1] showed that we can determine whethe...

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...nique and demonstrated the importance of prime prefix-free decomposition in practice. Prefix-free regular languages are often used in the literature: to define the determinism of generalized automata =-=[6]-=- and of expression automata [10], and to represent a pattern set [9]. ⋆ The authors were supported under the Research Grants Council of Hong Kong Competitive Earmarked Research Grant HKUST6197/01E. D....

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...; they allow regular languages on transitions instead of single characters. If we only allow characters on transitions, then A is an FA and if we only allow strings, then A is a generalized automaton =-=[4, 5]-=-. Since the strongly connected components of a directed graph can be computed in linear time [1], we can identify all orbits of A in linear time in |A|. Once we identify orbits, then we compute all si...

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...E-complete. Related work. We mention some related work: finite-state automata that allow more complex transition labels recently received a resurgence of attention. These include generalized automata =-=[7]-=- (a.k.a. string or lazy automata) with strings (or blocks) as transition labels rather than merely characters or the null string and expression automata [9], finite-state automata whose transition lab...

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...ix-free. 4.1 Prefix-free and suffix-free regular languages Prefix-freeness has already been used in the literature. Prefix-freeness defines Huffman codes [22] and determinism for generalized automata =-=[10]-=- and for expression automata [19]. Recently, Han et al. [16] considered prefix-free regular expressions as patterns in text searching and designed an efficient algorithm for the prefix-free regular-ex...