A Relation Between Unambiguous Regular Expressions and Data Types
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Regular Expressions into Finite Automata
It is a well-established fact that each regular expression can be transformed into a non-deterministic nite automaton (NFA) with or without-transitions, and all authors seem to provide their own variant of the construction. Of these, Berry and Sethi 4] have shown that the construction of an-free NFA due to Glushkov 10] is a natural representation of the regular expression, because it can be des...
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The ISO standard for the Standard Generalized Markup Language (SGML) provides a syntactic meta-language for the definition of textual markup systems. In the standard, the right-hand sides of productions are based on regular expressions, although only regular expressions that denote words unambiguously, in the sense of the ISO standard, are allowed. In general, a word that is denoted by a regula...
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In the Standard Generalized Markup Language (SGML), document types are deened by context-free grammars in an extended Backus-Naur form. The right-hand side of a production is called a content model. Content models are extended regular expressions that have to be unambiguous in the sense that \an element : : : that occurs in the document instance must be able to satisfy only one primitive conten...
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We consider the property of unambiguity for regular expressions, extended by an additional operator &. This denotes concatenation in any order, and must have arbitrary arity since it is not associative. This extension gives us high succinctness in expressing equivalent regular expressions without &. The property of unambiguity means for a regular expression e, that a symbol in a word from its l...
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We introduce the notions of blocked, block-marked and block-deterministic regular expressions. We characterize block-deterministic regular expressions with determin-istic Glushkov block automata. The results can be viewed as a generalization of the characterization of one-unambiguous regular expressions with deterministic Glushkov automata. In addition, when a language L has a block-determinist...
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