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In computer science, in particular in the field of formal language theory, the term abstract family of languages refers to an abstract mathematical notion generalizing characteristics common to the regular languages, the context-free languages and the recursively enumerable languages, and other families of formal languages studied in the scientific literature. ==Formal definitions== A ''formal language'' is a set for which there exists a finite set of abstract symbols such that , where * is the Kleene star operation. A ''family of languages'' is an ordered pair , where # is an infinite set of symbols; # is a set of formal languages; # For each in there exists a finite subset ⊂ such that ⊆ ; and # ≠ Ø for some in . A ''trio'' is a family of languages closed under e-free homomorphism, inverse homomorphism, and intersection with regular language. A ''full trio,'' also called a ''cone,'' is a trio closed under arbitrary homomorphism. A ''(full) semi-AFL'' is a (full) trio closed under union. A ''(full) AFL'' is a ''(full) semi-AFL'' closed under concatenation and the Kleene plus. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「abstract family of languages」の詳細全文を読む スポンサード リンク
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