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In mathematics (especially category theory), a multicategory is a generalization of the concept of category that allows morphisms of multiple arity. If morphisms in a category are viewed as analogous to functions, then morphisms in a multicategory are analogous to functions of several variables. == Definition == A multicategory consists of * a collection (often a proper class) of ''objects''; * for every finite sequence of objects (for von Neumann ordinal ) and object ''Y'', a set of ''morphisms'' from to ''Y''; and * for every object ''X'', a special identity morphism (with ''n'' = 1) from ''X'' to ''X''. Additionally, there are composition operations: Given a sequence of sequences of objects, a sequence of objects, and an object ''Z'': if * for each , ''f''''j'' is a morphism from to ''Y''''j''; and * ''g'' is a morphism from to ''Z'': then there is a composite morphism from to ''Z''. This must satisfy certain axioms: * If ''m'' = 1, ''Z'' = ''Y''0, and ''g'' is the identity morphism for ''Y''0, then ''g''(''f''0) = ''f''0; * if for each , ''n''''i'' = 1, , and ''f''''i'' is the identity morphism for ''Y''''i'', then ; and * an associativity condition: if for each and , is a morphism from , then are identical morphisms from to ''Z''. 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「Multicategory」の詳細全文を読む スポンサード リンク
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