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In mathematics and theoretical computer science, a semiautomaton is a deterministic finite automaton having inputs but no output. It consists of a set ''Q'' of states, a set Σ called the input alphabet, and a function ''T'': ''Q'' × Σ → ''Q'' called the transition function. Associated to any semiautomaton is a monoid called the characteristic monoid, input monoid, transition monoid or transition system of the semiautomaton, which acts on the set of states ''Q''. This may be viewed either as an action of the free monoid of strings in the input alphabet Σ, or as the induced transformation semigroup of ''Q''. In older books like Clifford and Preston (1967) S-acts are called "operands". In category theory, semiautomata essentially are functors. ==Transformation semigroups and monoid acts== : (詳細はset ''Q'' (often called the "set of states") and a semigroup or monoid ''M'' of functions, or "transformations", mapping ''Q'' to itself. They are functions in the sense that every element ''m'' of ''M'' is a map . If ''s'' and ''t'' are two functions of the transformation semigroup, their semigroup product is defined as their function composition . Some authors regard "semigroup" and "monoid" as synonyms. Here a semigroup need not have an identity element; a monoid is a semigroup with an identity element (also called "unit"). Since the notion of functions acting on a set always includes the notion of an identity function, which when applied to the set does nothing, a transformation semigroup can be made into a monoid by adding the identity function. 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「Semiautomaton」の詳細全文を読む スポンサード リンク
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