In 1993 , w . crawley - boevey introduced the conception of exceptional sequence to the representation theory of path algebra . he has shown that the braid group acts transitively on the set of complete exceptional sequence 1993年, w . crawley - boevey将例外序列的概念引入路代数的表示理论中,并证明了辫子群对路代数的模范畴中的完备例外序列的作用是可迁的。