请教863211,pjiang等大侠

请问你们对于AC21 same or similar occupational classification 有没有研究? 到底similar的定义是什么? 我看到 O'net上career cluster, 定义为"Career Clusters contain occupations in the same field of work that require similar skills." 不知道是不是指只要在同一个cluster 里的都是 same or similar 的 occupation 呢? 比如这个连接里的都算?(Science, Technology, Engineering and Mathematics)
http://online.onetcenter.org/find/career?c=15&g=Go