requirement verification: ensures requirements are of sufficient quality to be able to begin construction

requirement validation: helps ensures that requirements provide business value and meet business need

primary and secondary actors are listed in the elements for user cases and scenarios, actors who participate in the use case in a supporting role are called secondary actors

conversion 转变; 转换; 转化; (宗教或信仰的) 改变; 皈依; 归附; (持球触地或持球越过对方球门线后的) 附加得分;