The definitions of 3A (Any time, Any place and Any device) utilization mode are presented and a formal model of user and service grid system (USG) is built using ASM.

• 给出了用户3A (Anytime, Anyplace and on Anydevice)使用模式的定义,利用抽象状态机(ASM)理论对用户和服务网格系统进行形式化建模,并证明了服务网格3A使用模式定理。