An administrative domain exposes itself to other administrative domains through a type of logical element known as a borderelement.
管理域通过被称为边界元的一类逻辑单元使其自身展示在其他管理域的面前。
2
On sequence diagrams incoming and outgoing messages (A.K.A. interactions) for a sequence can be modeled by connecting the messages to the border of the frame element (as seen in Figure 2).
In addition to providing a visual border, the frame element also has an important functional use in diagrams depicting interactions, such as the sequence diagram.