Principal由协议、域名以及端口三部分组成，在进程级别不同的组合之间互相隔离，它是整个系统的关键部分。

Key to system is the idea of a "principal", which in this case is the triple of protocol, domain-name, and port. Each combination is isolated from any other combination at the process level.

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(图6)选择端口，它可用作出站服务的一部分。

(Figure 6) Select the ports that are to be made available as part of the outbound service.

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第一部分定义了服务的抽象接口，用 端口类型（port type）表示，它包含 操作集合（也就是业务功能）。

The first defines the abstract interface of a service, represented by port types, which contain collections of operations (that is, business functions).

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