本文件通过概述SPA系统提供的架构和服务的基本原则，定义了SPA系统的构成。本文中定义的功能可向下延伸至各个SPA标准文件。

This document defines what constitutes a SPA system by outlining the basic principles of the architecture and the services that a SPA system provides. The capabilities defined herein flow-down to the individual SPA Standards documents.