语言是研究人与人之间交际的抽象系统。

Language is an abstract system used for human communication.

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第一级包括性能对象，它是可以为物理设备建模，或者抽象系统中组件的单元。

The first level consists of the performance object, which is a unit that can model a physical device or abstract component in a system.

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作者建造的抽象系统仅仅存在于他的脑海里，它的物理表现(书)仅仅是为了方便的保存和发行的一种手段。

The abstract system that an author constructs exists only in his mind, and the physical manifestation — the book — is only a convenient means of storage and distribution.

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