许多控制语言使用一个术语层次结构，这些术语的范围涵盖从更一般级别到更特定级别的描述。

Many controlled languages use a hierarchy of terms that go from a more general level of description to a more specific level.

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XML 在一个层次结构中表示信息，该结构的元素和属性一般用可读性很强的语言编写。

XML presents information in a hierarchical structure with elements and attributes usually written in easy-to-read language.

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象Haskell那样的纯函数型语言可以提供类型层次结构、区别合并、量化、存在类型等等，但OOP语言通常缺乏这些功能。

A pure functional language like Haskell might offer type hierarchies, discriminated unions, quantification, existential types, and so on, but OOP languages typically lack these things.

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