它是使用XML模式定义语言编写的，描述了XML文档的内容结构和约束。

It is written in the XML Schema definition language to describe the structure and constrain the content of XML documents.

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可以使用Web服务定义语言(Web Service Definition Language, WSDL)文档实现可变性。

Web Service Definition Language (WSDL) documents can be used to implement variability.

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传统模式语言如文档类型定义（DTD）、W3C Schemas 和 RELAX NG 的严格性带来了脆弱性。

The rigidity of traditional schema languages like Document Type Definitions (DTDs), W3C Schemas, and RELAX NG causes fragility.

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