The prefix is strictly a syntactic convenience; in general, it is not really a matter of XML language design but rather a matter of author or tool preference.
前缀完全是一种语法上的便利，一般而言实际上并不属于XML语言设计中的问题，仅仅是作者或者工具偏好的问题。
Language code hierarchies do not guarantee that all languages with a common prefix will be understood by those fluent in one or more of those languages.
语言代码层级并不保证拥有相同前缀的语言能够被它所描述的一个和多个语言流畅的理解。
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