XML初学笔记(四)
【本文是在阅读http://www.w3school.com.cn/的教程时随手记下的内容,以免遗忘】
XML 验证
拥有正确语法的 XML 被称为"形式良好"的 XML。
通过某个 DTD 进行了验证的 XML 是"合法"的 XML。
形式良好的 XML 文档
一个"形式良好"的 XML 文档拥有正确的语法。
一个"形式良好"的 XML 文档会遵守前几章介绍过的 XML 语法规则:
- XML 文档必须有根元素
- XML 文档必须有关闭标签
- XML 标签对大小写敏感
- XML 元素必须被正确的嵌套
- XML 属性必须加引号
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验证 XML 文档
一个合法的 XML 文档是"形式良好"的 XML 文档,同样遵守文档类型定义 (DTD) 的语法规则:
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在上例中,DOCTYPE 声明是对外部 DTD 文件的引用。下面的段落展示了这个文件的内容。
XML DTD
DTD 的作用是定义 XML 文档的结构。它使用一系列合法的元素来定义文档结构:
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XML Schema
W3C 支持一种基于 XML 的 DTD 代替者,它名为 XML Schema:
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