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HomeBackend DevelopmentXML/RSS TutorialXML entity references, annotations, naming rules


实体引用

在 XML 中,一些字符拥有特殊的意义。

如果你把字符 "

这样会产生 XML 错误:

<message>if salary </message>

为了避免这个错误,请用实体引用来代替 "

<message>if salary < 1000 then</message>

在 XML 中,有 5 个预定义的实体引用:

注释:在 XML 中,只有字符 "

XML 中的注释

在 XML 中编写注释的语法与 HTML 的语法很相似:

<!-- This is a comment -->

在 XML 中,空格会被保留

HTML 会把多个连续的空格字符裁减(合并)为一个:

HTML:	Hello           my name is David.
输出:	Hello my name is David.

在 XML 中,文档中的空格不会被删节。

XML 命名规则

XML 元素必须遵循以下命名规则:

  • 名称可以含字母、数字以及其他的字符

  • 名称不能以数字或者标点符号开始

  • 名称不能以字符 “xml”(或者 XML、Xml)开始

  • 名称不能包含空格

可使用任何名称,没有保留的字词。

最佳命名习惯

使名称具有描述性。使用下划线的名称也很不错。

名称应当比较简短,比如:,而不是:

避免 "-" 字符。如果您按照这样的方式进行命名:"first-name",一些软件会认为你需要提取第一个单词。

避免 "." 字符。如果您按照这样的方式进行命名:"first.name",一些软件会认为 "name" 是对象 "first" 的属性。

避免 ":" 字符。冒号会被转换为命名空间来使用(稍后介绍)。

XML 文档经常有一个对应的数据库,其中的字段会对应 XML 文档中的元素。有一个实用的经验,即使用数据库的名称规则来命名 XML 文档中的元素。

非英语的字母比如 éòá 也是合法的 XML 元素名,不过需要留意当软件开发商不支持这些字符时可能出现的问题。

以上就是XML  实体引用、注释、命名规则 的内容,更多相关内容请关注PHP中文网(www.php.cn)!

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