DTD - 实体(Entities)

分为内部实体与外部实体 

内部实体

语法

<!ENTITY entity-name "entity-value">

Example

DTD Example:

<!ENTITY writer "Donald Duck."><!ENTITY copyright "Copyright W3Schools.">

XML example:

<author>&writer;&copyright;</author>

注：实体分为三部分：&符 ，实体名字，分号；

外部实体

语法

<!ENTITY entity-name SYSTEM "URI/URL">

Example

DTD Example:

<!ENTITY writer SYSTEM "http://www.w3schools.com/entities.dtd"><!ENTITY copyright SYSTEM "http://www.w3schools.com/entities.dtd">

XML example:

<author>&writer;&copyright;</author>