DTD - 实体

Entities are variables used to define shortcuts to common text.
实体是用于定义普通文本快捷方式的变量。

- Entity references are references to entities.
实体参数就是反映实体特征的参数。
- Entities can be declared internal, or external
实体可以声明为内部实体或外部实体。

---

Internal Entity Declaration
内部实体声明

Syntax: 

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

DTD Example:

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

XML example:

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

 

---

External Entity Declaration
外部实体声明

Syntax: 

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

DTD Example:

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

XML example:

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