DTD-属性

 DTD里属性用ATTLIST声明

语法：

<!ATTLIST element-name attribute-name attribute-type default-value>

例：

<!ATTLIST payment type CDATA "check">

XML例：<payment type="check" />

attribute-type列表如下：

Type Description

CDATA

The value is character data

(en1|en2|..)

The value must be one from an enumerated list

ID

The value is a unique id

IDREF

The value is the id of another element

IDREFS

The value is a list of other ids

NMTOKEN

The value is a valid XML name

NMTOKENS

The value is a list of valid XML names

ENTITY

The value is an entity

ENTITIES

The value is a list of entities

NOTATION

The value is a name of a notation

xml:

The value is a predefined xml value

The default-value can be one of the following:

Value Explanation

value

The default value of the attribute

#REQUIRED

The attribute is required

#IMPLIED

The attribute is not required

#FIXED value

The attribute value is fixed

带默认属性值的

DTD:<!ELEMENT square EMPTY>

<!ATTLIST square width CDATA "0">

valid xml:<square width="100" />

属性必须有的：

语法：<!ATTLIST element-name attribute-name attribute-type #REQUIRED>

例：<!ATTLIST person number CDATA #REQUIRED>

有效的xml:<person number="5677" />

属性可有可无的

语法：<!ATTLIST element-name attribute-name attribute-type #IMPLIED>

例：DTD:<!ATTLIST contact fax CDATA #IMPLIED>

有效xml: <contact fax="555-667788" />  or  <contact />

固定属性的：

语法：<!ATTLIST element-name attribute-name attribute-type #FIXED "value">

例：DTD:<!ATTLIST sender company CDATA #FIXED "Microsoft">

有效xml:<sender company="Microsoft" />

带可选值属性的：

语法：<!ATTLIST element-name attribute-name (en1|en2|...)  default-value>

例：<!ATTLIST payment type (check|cash) "cash">

xml例： <payment type="check">