为什么这不是有效的XML DTD? (参数实体和#PCDATA)

时间:2023-01-15 19:17:02

Using the DTD validator here, I am informed that the following DTD is invalid.

在这里使用DTD验证器,我被告知以下DTD无效。

<!ENTITY % text "(#PCDATA|L)*">
<!ELEMENT H         (%text;)+>
<!ELEMENT L         (#PCDATA)>

The error message is: "A '(' character or an element type is required within declaration of element type "H"." at line 2, column 22.

错误消息是:“A'('字符或元素类型在元素类型”H“的声明中是必需的。”在第2行第22列。

Can anyone please point out why it is invalid? And how can I make it valid? The error message is not exactly very friendly to me. Thanks.

谁能指出为什么它无效?我怎样才能使它有效?错误消息对我来说并不是非常友好。谢谢。

1 个解决方案

#1


8  

You cannot enforce that an element with mixed content must have at least one child node. Your DTD becomes

您无法强制具有混合内容的元素必须至少具有一个子节点。你的DTD变成了

<!ELEMENT H         ((#PCDATA|L)*)+>

when the entity is expanded. The only allowed form for elements with mixed content is

当实体扩展时。具有混合内容的元素唯一允许的形式是

(#PCDATA | A | B | C)*

where A, B and C are possible child elements. #PCDATA must be the first choice and the set must be allowed to repeat 0-infinity times, i.e. the asterisk is required.

其中A,B和C是可能的子元素。 #PCDATA必须是第一选择,并且必须允许该组重复0-infinity次,即需要星号。

#1


8  

You cannot enforce that an element with mixed content must have at least one child node. Your DTD becomes

您无法强制具有混合内容的元素必须至少具有一个子节点。你的DTD变成了

<!ELEMENT H         ((#PCDATA|L)*)+>

when the entity is expanded. The only allowed form for elements with mixed content is

当实体扩展时。具有混合内容的元素唯一允许的形式是

(#PCDATA | A | B | C)*

where A, B and C are possible child elements. #PCDATA must be the first choice and the set must be allowed to repeat 0-infinity times, i.e. the asterisk is required.

其中A,B和C是可能的子元素。 #PCDATA必须是第一选择,并且必须允许该组重复0-infinity次,即需要星号。