DTD modeling

Catalog

One 、 What is? XML?

Two 、XML The role of ?

3、 ... and 、 The standard XML Format

Four 、 Element definition

stay XML Join in DTD Statement

The classification of elements

The limitation of elements

Symbol of element restriction

The number of times an element appears

  5、 ... and 、 Attribute definitions

grammar

Attribute types type

Property description

If xml What to do if the document reports an error ？

---

One 、 What is? XML?

XML,Extensible Markup Language, Extensible markup language . The suffix of the file is ：.xml. It's like HTML Is used to display data ,XML Its function is to transmit and store data .

Two 、XML The role of ?

In order to facilitate different applications 、 Data sharing and communication between different platforms .

 

The functions of the specific points are ：

(1) It can be used as a simple database , Store and retrieve data ;

(2) Transfer files in the agreed format ;

(3) Make software configuration files .【 The configuration file ： Save the file of software settings 】

3、 ... and 、 The standard XML Format

1. Yes and There is only one root element
2. XML Label case Distinguish correctly
3. Use... Correctly End tag
4. correct Nested tag
5. Used Legal tag name
6. Definition Valid attributes

Four 、 Element definition

• stay XML Join in DTD Statement

<!DOCTYPE root[]>

• The classification of elements

<!ELEMENT element-name EMPTY>// Empty elements 
<!ELEMENT element-name (#PCDATA)>// Text elements 
<!ELEMENT element-name (e1,e2)>// Mixed elements 

• The limitation of elements

Symbol of element restriction

1. And ：(,)
2. Not ：(|)

The number of times an element appears

     0 or 1 Time ： ？

     0~N Time ： *

     1~N Time ： +

Example ：

  establish xml constraint , First, we have to analyze xml structure .
    1、 Root tag persons There are sub tags
    2、persons There are sub tags     Mix labels ( There are sub tags )
    3、person There are sub tags ：name、age、contact、br、 Mix labels ( There are sub tags )
    4、name,age No sub tags Mix labels ( There are sub tags )
    5、contact There are sub tags Mix labels ( There are sub tags )
    6、phone No sub tags , There are content , Text label

    7、email No sub tags , There are content , Text label
    8、br There are neither sub tags nor text content Empty label

  The code is as follows ：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE persons[
   <!ELEMENT persons (person+)>
   <!ELEMENT person (name,age,contact,br?)>
   <!ELEMENT name (#PCDATA)>
   <!ELEMENT age (#PCDATA)>
   <!ELEMENT contact (phone|email)>
   <!ELEMENT phone (#PCDATA)>
   <!ELEMENT email (#PCDATA)>
   <!ELEMENT br EMPTY>
]>
<persons>
	<person>
		<name> Zhang Xiaoming </name>
		<age>10</age>
		<contact>
			<phone>1234567</phone>
		</contact>
		<br/>
	</person>
	<person>
		<name> Zhang Daming </name>
		<age>35</age>
		<contact>
			<email>[email protected]</email>
		</contact>
	</person>
</persons>

---

  5、 ... and 、 Attribute definitions

• grammar

<!ATTLIST element-name att_name type desc>

• Attribute types type

ID

( male | Woman )

CDATA（ Text ）

IDREF（ quote ）

reference

• Property description

#REQUIRED: Required

#IMPLIED: Not required

‘ The default value is ’

Be careful ： Only type by  ( male | Woman ) Type ,desc Only by default

  Example

Attribute constraints

pid The attribute type is ID Required

sex The attribute type is the choice of men and women Default values can be set

qq The attribute type is text Not required

parent ( Quote a id) The attribute type is text Not required

  The code is as follows ：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE persons[
	<!ELEMENT persons (person+)>
	<!ELEMENT person (name,age,contact,br*)>
	<!ELEMENT name (#PCDATA)>
	<!ELEMENT age (#PCDATA)>
	<!ELEMENT contact (phone|email)>
    <!ELEMENT phone (#PCDATA)>
    <!ELEMENT email (#PCDATA)>
	<!ELEMENT br EMPTY>
	<!ATTLIST person
	    pid ID #REQUIRED
	    sex ( male | Woman ) ' male '
	    qq CDATA #IMPLIED
	    parent IDREF #IMPLIED
	    >
]>
<persons>
	<person pid="p1" sex=" male " qq="aaa" parent="p2">
		<name> Zhang Xiaoming </name>
		<age>10</age>
		<contact>
			<phone>1234567</phone>
		</contact>
		<br/>
	</person>
	<person pid="p2">
		<name> Zhang Daming </name>
		<age>35</age>
		<contact>
			<email>[email protected]</email>
		</contact>
	</person>
</persons>

When we don't fill in according to the constraint   It will cause an error Here's the picture

Be careful ： There should be a space between the element name and the attribute name ！！！

If xml What to do if the document reports an error ？

Window ==> Preferences ==>Validation Then check （ The default is select all ）, Finally, the application closes . Be careful ： Restart after setting eclipse