A reference to a DTD or an XML Schema is possible for the XML documents.
A Simple XML Document:
Note.xml:
<?xml version="1.0"?> <note> <to>Sapna</to> <from>Tom</from> <heading>Message</heading> <body>Meeting on Monday at 11 AM.</body> </note> |
A DTD File:
Note.dtd:
<!ELEMENT note (to, from, heading, body)> <!ELEMENT to (#PCDATA)> <!ELEMENT from (#PCDATA)> <!ELEMENT heading (#PCDATA)> <!ELEMENT body (#PCDATA)> |
Explanation:
We are using the above DTD file to define the elements of the XML document note.xml. The four child elements: “to, from, heading, body” of the note element is defined in the first line. The type of the child elements: to, from, heading, body elements are defined as “#PCDATA”, in the line 2-5.
An XML Schema:
Note.xsd:
<?xml version="1.0"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="https://www.w3spoint.com" xmlns="https://www.w3spoint.com" elementFormDefault="qualified"> <xs:element name="note"> <xs:complexType> <xs:sequence> <xs:element name="to" type="xs:string"/> <xs:element name="from" type="xs:string"/> <xs:element name="heading" type="xs:string"/> <xs:element name="body" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element> </xs:schema> |
Explanation:
In the above example, we are using an XML Schema file to define the elements of the XML document “note.xml”. The note element contains other elements and is thus a complex type. The elements: to, from, heading, and body, do not contain other elements and are thus simple types.
A reference to a DTD:
A reference to a DTD is there for an XML document.
Example:
<?xml version="1.0"?> <!DOCTYPE note SYSTEM "https://www.w3spoint.com/xml/note.dtd"> <note> <to>Sapna</to> <from>Tom</from> <heading>Message</heading> <body>Meeting on Monday at 11 AM.</body> </note> |
A reference to an XML Schema:
A reference to an XML Schema is there for an XML document.
Example:
<?xml version="1.0"?> <note xmlns="https://www.codesjava.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://www.w3spoint.com/xml note.xsd"> <to>Sapna</to> <from>Tom</from> <heading>Message</heading> <body>Meeting on Monday at 11 AM.</body> </note> |