Validation

DTD

What is DTD?

DTD defines the legal structure, elements, and attributes of an XML document. It acts as a blueprint to validate the XML document’s format and content.

Types of DTD

Internal DTD: Declared inside the XML document.
External DTD: Declared in a separate file and linked to the XML document.

Basic Syntax

Internal DTD:

<!DOCTYPE rootElement [
  <!ELEMENT rootElement (child1, child2)>
  <!ELEMENT child1 (#PCDATA)>
  <!ELEMENT child2 EMPTY>
  <!ATTLIST child1
    attributeName CDATA #REQUIRED>
]>

External DTD

<!DOCTYPE rootElement SYSTEM "filename.dtd">

Common DTD Declarations

Declaration

Description

<!ELEMENT>

Defines an element and its content model (elements, text, empty).

<!ATTLIST>

Defines attributes for elements.

<!ENTITY>

Defines entities (shortcuts for text or special characters).

Example (Internal DTD)

<!DOCTYPE note [
  <!ELEMENT note (to, from, heading, body)>
  <!ELEMENT to (#PCDATA)>
  <!ELEMENT from (#PCDATA)>
  <!ELEMENT heading (#PCDATA)>
  <!ELEMENT body (#PCDATA)>
]>
<note>
  <to>Alice</to>
  <from>Bob</from>
  <heading>Reminder</heading>
  <body>Meeting at 10 AM</body>
</note>

XML Schema (XSD)

What is XML Schema (XSD)?

XML Schema Definition (XSD) is a more powerful and flexible way to define the structure, content, and data types of an XML document compared to DTD. It supports namespaces, data types, and complex type definitions.

Basic Syntax

Declare schema and define elements

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <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>

Key Features

Supports simple types (string, integer, date, etc.) and complex types (elements with nested content).
Allows restriction, extension, and reusability of types.
Validates data types and structure.
Supports namespaces.

Example of Usage in XML Document

<?xml version="1.0" encoding="UTF-8"?>
<note xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="note.xsd">
  <to>Alice</to>
  <from>Bob</from>
  <heading>Reminder</heading>
  <body>Meeting at 10 AM</body>
</note>

Advantages over DTD

Feature

DTD

XML Schema (XSD)

Data types

Yes (string, int, date, etc.)

Namespaces

Limited

Full support

Syntax

Non-XML

XML-based

Extensibility

Limited

Supports complex structures

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Last updated 7 months ago

hashtagDTD

hashtagWhat is DTD?

hashtagTypes of DTD

hashtagBasic Syntax

hashtagInternal DTD:

hashtagExternal DTD

hashtagCommon DTD Declarations

hashtagExample (Internal DTD)

hashtagXML Schema (XSD)

hashtagWhat is XML Schema (XSD)?

hashtagBasic Syntax

hashtagKey Features

hashtagExample of Usage in XML Document

hashtagAdvantages over DTD

DTD

What is DTD?

Types of DTD

Basic Syntax

Internal DTD:

External DTD

Common DTD Declarations

Example (Internal DTD)

XML Schema (XSD)

What is XML Schema (XSD)?

Basic Syntax

Key Features

Example of Usage in XML Document

Advantages over DTD