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XML Tutorial

XML HOME XML Introduction XML How to use XML Tree XML Syntax XML Elements XML Attributes XML Namespaces XML Display XML HttpRequest XML Parser XML DOM XML XPath XML XSLT XML XQuery XML XLink XML Validator XML DTD XML Schema XML Server XML Examples XML Quiz XML Certificate

XML AJAX

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XML DOM

DOM Introduction DOM Nodes DOM Accessing DOM Node Info DOM Node List DOM Traversing DOM Navigating DOM Get Values DOM Change Nodes DOM Remove Nodes DOM Replace Nodes DOM Create Nodes DOM Add Nodes DOM Clone Nodes DOM Examples

XPath Tutorial

XPath Introduction XPath Nodes XPath Syntax XPath Axes XPath Operators XPath Examples

XSLT Tutorial

XSLT Introduction XSL Languages XSLT Transform XSLT <template> XSLT <value-of> XSLT <for-each> XSLT <sort> XSLT <if> XSLT <choose> XSLT Apply XSLT on the Client XSLT on the Server XSLT Edit XML XSLT Examples

XQuery Tutorial

XQuery Introduction XQuery Example XQuery FLWOR XQuery HTML XQuery Terms XQuery Syntax XQuery Add XQuery Select XQuery Functions

XML DTD

DTD Introduction DTD Building Blocks DTD Elements DTD Attributes DTD Elements vs Attr DTD Entities DTD Examples

XSD Schema

XSD Introduction XSD How To XSD <schema> XSD Elements XSD Attributes XSD Restrictions XSD Complex Elements XSD Empty XSD Elements-only XSD Text-only XSD Mixed XSD Indicators XSD <any> XSD <anyAttribute> XSD Substitution XSD Example

XSD Data Types

XSD String XSD Date/Time XSD Numeric XSD Misc XSD Reference

Web Services

XML Services XML WSDL XML SOAP XML RDF XML RSS

References

DOM Node Types DOM Node DOM NodeList DOM NamedNodeMap DOM Document DOM Element DOM Attribute DOM Text DOM CDATA DOM Comment DOM XMLHttpRequest DOM Parser XSLT Elements XSLT/XPath Functions

XML Schema


An XML Schema describes the structure of an XML document, just like a DTD.

An XML document with correct syntax is called "Well Formed".

An XML document validated against an XML Schema is both "Well Formed" and "Valid".


XML Schema

XML Schema is an XML-based alternative to DTD:

<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>

The Schema above is interpreted like this:

  • <xs:element name="note"> defines the element called "note"
  • <xs:complexType> the "note" element is a complex type
  • <xs:sequence> the complex type is a sequence of elements
  • <xs:element name="to" type="xs:string"> the element "to" is of type string (text)
  • <xs:element name="from" type="xs:string"> the element "from" is of type string
  • <xs:element name="heading" type="xs:string"> the element "heading" is of type string
  • <xs:element name="body" type="xs:string"> the element "body" is of type string

XML Schemas are More Powerful than DTD

  • XML Schemas are written in XML
  • XML Schemas are extensible to additions
  • XML Schemas support data types
  • XML Schemas support namespaces


Why Use an XML Schema?

With XML Schema, your XML files can carry a description of its own format.

With XML Schema, independent groups of people can agree on a standard for interchanging data.

With XML Schema, you can verify data.


XML Schemas Support Data Types

One of the greatest strengths of XML Schemas is the support for data types:

  • It is easier to describe document content
  • It is easier to define restrictions on data
  • It is easier to validate the correctness of data
  • It is easier to convert data between different data types

XML Schemas use XML Syntax

Another great strength about XML Schemas is that they are written in XML:

  • You don't have to learn a new language
  • You can use your XML editor to edit your Schema files
  • You can use your XML parser to parse your Schema files
  • You can manipulate your Schemas with the XML DOM
  • You can transform your Schemas with XSLT

If you want to study XML Schema, please read our XML Schema Tutorial.