XML - XML Schema

What is an XML Schema?

An XML Schema defines the structure, content, and data types of an XML document. It acts like a blueprint to ensure the XML data is valid and correctly formatted.

The most commonly used schema language is XSD (XML Schema Definition).

Schema is used for:

To validate XML documents
To enforce rules for elements and attributes
To specify data types (string, integer, date, etc.)
To ensure consistency and correctness across XML files

Basic XML Schema Syntax

Example XML File:

<?xml version="1.0"?>
<student xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="student.xsd">
  <name>Ravi</name>
  <age>21</age>
</student>

Corresponding XML Schema (`student.xsd`):

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
 <xs:element name="student">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="name" type="xs:string" />
        <xs:element name="age" type="xs:integer" />
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

Key Components of XML Schema:

Element	Description
`xs:schema`	Root element of the schema
`xs:element`	Defines an element (name, type)
`xs:complexType`	Groups nested elements
`xs:sequence`	Specifies order of child elements
`xs:attribute`	Defines attributes (name, type, use)
`xs:simpleType`	Defines basic data types or restrictions

Common XML Schema Data Types:

xs:string
xs:integer
xs:decimal
xs:boolean
xs:date
xs:time