XML — Schema

What is XSD?

XML Schema Definition (XSD) defines the structure and data types of XML documents.

Basic Schema

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:element name="book">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="title" type="xs:string"/>
                <xs:element name="author" type="xs:string"/>
                <xs:element name="price" type="xs:decimal"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

Data Types

Type	Description
xs:string	Text
xs:integer	Whole number
xs:decimal	Decimal number
xs:boolean	true/false
xs:date	Date
xs:dateTime	Date and time

Restrictions

<xs:element name="age">
    <xs:simpleType>
        <xs:restriction base="xs:integer">
            <xs:minInclusive value="0"/>
            <xs:maxInclusive value="120"/>
        </xs:restriction>
    </xs:simpleType>
</xs:element>

Occurrence

<xs:element name="book" maxOccurs="unbounded"/>
<xs:element name="subtitle" minOccurs="0"/>

Referencing a Schema

<book xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="book.xsd">

Mini Practice

1. Create a basic XSD
2. Use different data types
3. Add restrictions and constraints
4. Validate XML against the schema

Up Next

Continue with Parser — parsing XML documents.