XSD Data Types
Understanding built-in and custom data types in XML Schema
🔢 What are XSD Data Types?
XSD data types define what kind of data an element or attribute can contain. They ensure data validity and include built-in types like string, integer, date, and boolean.
<!-- Using data types -->
<xs:element name="age" type="xs:integer"/>
<xs:element name="name" type="xs:string"/>
Built-in Data Types
String Types
Text and character data
<xs:element name="text"
type="xs:string"/>Numeric Types
Integer and decimal numbers
<xs:element name="count"
type="xs:integer"/>Date/Time Types
Dates, times, and durations
<xs:element name="birthday"
type="xs:date"/>Boolean Type
True or false values
<xs:element name="active"
type="xs:boolean"/>🔹 String Data Types
String types handle text data with various formats and constraints. Use them for names, descriptions, and any textual content in your XML documents.
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<!-- Basic string -->
<xs:element name="name" type="xs:string"/>
<!-- Normalized string (no line breaks/tabs) -->
<xs:element name="address" type="xs:normalizedString"/>
<!-- Token (no extra whitespace) -->
<xs:element name="code" type="xs:token"/>
</xs:schema>
<!-- Valid XML -->
<name>John Doe</name>
<address>123 Main Street</address>
<code>ABC123</code>String Type Differences:
string: Allows all characters including whitespace
normalizedString: Replaces tabs/newlines with spaces
token: Removes leading/trailing spaces and collapses whitespace
🔹 Numeric Data Types
Numeric types handle different kinds of numbers from whole integers to precise decimals. Choose the appropriate type based on your data requirements.
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<!-- Integer (whole numbers) -->
<xs:element name="quantity" type="xs:integer"/>
<!-- Positive integer -->
<xs:element name="id" type="xs:positiveInteger"/>
<!-- Decimal (with fractions) -->
<xs:element name="price" type="xs:decimal"/>
<!-- Float (scientific notation) -->
<xs:element name="measurement" type="xs:float"/>
<!-- Double (larger range) -->
<xs:element name="distance" type="xs:double"/>
</xs:schema>
<!-- Valid XML -->
<quantity>100</quantity>
<id>42</id>
<price>19.99</price>
<measurement>3.14159</measurement>
<distance>1.5E8</distance>Numeric Type Variants:
- integer: ..., -2, -1, 0, 1, 2, ...
- positiveInteger: 1, 2, 3, ...
- negativeInteger: ..., -3, -2, -1
- nonNegativeInteger: 0, 1, 2, ...
- nonPositiveInteger: ..., -2, -1, 0
🔹 Date and Time Types
Date and time types handle temporal data with specific formats. These types ensure consistent date/time representation across your XML documents.
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<!-- Date (YYYY-MM-DD) -->
<xs:element name="birthDate" type="xs:date"/>
<!-- Time (HH:MM:SS) -->
<xs:element name="startTime" type="xs:time"/>
<!-- DateTime (YYYY-MM-DDTHH:MM:SS) -->
<xs:element name="timestamp" type="xs:dateTime"/>
<!-- Duration (PnYnMnDTnHnMnS) -->
<xs:element name="duration" type="xs:duration"/>
</xs:schema>
<!-- Valid XML -->
<birthDate>1990-05-15</birthDate>
<startTime>14:30:00</startTime>
<timestamp>2024-10-16T14:30:00</timestamp>
<duration>P1Y2M3DT4H5M6S</duration>Format Examples:
date: 2024-10-16
time: 14:30:00
dateTime: 2024-10-16T14:30:00
duration: P1Y2M (1 year, 2 months)
🔹 Boolean and Other Types
Additional data types for specific use cases including boolean values, binary data, and URIs:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<!-- Boolean (true/false or 1/0) -->
<xs:element name="isActive" type="xs:boolean"/>
<!-- anyURI (web addresses) -->
<xs:element name="website" type="xs:anyURI"/>
<!-- base64Binary (encoded binary data) -->
<xs:element name="image" type="xs:base64Binary"/>
<!-- hexBinary (hex encoded data) -->
<xs:element name="hash" type="xs:hexBinary"/>
</xs:schema>
<!-- Valid XML -->
<isActive>true</isActive>
<website>https://example.com</website>
<image>R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==</image>
<hash>48656C6C6F</hash>🔹 Custom Data Types
Create your own data types by restricting or extending built-in types. This allows you to define specific validation rules for your data.
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<!-- Custom age type (0-120) -->
<xs:simpleType name="AgeType">
<xs:restriction base="xs:integer">
<xs:minInclusive value="0"/>
<xs:maxInclusive value="120"/>
</xs:restriction>
</xs:simpleType>
<!-- Custom email type -->
<xs:simpleType name="EmailType">
<xs:restriction base="xs:string">
<xs:pattern value="[^@]+@[^@]+\.[^@]+"/>
</xs:restriction>
</xs:simpleType>
<!-- Custom status type (enumeration) -->
<xs:simpleType name="StatusType">
<xs:restriction base="xs:string">
<xs:enumeration value="active"/>
<xs:enumeration value="inactive"/>
<xs:enumeration value="pending"/>
</xs:restriction>
</xs:simpleType>
<!-- Using custom types -->
<xs:element name="age" type="AgeType"/>
<xs:element name="email" type="EmailType"/>
<xs:element name="status" type="StatusType"/>
</xs:schema>
<!-- Valid XML -->
<age>25</age>
<email>[email protected]</email>
<status>active</status>🔹 Complete Example: User Profile
A practical example using multiple data types:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="user">
<xs:complexType>
<xs:sequence>
<xs:element name="username" type="xs:string"/>
<xs:element name="email" type="xs:string"/>
<xs:element name="age" type="xs:positiveInteger"/>
<xs:element name="registrationDate" type="xs:date"/>
<xs:element name="isVerified" type="xs:boolean"/>
<xs:element name="balance" type="xs:decimal"/>
<xs:element name="website" type="xs:anyURI" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="id" type="xs:integer" use="required"/>
</xs:complexType>
</xs:element>
</xs:schema>
<!-- Valid XML -->
<user id="12345">
<username>johndoe</username>
<email>[email protected]</email>
<age>30</age>
<registrationDate>2024-01-15</registrationDate>
<isVerified>true</isVerified>
<balance>150.75</balance>
<website>https://johndoe.com</website>
</user>