Advanced XSD: Restrictions, Extensions, and Identity Constraints

Unit 3•CLO02, CLO05

Learning Objectives

Course Learning Outcomes

CLO02

CLO05

Course Outcomes

CO03

ℹ️

Introduction

Advanced schemas capture business rules. XSD can restrict values (ranges, patterns, enumerations), derive new types via extension/restriction, and enforce identity constraints like unique keys.

The Basics

Facets (restrictions)

Common facets:

minInclusive, maxInclusive
pattern
enumeration

Derivation

extension: add new fields
restriction: narrow allowed values

Technical Details

Restriction example

<xs:simpleType name="CgpaType">
  <xs:restriction base="xs:decimal">
    <xs:minInclusive value="0.0"/>
    <xs:maxInclusive value="10.0"/>
  </xs:restriction>
</xs:simpleType>

Enumeration example

<xs:simpleType name="DeptType">
  <xs:restriction base="xs:string">
    <xs:enumeration value="CSE"/>
    <xs:enumeration value="ECE"/>
  </xs:restriction>
</xs:simpleType>

Examples

Pattern example

<xs:simpleType name="PhoneType">
  <xs:restriction base="xs:string">
    <xs:pattern value="[0-9]{10}"/>
  </xs:restriction>
</xs:simpleType>

Real-World Use

Practical

Add restrictions to your schema (enum, range, pattern).
Create one derived type using extension.

📝 For exams

Exam

Explain facets and type derivation.
Discuss identity constraints (key/keyref) conceptually.

✨ Key points

Takeaways

Restrictions encode business rules early.
Type derivation improves reuse.

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XSD Fundamentals: Namespaces, Types, and Structure

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