"simpleType" Components with "union" Child Components

XSD Tutorials - Herong's Tutorial Examples - Version 5.10, by Dr. Herong Yang

XSD Tutorials - Herong's Tutorial Examples

∟"simpleType" - Defining Your Own Simple Datatypes

∟"simpleType" Components with "union" Child Components

This section describes the 'union' child component in 'simpleType' component. 'union' child components are used to create a union of value spaces from multiple member datatypes.

"union" child component in a "simpleType" component offers a different way of defining a new simple datatype by combining value spaces from multiple other simple datatypes.

Here is an XSD template showing you how to use the "union" as a child component in a "simpleType" component:

Format 1:
<simpleType ...>
  <union memberTypes="member_type_list">
</simpleType>

Format 2:
<simpleType ...>
  <union>
    <simpleType ...>
      definition of member datatype 1
    </simpleType>
    <simpleType ...>
      definition of member datatype 2
    </simpleType>
    ...
  </union>
</simpleType>

Some notes on using the "union" component:

memberTypes="member_type_list" - Optional attribute to specify multiple datatypes to be used as members of the union. If not provided, member datatypes must be defined with child "simpleType" components.
Child "simpleType" components are always allowed to add more member datatypes, even memberTypes="member_type_list" is provided.

For example, the following XSD document uses "union" components to define 2 new simple datatypes:

<?xml version="1.1"?>
<!-- union_simpleType_test.xsd
 - Copyright (c) 2013, HerongYang.com, All Rights Reserved.
-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="Union_SimpleType_Test">
  <xs:complexType>
    <xs:sequence>

    <xs:element name="MixedData" maxOccurs="unbounded">
        <!-- "union" with "memberTypes" attribute -->
        <xs:simpleType>
          <xs:union memberTypes="xs:integer xs:NCName"/>
        </xs:simpleType>
      </xs:element>
    
    <xs:element name="Month" maxOccurs="unbounded">
        <!-- "union" with no "memberTypes" attribute -->
        <xs:simpleType>
          <xs:union>
            <xs:simpleType>
              <xs:restriction base="xs:unsignedByte">
                <xs:minInclusive value="1"/>
                <xs:maxInclusive value="12"/>
              </xs:restriction>
            </xs:simpleType>            
            <xs:simpleType>
              <xs:restriction base="xs:NCName">
<xs:pattern value="Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec"/>
              </xs:restriction>
            </xs:simpleType>
          </xs:union>
        </xs:simpleType>
      </xs:element>

    </xs:sequence>
  </xs:complexType>
</xs:element>
</xs:schema>

Here is a sample XML document to test the above XSD document:

<?xml version="1.1"?>
<!-- union_simpleType_test.xml
 - Copyright (c) 2013, HerongYang.com, All Rights Reserved.
-->
<Union_SimpleType_Test>

   <!-- Valid "MixedData" values -->
   <MixedData>  100000  </MixedData>
   <MixedData>  Million  </MixedData>

   <!-- Invalid "MixedData" values -->
   <MixedData>  Unit:Million  </MixedData>
   
   <!-- Valid "Month" values -->
   <Month>  5  </Month>
   <Month>  May  </Month>

   <!-- Invalid "Month" values -->
   <Month>  13  </Month>
   <Month>  may  </Month>
</Union_SimpleType_Test>

When validating this XML document with my XsdSchemaValidator.java program presented earlier in the book, I get these errors:

c:\Progra~1\Java\jdk1.7.0_07\bin\java XsdSchemaValidator 
   union_simpleType_test.xsd union_simpleType_test.xml
   
Error:
   Line number: 12
   Column number: 43
   Message: cvc-datatype-valid.1.2.3: '  Unit:Million  ' is not a 
   valid value of union type 
   '#AnonType_MixedDataUnion_SimpleType_Test'.

Error:
   Line number: 12
   Column number: 43
   Message: cvc-type.3.1.3: The value '  Unit:Million  ' of element 
   'MixedData' is not valid.

Error:
   Line number: 19
   Column number: 25
   Message: cvc-datatype-valid.1.2.3: '  13  ' is not a valid value of
   union type '#AnonType_MonthUnion_SimpleType_Test'.

Error:
   Line number: 19
   Column number: 25
   Message: cvc-type.3.1.3: The value '  13  ' of element 'Month' is 
   not valid.

Error:
   Line number: 20
   Column number: 26
   Message: cvc-datatype-valid.1.2.3: '  may  ' is not a valid value 
   of union type '#AnonType_MonthUnion_SimpleType_Test'.

Error:
   Line number: 20
   Column number: 26
   Message: cvc-type.3.1.3: The value '  may  ' of element 'Month' is 
   not valid.

Failed with errors: 6

Last update: 2013.

Table of Contents

About This Book

Introduction to XML Schema

XML Editor and Schema Processor - XMLPad

Java API for XML Processing - JAXP

JAXP - XML Schema (XSD) Validation

Xerces2 Java Parser - Java API of XML Parsers

Using Xerces2 Java API

XML Schema Language - Basics

Introduction of XSD Built-in Datatypes

"string" and Its Derived Datatypes