XSD - Difference Between ref and type in XSD

Using type (local definition)

Here, we define elements directly with their datatypes.

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           targetNamespace="http://example.com/auth"
           xmlns="http://example.com/auth"
           elementFormDefault="qualified">

  <!-- Local elements -->
  <xs:element name="UserName" type="xs:string"/>
  <xs:element name="Password" type="xs:string"/>

</xs:schema>

✅ XML Output (local namespace elements):

<auth:UserName xmlns:auth="http://example.com/auth">usr</auth:UserName>
<auth:Password xmlns:auth="http://example.com/auth">pwd</auth:Password>

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Using ref (reusing global elements)

First, define global reusable elements in a common schema.

common.xsd

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           targetNamespace="http://example.com/common"
           xmlns="http://example.com/common"
           elementFormDefault="qualified">

  <!-- Global elements -->
  <xs:element name="MessageId" type="xs:string"/>
  <xs:element name="Timestamp" type="xs:string"/>

</xs:schema>

Now, reference those in the service schema.

service.xsd

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           targetNamespace="http://example.com/service"
           xmlns:svc="http://example.com/service"
           xmlns:common="http://example.com/common"
           elementFormDefault="qualified">

  <!-- Import the common schema -->
  <xs:import namespace="http://example.com/common" schemaLocation="common.xsd"/>

  <!-- Reference global elements -->
  <xs:element ref="common:MessageId"/>
  <xs:element ref="common:Timestamp"/>

</xs:schema>

✅ XML Output (reused common namespace elements):

<common:MessageId xmlns:common="http://example.com/common">12345</common:MessageId>
<common:Timestamp xmlns:common="http://example.com/common">2025-09-03T10:00:00</common:Timestamp>

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3. Combined SOAP Example

Both styles used together in a real request:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
                  xmlns:auth="http://example.com/auth"
                  xmlns:common="http://example.com/common">
   <soapenv:Header/>
   <soapenv:Body>
      <auth:LoginRequest>
         <!-- Local elements (defined with type) -->
         <auth:UserName>usr</auth:UserName>
         <auth:Password>pwd</auth:Password>

         <!-- Global reusable elements (referenced with ref) -->
         <common:MessageId>12345</common:MessageId>
         <common:Timestamp>2025-09-03T10:00:00</common:Timestamp>
      </auth:LoginRequest>
   </soapenv:Body>
</soapenv:Envelope>

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✅ Summary

• type → Local definition, used for service-specific fields (UserName, Password).
• ref → Reference to global elements, used for shared fields (MessageId, Timestamp).

This way you can mix both:

• Use type for fields unique to a service.
• Use ref for fields that must come from a common namespace.

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