Difference Between xs:include and xs:import in XSD

When modularizing an XML Schema Definition (XSD), xs:include and xs:import are the two primary mechanisms used to combine multiple schema documents. The fundamental difference between them lies in how they handle namespaces: xs:include is used to merge schema documents that share the same target namespace (or adopt the including schema’s namespace), while xs:import is used to bring in schema components from a completely different target namespace.

The Purpose of xs:include

The xs:include element allows you to split a single large schema into smaller, manageable files within the same target namespace.

Key characteristics of xs:include: * Same Namespace: The included schema file must have the identical targetNamespace as the parent schema, or it must not define a targetNamespace at all. * Chameleon Effect: If the included schema has no targetNamespace, it automatically inherits and adopts the targetNamespace of the including schema document. * Attributes: It primarily uses the schemaLocation attribute to specify the URI or file path of the schema to be incorporated.

Example:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           targetNamespace="http://example.com/ns/orders"
           xmlns="http://example.com/ns/orders">
    <xs:include schemaLocation="customer-types.xsd"/>
</xs:schema>

The Purpose of xs:import

The xs:import element allows a schema to reference elements, types, and attributes defined in a different target namespace.

Key characteristics of xs:import: * Different Namespaces: It is strictly used when integrating types across distinct namespaces. * Prefix Binding: To use types from the imported schema, you must declare an xmlns prefix for that namespace at the top of your schema document. * Attributes: It requires a namespace attribute to identify the foreign namespace and typically uses an optional schemaLocation attribute to locate the actual XSD file.

Example:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           targetNamespace="http://example.com/ns/orders"
           xmlns:common="http://example.com/ns/common">
    <xs:import namespace="http://example.com/ns/common" 
               schemaLocation="common-definitions.xsd"/>
    
    <xs:element name="OrderDate" type="common:CustomDateType"/>
</xs:schema>

Summary of Key Differences