The 'include' element occurs at the top level.

Example:

<xs:include schemaLocation="some-module.xsd"/>
<xs:include schemaLocation="http://cde.berkeley.edu/schemas/chunk-of-something.xsd"/>

The target namespace of the included schema must:

• match the current target namespace (i.e. the targetNamespace attributes have the same value).

• have no value (e.g. no targetNamespace attribute).

All top-level elements become part of the current target namespace.