XML Schema Complete Reference, The

6.14. Imports and Includes

An XML schema document may reference components outside the document by importing or including these components from another XML schema document. The include element adds components to the current schema. In particular, the include element provides a mechanism to assemble an XML schema from a set of XML schema documents. An import element, on the other hand, permits a schema to include components in a different namespace.

Sections 7.8 and 7.9 provide details and examples of how to use include and import, respectively.