XML Tutorial/XML Schema/include

<include> Declarations

<include schemaLocation=""> 

The <include> declaration combines XML Schemas that are designed for the same targetNamespace(or no targetNamespace). 
Within the <include> declaration there is no namespace attribute. 
The <include> declaration can be used only on documents with the same targetNamespace, or no targetNamespace.
When a schema validator encounters an <include> declaration, it treats the global declarations from the included XML Schema as 
  if they had been declared in the XML Schema that contains the <include> declaration.