The include element is used to add multiple schemas with the same target namespace to a document.
(The ? sign declares that the element can occur zero or one time inside the include element)
|id||Optional. Specifies a unique ID for the element|
|schemaLocation||Required. Specifies the URI to the schema to include in the target namespace of the containing schema|
|any attributes||Optional. Specifies any other attributes with non-schema namespace|
With included schemas, the included files must all reference the same target namespace. If the schema target namespace don't match, the include won't work: