In the code generation process an XML Schema is transformed to an
EMF Ecore model, which is then used as a meta model by EMF. XSD complex
data types are mapped to EClasses, XSD simple data types are mapped to EMF
data types defined in
org.eclipse.emf.ecore.xml.type.XMLTypePackage
and
org.eclipse.xtend.typesystem.xsd.XSDMetaModel
maps them to Xpand
data types. The document
XML
Schema to Ecore Mapping
explains the mapping's details.
http://www.eclipse.org/modeling/emf/docs/overviews/XMLSchemaToEcoreMapping.pdf