# Behind the scenes: Transforming XSD to Ecore

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