I am not sure if this is already addressed. When I searched I couldn't find this precise problem. Please correct me if I am wrong. A simpletype based on xsd:string will not generate a class and will be of type java.lang.String. If a new simpletype is derived from the first using restriction and enumeration, a new class is generated but is not inherited from java.lang.String as it is not possible to. Using these simpletypes will become impossible in a hierarchy of complextypes. The following schema sample highlights the problem. PartyRole is derived from ObjectRole. Both are simple types, but ObjectRole being just a string does not generated any class. PartyRole being enumeration generates a class. But PartyRole is derived from ObjectRole which is not clearly reflected in the java classes generated. We need simpletypes of this nature to use them in a hierachy of complex types, for e.g. Object, Party. <?xml version="1.0" encoding="UTF-8"?> <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" attributeFormDefault="unqualified"> <xsd:simpleType name="ObjectRole"> <xsd:restriction base="xsd:string"/> </xsd:simpleType> <xsd:simpleType name="PartyRole"> <xsd:restriction base="ObjectRole"> <xsd:enumeration value="Person"/> <xsd:enumeration value="Org"/> </xsd:restriction> </xsd:simpleType> <xsd:complexType name="Object"> <xsd:simpleContent> <xsd:extension base="xsd:string"> <xsd:attribute name="Role" type="ObjectRole"/> </xsd:extension> </xsd:simpleContent> </xsd:complexType> <xsd:complexType name="BaseParty"> <xsd:simpleContent> <xsd:extension base="Object"> <xsd:attribute name="Type" type="xsd:string"/> </xsd:extension> </xsd:simpleContent> </xsd:complexType> <xsd:complexType name="Party"> <xsd:simpleContent> <xsd:restriction base="BaseParty"> <xsd:attribute name="Role" type="PartyRole"/> </xsd:restriction> </xsd:simpleContent> </xsd:complexType> </xsd:schema>