So the element:
<foo bar="bar" baz="baz"/>
is described using:
<xs:complexType name="foo">
<xs:simpleContent>
<xs:extension base="xs:string">
<xs:attribute name="bar" type="xs:string"/>
<xs:attribute name="baz" type="xs:string"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
nice!