Restrict use of an attribute in an XSD assertion
问题 Given XSD: <xs:element name="color"> <xs:complexType> <xs:attribute name="type"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="white"/> <xs:enumeration value="black"/> <xs:enumeration value="red"/> <xs:enumeration value="green"/> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:attribute name="number" use="optional/> </xs:complexType> </xs:element> How would I write an assertion so that if <color> has @type white or black, it cannot also have the @number