Attribute and Sequence

Can an "attribute" be part of a sequence. Also, does this have to change to complex type from simple?

开发者_开发问答<xs:simpleType name="t_name">
  <xs:attribute name="a_name" >
     <xs:simpleType>
        <xs:restriction base="xs:hexBinary" >
           <xs:length value="4”/>
       </xs:restriction>
     </xs:simpleType>
   </xs:attribute>
</xs:simpleType>

Thanks, Mohmd.

Only elements are applicable for sequencing. Attributes can not have predefined or mandated order.