XML schema with attributes

<xs:complexType name="MessageAbstractType" abstract="true">
  <xs:sequence>
    <xs:element name="AP_Info">
      <xs:complexType>
        <xs:attribute name="AP_ID" type="xs:anyURI" use="required" />
        <xs:attribute name="AP_TransID" type="xs:NCName" use="required" />
        <xs:attribute name="AP_PWD" type="xs:string" use="required" />
        <xs:attribute name="Instant" type="xs:dateTime" use="required" />
        <xs:attribute name="AP_URL" type="xs:anyURI" use="optional" />
      </xs:complexType>
    </xs:element>
    <xs:element name="MSSP_Info">
      <xs:complexType>
        <xs:sequence>
          <xs:element name="MSSP_ID" type="mss:MeshMemberType" />
        </xs:sequence>
        <xs:attribute name="Instant" type="xs:dateTime" use="optional" />
      </xs:complexType>
    </xs:element>
  </xs:sequence>
  <xs:attribute name="MajorVersion" type="xs:integer" use="required" />
  <xs:attribute name="MinorVersion" type="xs:integer" use="required" />
</xs:complexType>