Define an xsd enumeration once to be used in multiple places?

I want to use the following enumaration in multiple plac开发者_StackOverflow社区es, but as you can see now, it is tied to one complex type, how do I extract it out so I can define it once and use it in multiple places.

<xs:complexType name="MessageType">
    <xs:sequence>
        <xs:element name="Control" type="ControlType" minOccurs="1" maxOccurs="1" />
        <xs:element name="LOS" type="LOSTYPE" minOccurs="0" maxOccurs="1" />
        <xs:element name="UID" type="UIDTYPE" minOccurs="1" maxOccurs="1"  />
        <xs:element name="RS" type="RSTYPE" minOccurs="0" maxOccurs="1" />
    </xs:sequence>
    <xs:attribute name="BL" type="xs:string" use="optional"></xs:attribute>
    <xs:attribute name="BLM" use="optional">
        <xs:simpleType>
            <xs:restriction base="xs:string">
                <xs:enumeration value="One" />
                <xs:enumeration value="Two"/>
                <xs:enumeration value="Three"/>
            </xs:restriction>
        </xs:simpleType>
    </xs:attribute>         
</xs:complexType>

Basically, I want to extract the BLM enumeration attribute out so I can define it once and use it multiple places if need so I don't have to repeat it. DRY in a nutshell :)

You can create a named xs:simpleType out of it.

<xs:simpleType name="myEnum">
    <xs:restriction base="xs:string">
        <xs:enumeration value="One" />
        <xs:enumeration value="Two"/>
        <xs:enumeration value="Three"/>
    </xs:restriction>
</xs:simpleType>

And then use it with

<xs:attribute name="BLM" use="optional" type="myEnum"/>