Here's what I have so far in schemaeze. Is this enough for now?
<xs:simpleType name="VotingMethodType">
<xs:restriction base="xs:token">
<xs:enumeration value="AMS"/>
<xs:enumeration value="BCM">
<xs:annotation><xs:documentation>Board Count Method</xs:documentation></xs:annotation>
</xs:enumeration>
<xs:enumeration value="CCM">
<xs:annotation><xs:documentation>Condorcet Count Method</xs:documentation></xs:annotation>
</xs:enumeration>
<xs:enumeration value="FPP">
<xs:annotation><xs:documentation>First Past the Post</xs:documentation></xs:annotation>
</xs:enumeration>
<xs:enumeration value="IRV"/>
<xs:enumeration value="NOR"/>
<xs:enumeration value="OPV"/>
<xs:enumeration value="RCV"/>
<xs:enumeration value="SPV"/>
<xs:enumeration value="STV"/>
<xs:enumeration value="cumulative"/>
<xs:enumeration value="approval"/>
<xs:enumeration value="block"/>
<xs:enumeration value="supporterlist"/>
<xs:enumeration value="partisan"/>
<xs:enumeration value="supplementaryvote"/>
<xs:enumeration value="other"/>
</xs:restriction>
</xs:simpleType>