I don't believe ORDERED is a valid attribute, I think what we're looking for is "optional".

https://wiki.duraspace.org/display/FCREPO/DSCOMPOSITE-MODEL+and+Schemas

<dsCompositeModel
        xmlns="info:fedora/fedora-system:def/dsCompositeModel#">
    <dsTypeModel ID="DC">
        <form MIME="text/xml"/>
    </dsTypeModel>
    <dsTypeModel ID="ORIGIN" optional="true">
        <form MIME="text/xml"/>
    </dsTypeModel>
</dsCompositeModel>