Why does '/etc/cluster/cluster.conf file' fails to validate with 'xmllint' command ?

Issue

• Why "xmllint" does not validate the below /etc/cluster/cluster.conf file ?

# xmllint -relaxng /usr/share/cluster/cluster.rng /etc/cluster/cluster.conf
<?xml version="1.0"?>
<cluster config_version="21" name="ab_NFS">
    <cman expected_votes="1" transport="udpu" two_node="1"/>
    <clusternodes>
        <clusternode name="node01.yyy.com" nodeid="1" votes="1">
            <fence>
                <method name="1">
                    <device delay="30" name="rhel6_soap" uuid="bcb1-fc3baf3fee76"/>
                </method>
            </fence>
        </clusternode>
        <clusternode name="node02.yyy.com" nodeid="2" votes="1">
            <fence>
                <method name="1">
                    <device name="rhel6_soap" uuid="6133-96123c0a7667"/>
                </method>
            </fence>
        </clusternode>
    </clusternodes>
    <fencedevices>
        <fencedevice agent="fence_vmware_soap" ipaddr="xxxxxx.yyy.com" login="rhelxxxx" name="rhel6_soap" passwd="xxxxxxx" ssl="1"/>
    </fencedevices>
    <rm>
        <failoverdomains/>
        <resources>
            <ip address="x.x.x.x" monitor_link="1"/>
            <clusterfs device="/dev/shared_vg/nfs_lv" force_umount="0" fsid="0" fstype="gfs2" mountpoint="/abshare" name="abcd" options="rw,localflocks,sync,noatime,nodiratime"/>
            <nfsexport name="xxfst"/>
            <nfsclient allow_recover="1" name="xxfst1" options="rw" target="node03.yyy.com"/>
        </resources>
        <service autostart="1" exclusive="0" name="nfss" recovery="relocate">
            <ip ref="x.x.x.x"/>
            <clusterfs ref="abcd">
                <nfsexport ref="xxfst">
                    <nfsclient ref="xxfst1"/>
                </nfsexport>
            </clusterfs>
        </service>
    </rm>
</cluster>
Relax-NG validity error : Extra element rm in interleave
/etc/cluster/cluster.conf:31: element rm: Relax-NG validity error : Element cluster failed to validate content
/etc/cluster/cluster.conf fails to validate