<sdc4:Cluster xmlns:sdc4="https://semanticdatacharter.com/ns/sdc4/">
  <label>{0,1}</label>
  <sdc4:Items>{0,unbounded}</sdc4:Items>
</sdc4:Cluster>

<xs:element name="Cluster" substitutionGroup="sdc4:Item" type="sdc4:ClusterType">
  <xs:annotation>
    <xs:appinfo>
      <rdf:Description rdf:about="https://semanticdatacharter.com/ns/sdc4/sdc4.xsd#Cluster">
        <rdfs:subClassOf rdf:resource="https://semanticdatacharter.com/ns/sdc4/sdc4/CMS"/>
        <sdc4:isCMSOf rdf:resource="https://semanticdatacharter.com/ns/sdc4/sdc4.xsd#ClusterType"/>
        <rdf:type rdf:resource="https://semanticdatacharter.com/ns/sdc4/sdc4/CMS"/>
      </rdf:Description>
    </xs:appinfo>
  </xs:annotation>
</xs:element>