caps.xsd

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='http://jabber.org/protocol/caps'
    xmlns='http://jabber.org/protocol/caps'
    elementFormDefault='qualified'>

  <xs:annotation>
    <xs:documentation>
      The protocol documented by this schema is defined in
      XEP-0115: https://xmpp.org/extensions/xep-0115.html
    </xs:documentation>
  </xs:annotation>

  <xs:element name='c'>
    <xs:complexType>
      <xs:simpleContent>
        <xs:extension base='empty'>
          <xs:attribute name='ext' type='xs:NMTOKENS' use='optional'/>
          <xs:attribute name='hash' type='xs:NMTOKEN' use='required'/>
          <xs:attribute name='node' type='xs:string' use='required'/>
          <xs:attribute name='ver' type='xs:string' use='required'/>
        </xs:extension>
      </xs:simpleContent>
    </xs:complexType>
  </xs:element>

  <xs:simpleType name='empty'>
    <xs:restriction base='xs:string'>
      <xs:enumeration value=''/>
    </xs:restriction>
  </xs:simpleType>

</xs:schema>