dx:composition 

to express the fact that the element is in fact a group of elements linked with the composition expressed in the is

Element Information

Model

Attributes

QName Type Fixed Default Use Inheritable Annotation
dx:is restriction of xs:token optional
dx:name xs:string optional

Source 

<xs:element name="composition" minOccurs="0">
  <xs:annotation>
    <xs:documentation>to express the fact that the element is in fact a group of elements linked with the composition expressed in the is</xs:documentation>
  </xs:annotation>
  <xs:complexType>
    <xs:attribute name="is">
      <xs:simpleType>
        <xs:restriction base="xs:token">
          <xs:enumeration value="all"/>
          <xs:enumeration value="choice"/>
          <xs:enumeration value="interleave"/>
          <xs:enumeration value="sequence"/>
        </xs:restriction>
      </xs:simpleType>
    </xs:attribute>
    <xs:attribute name="name" type="xs:string"/>
  </xs:complexType>
</xs:element>

Sample