15.2.10. XSD empty element

Compound empty elements: ¶

An empty XML element:

<product prodid="1345" />

The “product” element above has no content at all. In order to define a type without content, we must declare a type that contains only elements in its content, but we do not actually declare any elements, such as this:

<xs:element name="product">
  <xs:complexType>
    <xs:complexContent>
      <xs:restriction base="xs:integer">
        <xs:attribute name="prodid" type="xs:positiveInteger"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
</xs:element>

In the above example, we define a composite type with composite content. The complexContent element signals that we intend to define or extend the content model of a composite type, while the integer qualification declares an attribute but does not introduce any element content.

However, you can also declare this “product” element more compactly:

<xs:element name="product">
  <xs:complexType>
    <xs:attribute name="prodid" type="xs:positiveInteger"/>
  </xs:complexType>
</xs:element>

Or you can give a name to a complexType element, then set a type attribute for the “product” element and reference the complexType name (by using this method, several elements can refer to the same compound type):

<xs:element name="product" type="prodtype"/>
<xs:complexType name="prodtype">
  <xs:attribute name="prodid" type="xs:positiveInteger"/>
</xs:complexType>