XSD Empty Elements
An empty complex element cannot have contents, only attributes.
Complex Empty Elements
An empty XML element:
<product prodid="1345" />
The "product" element above has no content at all. To define a type with no content, we must define a type that allows elements in its content, but we do not actually declare any elements, like 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 example above, we define a complex type with a complex content. The complexContent element signals that we intend to restrict or extend the content model of a complex type, and the restriction of integer declares one attribute but does not introduce any element content.
However, it is possible to declare the "product" element more compactly, like this:
<xs:element name="product">
<xs:complexType>
<xs:attribute name="prodid" type="xs:positiveInteger"/>
</xs:complexType>
</xs:element>
Or you can give the complexType element a name, and let the "product" element have a type attribute that refers to the name of the complexType (if you use this method, several elements can refer to the same complex type):
<xs:element name="product" type="prodtype"/>
<xs:complexType name="prodtype">
<xs:attribute name="prodid" type="xs:positiveInteger"/>
</xs:complexType>
