The first child of 'element' can be an 'annotation' element.

Example:

<xs:element name="person-name">
<xs:annotation>
<xs:documentation xmlns="http://www.w3.org/1999/xhtml">
<p>This element represents a person's name.  The middle name is optional.</p>
</xs:documentation>
</xs:annotation>
...
</xs:element>