XML Tutorial/XML Schema/Annotation

Annotating Schemas: add information about your schema or its elements.

You can create annotations right after the xsd:schema element to document the entire schema.
<annotation id="ID"
            {any attributes with non-schema namespace}>
  Content: (appInfo | documentation)*
</annotation>

File: Schema.xsd
<xsd:schema xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">
  <xsd:annotation>
    <xsd:documentation>
      test
    </xsd:documentation>
  </xsd:annotation>
</xsd:schema>

Annotations for element tags

<?xml version = "1.0" ?>
<xs:schema xmlns:xs = "http://www.w3.org/2001/XMLSchema">
   <xs:annotation>
      <xs:documentation>
         Schema for customer name information.
      </xs:documentation>
   </xs:annotation>
   <xs:element name = "Customer">
       <xs:annotation>
          <xs:documentation>
             MiddleInitial is optional 
          </xs:documentation>
       </xs:annotation>
      <xs:complexType>
         <xs:group ref = "NameGroup" />
      </xs:complexType>
   </xs:element>
   <xs:group name = "NameGroup">
      <xs:sequence>
         <xs:element name = "FirstName" type = "xs:string" />
         <xs:element name = "MiddleInitial" type = "xs:string" />
         <xs:element name = "LastName" type = "xs:string" />
      </xs:sequence>
   </xs:group>
</xs:schema>

Annotations provides documentation information, as well as additional application information

<annotation id="unique identifier"> 
The <annotation> declaration can appear as a child of most XML Schema declarations. 
The <annotation> declaration adds two forms of information to your declarations:
Application information 
Documentation information 
Each <annotation> declaration may contain the elements <appinfo> and <documentation>. 
These elements may contain any XML content from any namespace. 
Each of these elements may also contain a source attribute. 
The source attribute is used to refer to an external file that may be used for application information or documentation information. 
Annotations usually include <documentation> declarations to describe the features, or uses, of a particular declaration within the XML Schema.