NOTATIONs

Hi,
According to datatypes: "It is an error for NOTATION to be used directly
in a schema. Only datatypes that are derived from NOTATION by specifying
a value for enumeration can be used in a schema. Furthermore, the value
of all enumeration facets must match the name of a notation declared in
the current schema."

However, in structures I can find example:
<xs:notation name="jpeg"
             public="image/jpeg" system="viewer.exe" />
<xs:element name="picture">
 <xs:complexType>
  <xs:complexContent>
   <xs:extension base="xs:binary">
    <xs:attribute name="pictype" type="xs:NOTATION"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>
</xs:element>

Is " <xs:attribute name="pictype" type="xs:NOTATION"/>" allowed? 
And if yes, what do you mean by "It is an error for NOTATION to be used
directly in a schema."? [datatypes].

Thank you,
Elena