use of derivedBy

In the September 22, 2000 working draft of "XML Schema Part 1: Structures",
there is the following example:

<xs:element name="picture">
  <xs:complexType base="xs:binary" derivedBy="extension">
    <xs:attribute name="pictype" type="xs:NOTATION"/>
  </xs:complexType>
</xs:element>

I cannot find "derivedBy" in any other locations in the documents; has
derivedBy been replaced by the <extension> tag?

Garret Wilson
GlobalMentor, Inc.
garret@globalmentor.com