[oXygen-user] XML Schema question

[Timothy Reaves]

     I have an XML Schema I'm trying to lock down (to do more validation
for me).  I have an element with a required attribute that I restrict
as shown below.

<xsd:element name="MyElement1">
  <xsd:complexType>
    <xsd:sequence>
      <xsd:element name="Description" minOccurs="0" type="xsd:string"/>
      <xsd:element maxOccurs="unbounded" ref="MyElement2"/>
      <xsd:element maxOccurs="unbounded" ref="MyElement3"/>
      <xsd:element maxOccurs="unbounded" ref="MyElement4"/>
    </xsd:sequence>
    <xsd:attribute name="scope" use="required">
      <xsd:simpleType>
        <xsd:restriction base="xsd:string">
          <xsd:enumeration value="scope1"/>
          <xsd:enumeration value="scope2"/>
          <xsd:enumeration value="scope3"/>
          <xsd:enumeration value="scope4"/>
        </xsd:restriction>
      </xsd:simpleType>
    </xsd:attribute>
  </xsd:complexType>
</xsd:element>


What I want to do is have MyElement3 only allowable in a MyElement1 where
scope == scope2 (for example).  So have a rule on an element that
restricts what element can contain it based on the attribute value.

     Is this possible?  Any pointer to documentation doing something like
this?  Thanks!