xsd polymorphism

i am kinda repeating doubt bit 1st asked incorrectly.

i have this:

<xsd:complextype name="a">
        <xsd:sequence>
            <xsd:element name="options" type="options"/>
        </xsd:sequence>
</xsd:complextype>

<xsd:complextype name="b">  
    <xsd:complexcontent>
            <xsd:element name="options" type="ex_options"/>
    </xsd:complexcontent>
</xsd:complextype>

<xsd:complextype name="options">
    <xsd:sequence>
        ...some options
    </xsd:sequence>
</xsd:element>

<xsd:complextype name="ex_options">
    <xsd:complexcontent>
         <xsd:extension base="options">
             <xsd:sequence>
              ...some some-more options
              </xsd:sequence>
          </xsd:extension>
     </xsd:complexcontent>
 </xsd:element>

so fundamentally i have category an middle category options
class b inherits category i wish b.options get a.options webservices wholly need pass getoptions relapse right vigilant b.options. now proceed xsd stands i an blunder observant churned elements name options opposite forms seem denote group. errors b type.