Help in creating XML Schema

Hi,
Please help me to write a XML Schema reflecting the following java class structure.
Class Response has a collection of Contact objects.
Class Contact has type and group as its attributes.
Class Phone and Class Email are subclasses of Contact.
Following is a sample XML for the same.

I found difficulty in reflecting the inheritance in the above Java structure, in Schema.
Any help would be highly appreciated.
Thanks

<?xml version = "1.0" encoding = "UTF-8"?>
<xsd:schema xmlns:xsd = "http://www.w3.org/2001/XMLSchema" elementFormDefault = "qualified">
<xsd:element name = "Response">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Contact" maxOccurs="unbounded" type="ContactType"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:complexType name="ContactType">
<xsd:sequence>
<xsd:element name = "Phone" maxOccurs = "1">
<xsd:complexType>
<xsd:simpleContent>
<xsd:extension base = "xsd:string">
<xsd:attribute name = "group" use="required" type="xsd:integer"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
</xsd:element>
<xsd:element name = "Email" maxOccurs = "1">
<xsd:complexType>
<xsd:simpleContent>
<xsd:extension base = "xsd:string">
<xsd:attribute name = "group" use="required" type="xsd:integer"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:schema>