XML Schema Google Web Service

[johnsocs]

All I'm trying to write an xml schema for the following xml from the
google web service api. In the schema I'm not sure how to describe the
soapenv:encodingStyle attribute.

Thanks.

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>

<ns1:doSpellingSuggestion
soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:ns1="urn:GoogleSearch">
<key xsi:type="xsd:string">XXXXXXXXXXXXXXXXXXXXX</key>
<phrase xsi:type="xsd:string">rabbbit</phrase>
</ns1:doSpellingSuggestion>

</soapenv:Body>
</soapenv:Envelope>

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="urn:GoogleSearch"
xmlns:ns1="urn:GoogleSearch"
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
version="1.0">

<xsd:element name="doSpellingSuggestion"
type="ns1:doSpellingSuggestion"/>

<xsd:complexType name="doSpellingSuggestion">
<xsd:sequence>
<xsd:element name="key" type="xsd:string"/>
<xsd:element name="phrase" type="xsd:string"/>
</xsd:sequence>
<xsd:attribute name="encodingStyle" type="soapenv:encodingStyle" />
</xsd:complexType>

</xsd:schema>
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema
xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified"
targetNamespace="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:ns1="urn:GoogleSearch"
version="1.0">

<xs:import namespace="urn:GoogleSearch"
schemaLocation="GoogledoSpellingSuggestion.xsd" />

<xs:element name="Envelope">
<xs:complexType>
<xs:sequence>
<xs:element name="Body">
<xs:complexType>
<xs:sequence>
<xs:element ref="ns1:doSpellingSuggestion" />
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>

</xs:schema>