mapping java type java.util.Map to XML

[santax]

I am devoloping a webservice application using jax-ws2.1

I want write a wsdl and xsd file which applyed the follow function

public void addElement(String id,Map<String,String> repos){
...................
}

relevant chip of wsdl
<message name="addElement">
<part name="parameters" element="tns:addElement"></part>
</message>
<portType name="...">
........
<operation name="addElement">
<input message="tns:addElement"></input>
<output message="tns:addElementResponse"></output>
</operation>

relevant chip of xsd.
<xs:element name="addElement" type="tns:addElement"></
xs:element>
<xs:complexType name="addElement">
<xs:sequence>
<xs:element name="id" type="xs:string" minOccurs="0"></xs:element>
<xs:element name="repos" type="xs:Map???" minOccurs="0"></
xs:element>
------------------------------------------------------------------------------------------------
</xs:sequence>
</xs:complexType>

my question is what type does repos should be?? "xs:Map" is wrong as
i know.

Thanks.