how to define SSN format in WSDL

[grace smith]

Hello,

I am using Websphere java to wsdl tool generate the wsdl for a webservice.
I am wondering where and how should I define the element part constraits - say the SSN should be in format of 9 digit number without any '-'.

Should the WSDL schema define this or should WSDL define some fault part if client passed in wrong format SSN?

here is my part of my WSDL, how should I define the constraints for SSN?

<element name="findBySSN">
<complexType>
<sequence>
<element name="SSN" nillable="true" type="xsd:string"/>
</sequence>
</complexType>
</element>