On a per-query basis, you can specify a key on which to sort the records and a sort direction.
<Sort Key="keyName" Direction="dirOrder"/>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:ns="http://www.endeca.com/MDEX/conversation/1/0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Header/>
<soapenv:Body>
<ns:Request>
<ns:ContentElementConfig xsi:type="ns:RecordListConfig"
Id="RecordList"
HandlerFunction="RecordListHandler"
HandlerNamespace="http://www.endeca.com/MDEX/conversation/1/0"
MaxPages="2">
<ns:RecordsPerPage>10</ns:RecordsPerPage>
<ns:Page>1</ns:Page>
<ns:Sort Key="ModelName" Direction="Ascending"/>
</ns:ContentElementConfig>
</ns:Request>
</soapenv:Body>
</soapenv:Envelope>