we take the complete header from the cXMl -
<Header>
<From>
<Credential domain="DUNS">
<Identity>cXML-t</Identity>
</Credential>
</From>
<To>
<Credential domain="DUNS">
<Identity>cXML-t</Identity>
</Credential>
</To>
<Sender>
<Credential domain="DUNS">
<Identity>cXML-t</Identity>
<SharedSecret>test</SharedSecret>
</Credential>
<UserAgent>Coupa Procurement 1.0</UserAgent>
</Sender>
1) FROM and To : you can take domain as , NetworkId, DUNS, SAP, whatever your/supplier system allow
Identity => for ariba, they were provides the Ariba Network Id (ANID) for both buyer and suppliers, other wise put anything , e.g. your name/ company namve also
2) Sender , Credentials domain can be NetworkId, DUNS, SAP, whatever your/supplier system allow
Identity : email id or user name (which provided by buyer system login)
SharedSecret : passord.
Here, if you are working with Ariba system and the buyer and supplier having the ANID, then they allowed/want to validate and login to the catalog with those other wise using sender credentials as cXML user guide explain.