Hi Eliric,
If you're onPremise (not sure OnD would work the same) you can review chap.6 of asm-channels.pdf about web services integration
The url is defined p94 as
<IncomingHttpServerURL> / <ContextRoot> / soap / <partition> / <topic_name>
an example given is
https://buyer.ariba.com:4443/Buyer/soap/psap/PurchaseOrderExport
Hope that helps
Fred