I've been bashing my head about trying to stay scriptless when calling an outbound web service from Siebel 7.8.
I think I've found a neat way which is basically what this link and this link show. What was missing was the ability to set the type to XXXopertation:parameters on the message. Based on what I was just doing, it doesn't look one needs to.
The workflow above shows that we can use the PRM AMI services to get the blank integration object and then directly call the web service. In addition I'm doing some kung fu in order to send an integration object (account interface) to an external web service (hosted in BizTalk) which I have to append to the operation integration object. Fun stuff.