webservice to webservice scenario

Dear Experts,

Could you please help me in solving the below queries

In SOAP TO SOAP Scenario Sender is one WSDL and Receiver is another WSDL,after completing Scenario we can generate a WSDL from XI Configuration->Define Webservices, if we test the WSDL then only the Data is getting transferred from Sender to Reciever.

Queries

My question is Without using XI System generated WSDL is there any way to trigger the Sender to send the data to Reciever

Another query is if it is Possible only with XI WSDL then how to trigger the Sender (SAP and NON-SAP)