You need to load data into the interface tables, following which you can call the API. I dont have exact details of API. But I do remember seeing this methodology work whereby Requisitions from iProcurment get converted into Purchase Orders. Even standard functionality dumps data into po_header_interface when converting Requisitions into PO's
Actually my main requirement is to get the PO detail message from MQ series (another appliaction) to SOA and then create PO in oracle appliaction.
So what I am planning is to get the details and insert it into PO interface table and then call the standard program. I am also trying to use SOA apps adaptor if it can help me to import the data to interface table and call the conc program (if it is available as service), till now nothing got from soa apps adaptor.
Once you read the payload from MQ, you can then have transform activity to convert that payload into a structure that matches PO Interface tables. Next, use Database adapter to push that message to Oracle Apps via a stored procedure
Simply login via http://irep.oracle.com/ And then expand the procurement section, you will see that Standard Purchase Order is exposed in iRep as Web service. You should be able to create Partner link using apps adapter for this. Hence this will give you the schema that Oracle expects for Standard PO.