What is the right way to get XML commands to JobScheduler (presumably the JobScheduler web service)?
One method for forwarding XML commands to JobScheduler is using our Java class library.
This is described in: How can I generate new jobs and orders automatically?
A possible alternative is the creation of XML files and putting them in the live-folder. Which method you choose depends on how persistent the JobScheduler objects have to be. All objects in the live folder are persistent, objects created by the external API (XML commands) are not.
All changes made to objects created by the external API are lost after JobScheduler is restarted.
Regarding the JobScheduler "WebService": you are able to use the service to send some commands - but not all - as SOAP requests to JobScheduler but note that there will be no WSDL and JobScheduler itself will not be aware of the webservice. There will be a conversion based on XSLT for incoming and outgoing SOAP messages. These XSLTs have to be adjusted to your requirements. If you do not really need to use SOAP messages, it will be more efficient to use TCP/IP or HTTP instead.
You can read more about how to create a web service and the XSLT transformations required in the JobScheduler Web Service documentation.