How to start a process out of Web Dynpro?
Once a process is deployed it exposes itself as a web service (so called 'web service provisioning'). Thus you could import this web service model into the Web Dynpro project and execute it like any other web service. As a result a new process instance will be started off with each successful web service request.
Starting with 7.30 one has also the possibility to make use of the BPM Public API.