Hello,
once that you have developed the BPMN model, WebRatio permits you to create, starting from that, a prototying Web Project. From this, you'll be able using WebML to customize this prototype and to improve the features of the Web Application BPM based.
In order to understand better how WebRatio BPM side and WebML side cooperate, I suggest you to take a look to articles on our Wiki in the BPM section
Business Process Model