Guys,

It's really good way to mix IDEF0 (or BPMN) and UML. It's difficult to describe BP by using UML but you can (should) use IDEF0 (or BPMN) to do it. Pls keep in mind BP does not have any relationship with SW in general. After that you should drill down and work with SW requirements. At this level you can (should) use UML to model requirements and architecture (use case, activity, class and other diagrams). Many tools support BPMN and UML in one and it's modern trend to mix BPMN and UML in SW development.