[ajuc]

I use state machine of sort (jbpm) in the backed to drive business processes. We have thin client connecting to database, nodes in state machine are actions on databes, or screens we show to user (with inputs possibly). Edges are transitions between screens. Edges can have conditions on them. It's all saved in database between requests, and request/response moves state throught transitions to the next interaction node (possible going throught a few action nodes doing sth on the databsae).

Any exception on the way rollbacks the whole state, and we commit only when we reach next interaction node.

It works great.