How to express stateful connections/ Fault handlers in OWL-S ?

Hi, 
 I have been using BPEL4WS for composing web services, and now I've changed
to OWL-S mainly because of semantic features. But how can I use stateful
conversations in OWL-S, how can I garantee that I will receive a result in a
long-running business process.

And even more, I know that in oWL-S we do not have a mechanism of fault
handler, but there is another mechanism to catch the errors? 

Thanks in advance,
DAniela