Effects in OWL-S

Hi all,
I would like to ask a question regarding Effects in OWL-S.  I've tried to
search this archive but didn't manage to find any information regarding such
a construct.  I know that an effect is in essence is something which changes
the state of some object in the world.  However, I didn't come across any
specific implemented construct.  What I would like to know is if there is
any information (papers, links - anything will do) regarding this topic.
 
thanks
James