Our paper deals with the information system design when several responsibilities share a common subset of information. First, we show how to define information overlap situations between these responsibilities. Then we focus on these situations in order to understand how the responsibility areas can avoid information co-ordination misunderstandings.The study of these situations shows how to define the information-sharing protocols between these responsibility areas. From the methodological standpoint, the overlap situation analyses shed a new light on the understanding of co-ordination problems in the distributed IS domain.