The position value in communication structures

We study cooperation structures with the following property: given any two feasible coalitions with non-empty intersection, its union is a feasible coalition again. TU-games restricted by union stable systems generalize graph-restricted games and games with permission structures. A study about the differences between the position value in union stable systems and hypergraph communication situations is given. Moreover, some computational aspects related to position value in union stable systems are discussed.This research has been partially supported by the Spanish Ministery of Science and Technology, under grant SEC2003-00573.