As social networks, shared editing platforms and other collaborative systems are becoming increasingly popular, the demands for proper protection of the data created and used within these systems grows. Yet, existing access control mechanisms are not suited for the challenges imposed by collaborative systems. Two main challenges should be addressed: collaborative specification of permissions, while ensuring an appropriate levels of control to the different parties involved, and enabling transparency in decision making in cases where the access requirements of these different parties are in conflict. In this paper we propose a data governance model for collaborative systems, which allows the integration of access requirements specified by different users based on their relation with a data object. We also study the practical feasibility of enabling transparency by comparing different deployment options for transparency in XACML.