The emergence of grid and cloud computing systems has introduced new security concepts, so it requires new access control approaches. Traditional systems engineering processes can be enriched with helper approaches that can facilitate the definition of access control requirements in such complex environments. Looking towards a holistic approach on the definition of access control requirements, we propose a four-layer conceptual categorization. In addition, an example is given so that to demonstrate the utilization of the proposed categorization in a grid scenario for defining access control requirements, and evaluate their fulfilment vis-à-vis contemporary employed access control approaches.