The Grid is a major step towards achieving coordinated resource sharing and problem solving within and among virtual organizations. Grid’s decentralized nature along with the complexity posed by distributed computation set new challenges for security administrators. In this paper we argue that in order to enhance security management in the Grid, and thus provide answers to the aforementioned challenges, we need to look security policy negotiation from a generic perspective. To do so, we delve deeper into the security policy notion and discover the importance of taming security policy semantics and using uniform policy representations. We present the Security Policy Ontology (SPO) notion along with basic SPO design criteria. Finally, we use the SPO notion to construct a generic framework that enhances security policy negotiation in the Grid; we exemplify using two simple security policies.