In both the commercial and defense sectors a compelling need is emerging for highly dynamic, yet risk optimized, sharing of information across traditional organizational boundaries. Risk optimal decisions to disseminate mission critical tactical intelligence information to the pertinent actors in a timely manner is critical for a mission’s success. In this paper1 , we argue that traditionally decision support mechanisms for information sharing (such as Multi-Level Security (MLS)) besides being rigid and situation agnostic, do not offer explanations and diagnostics for non-shareability. This paper exploits rich security metadata and semantic knowledgebase that captures domain specific concepts and relationships to build a logic for risk optimized information sharing. We show that the proposed approach is: (i) flexible: e.g., sensitivity of tactical information decays with space, time and external events, (ii) situation-aware: e.g., encodes need-to-know based access control policie...