Traditional security policies are often based on the concept of "need to know" and are typified by predefined and often rigid specifications of which principals and roles are pre-authorized to access what information. A recommendations of the 9/11 commission was to find ways to move from this traditional perspective toward one that emphasizes the "need to share". Ravi Sandhu and his colleagues have developed the Group centric secure information sharing model (gSIS) as a new model that is more adaptible to highly dynamic situations requiring information sharing. We present an implementation of gSIS and demonstrate its usefulness to usecases in information sharing in social media. Our contributions include the prototype implementation, extension to the model such as hierarchical groups and necessary and sufficient conditions, and the use of the semantic Web language OWL for representing the central gSIS concepts and associated data. Our framework uses a pragmatic approach of using semantic web technology to represent and reason about the hierarchy and procedural method to compute access decisions relying on the gSIS semantics.

• Dr. Tim Finin (chair)
• Dr. Anupam Joshi
• Dr. Yelena Yesha
• Dr. Laura Zavala