Advanced Policy Explanations on the Web

The frameworks for protecting security and privacy can be effective only if common users-with no training in computer science or logic-increase their awareness and control over the policy applied by the systems they interact with. Towards this end, we introduce a mechanism for answering why, Why-not, how-to, and what-if queries on rule-based policies for trust negotiation. Our framework is lightweight and scalable but it fulfills the main goals of modern explanation facilities. We adopt a novel tabled explanation structure, that simultaneously shows local and global (intra-proof and inter-proof) information, thereby facilitating navigation. Answers are focussed by removing irrelevant parts with suitable heuristics.