The more you want, the more you have to pay for it. In the context of Computer Science this often means, the more control the user wants to keep on her system, the more effort is required on her side to let it tailor her personal needs. This applies to security-related issues as well: on the one hand, available out-of-the-box solutions provide the user with predefined security profiles, thereby not allowing for fine-grained control they may desire in many real-world scenarios. On the other hand, existing solutions supporting personalization to a greater extent can be hardly exploited without an unaffordably long learning period. This book describes Protune, a special-purpose programming language enabling the definition of formal policies to protect sensitive resources, and especially focuses on its interface to ease the policy definition process. The feasibility of the approach is demonstrated by applying it to meaningful real-world problems. This book should be especially useful to security experts and in general to Semantic Web researchers since it provides a broad overview of current policy languages and reports about one of the most complete policy languages available to date.