Context-aware systems aim to deliver a rich user experience by taking into account the current user context (location, time, activity, etc.), possibly captured without his intervention. For example, cell phones are now able to continuously update a user's location while, at the same time, users execute an increasing amount of activities online, where their actions may be easily captured (e.g. login in a web application) without user consent. In the last decade, this topic has seen numerous developments that demonstrate its relevance and usefulness. The trend was accelerated with the...