The Uncertainty of the Truth

How to trust without knowing the truth? This is probably the key question that arises while designing applications using virtual tags. A virtual tag is a geo-referenced note that is visible for all the people that are in a specific place. But what if you see a tag about an event or an object that is not here? How to know if you are facing a spam attack, or if the tag is simply outdated? And, how to update the trust values of the author and the other people that confirmed the tag, since you do not know if they are honest? To answer these questions, we designed and implemented FoxyTag, a free and collaborative system which consist in posting virtual tags over speed cameras in order to warn the other drivers. We used it to test our new generic trust engine and got very promising results.