1. A system for generating a boosted tag ranking for a media instance, the system comprising: a probabilistic relevance estimator operable to estimate a relevance score for each input tag of the target media instance, wherein each relevance score is associated with a corresponding input tag, wherein the relevance scores are ordered by relevance thus forming a relevance tag ranking; and a tag correlation refiner operable to refine the relevance tag ranking based on tag similarity measurements derived from media instances that share a common tag with the media instance wherein the tag similarity measurements are based on tag exemplar similarity and tag concurrence similarity, wherein the media instances are comprised by at least one media repository.