Most queries issued to a search engine are ambiguous at some level. This presents the search engine with a dilemma. On the one hand, if it focuses on the most likely interpretation of the query, it does not provide any utility to users that had a different intent. On the other hand, if it tries to provides at least one relevant results for all query intents, it will not cover any intent particularly well. Dynamic Ranking is a retrieval model that combines these otherwise contradictory goals of result diversification and high coverage. The key idea is to make the result ranking dynamic, allowing limited and well-controllable change based on interactive user feedback. Unlike conventional rankings that remain static after the query was issued, a dynamic ranking allows and anticipates user activity.