In this paper we present an approach to derive User Interface (UI) from ontologies. It automatically generates UI according to declarative model specifications, and the UI helps a novice user to construct valid queries against a Knowledge Base (KB). The UI represents queries by OWL, and then transfers them to concrete applications for matchmaking. A novel aspect of our approach is that the ontological KB used by UI generator is exactly the one used by applications; hence the refining of ontologies needs not refining UI. Further, during a user-machine interaction session, the system eliminates every illegal option that engenders a clash in the KB, so the consistent checking of user inputs is accomplished as a side effect. It boosts the development of a knowledge dense system, as the building of a KB in progress, the UI is generated simultaneous.