A new generation of information systems that integrates knowledge base technology with database systems is presented for providing cooperative (approximate and conceptual) query answering. Based on the database schema and application characteristics, data are organized into Type Abstraction Hierarchies (TAHs). The higher levels of the hierarchy provide a more abstract data representation than the lower levels. Generalization (moving up in the hierarchy) and specialization (moving down the hierarchy) are the key operations in deriving cooperative query answers for the user. Based on the context, the TAHs can be constructed automatically from databases. A relaxation manager is developed to provide control for query relaxations. A mediator architecture is developed to provide scalability and extensibility. GoBase allows users to specify queries graphicaJly and incrementally on the map, greatly improving querying capabilities. CoBase has been demonstrated to answer imprecise queries for ARPI transportation planning.