Abstract: An apparatus and system are provided for retrieving electronic records from a database of records, preferably in the form of medical records. The apparatus utilizes a knowledge base in the form of a data structure set forth in a description language. The knowledge base includes representations of a plurality of concepts hierarchically linked with other concepts within a plurality of classes, and non-hierarchically linked with concepts in other classes. A query manager receives a user query and translates the query into the description language. A records analyzer is coupled to the query manager, database and knowledge base. The records analyzer analyzes the records in the database based on the user query and the classes and the hierarchical and non-hierarchical relationships in the knowledge base.