This article discusses the implementation of a knowledge base for a library information system. The system was conceived using a typed logic programming language - LOGIN - where type inheritance is built in. The knowledge base is structured in a hierarchical taxonomy of library object classes where each class is represented in a frame style knowledge structure and inherits the properties of its parents, and where infrastructural inference rules have been established through typed Horn clauses. Also in this document, some programming techniques aimed at using the power of inheritance as taxonomic inference are discussed. a Digital Equipment Corporation, Paris Research Lab., 85 avenue Victor Hugo, 92563 Rueil-Malmaison Cedex, France.