As libraries and information services address the needs of users in an increasingly networked environment, there is a need for theoretical models to underpin research, development and practice. The characteristics and roles of traditional libraries and information services are described, and a variety of predictions about their future are examined. A number of recent models of the ‘electronic’ or ‘digital’ library are analysed, and the concept of the ‘hybrid’ library is described. On this basis a generic model of the library, using that term in its broadest sense, is developed. A number of application areas are identified