In this paper we describe an approach to manage multimedia data in the framework of an advanced information and knowledge management system based on the terminological representation model Back. The guide-lines of the approach are based on using Back to provide conceptual descriptions of multimedia data, and on providing a multimedia object multimedia supporting all functionalities related to the physical organization. The usage of Back as conceptual tool for multimedia data has several advantages, such as adequate expressive power and reasoning capabilities. The multimedia object manager has been designed following an object-oriented approach. The main advantage is to provide extensibility, thus allowing new types of media to dynamically added to the system.