Information systems for un-regimented domains such as museums, art and book collections, face representational and usability challenges that surpass the demands of traditional information systems for regimented domains. While the former require complex conceptual models supporting a set of dynamic and evolving qualitative properties of a small number of objects, the latter focus on the quantitative aspects of a possibly very large number of objects but with a relatively small and stable set of properties. In this paper we study the use of a non-monotonic knowledge-base system for the development of information systems for un-regimented domains. We discuss the ontological assumptions of the formalism, its structure and its inferential mechanisms through a simple example. Then we present an information system for a highly un-regimented domain in the digital humanities with promising results. The present study shows that the so-called extensible, flexible, dynamic or evolving information systems need the expressive power of non-monotonic knowledge-base systems, and that such phenomena should be addressed explicitly.