This paper deals with special problems of knowledge base maintenance which have to be solved within the knowledge acquisition process. We illustrate that aspects of maintenance must be taken into account by the design model construction because dependencies between pieces of knowledge can result in inconsistent states of a knowledge base. We describe a Knowledge Dependency Network which extends ideas from truth maintenance systems to detect and manage these inconsistencies. The network allows formal definitions of inconsistency conditions and checks them automatically preserving the integrity of the knowledge base. As a fundamental part of the acquisition and maintenance environment the knowledge dependency network supports the conventional development and editing of a knowledge base.