This paper describes an architecture which supports the user of a CBR system during the modelling and maintaining of the used knowledge. Different maintenance operations are described and characterised along different dimensions. We give an overview of possible operations with their resulting repair strategies. Exemplary, we describe two operations in detail. We examine the impact of maintenance operations to the overall CBR system which leads to the design of an evaluation component. As a result, we describe our architecture for the maintenance of a CBR system. We close with a short discussion.