Operations planning is a complex and knowledge intensive process. Products with large numbers of variants, such as products manufactured in a one-of-a-kind production scheme, require that large parts of the operations planning is done automatically or supported by computer-aided systems. Designing such a system for a flexible environment demands certain capabilities as f.e. simple understanding and thus maintaining of the knowledge base or possible user interaction during the planning process for gaining additional knowledge This paper presents an overview over the demands on knowledge-based operations planning systems under special consideration of knowledge management aspects. Within an industry project, this and the results of the study of existing planning systems should lead to a specification and prototype implementation of a new operations planning system for sheet and coil material products.