When developing, implementing, and maintaining large-scale information systems, many facets of knowledge become relevant. Based on experiences in ESPRIT project DAIDA, we analyze these facets and sketch a comprehensive formal model of knowledge relevant to IS development and maintenance. Such a model can be used to structure development environments, to discuss and control software projects, and
... [Show full abstract] to support design decisions and their tool-assisted execution in CASE environments. Based on this model, we have implemented a knowledge-based and decision-oriented software information system called which provides efficient management of large bases of conceptual models and tools for exploratory analysis and (group) decision-making in IS engineering.