These are the papers, discussion notes and workshop reports of ISCO4, the fourth international conference in a series instigated by the former IFIP Working Group 8.1 Task Group FRISCO (FRamework of Information System COncepts). The FRISCO Report - published in 1998 - forms a contribution to the quest towards developing a scientific outlook in the field of information systems. ISCO4 provided a forum for debate on that report and on a range of related issues, including: reflections on and criticism of conceptual frameworks (such as FRISCO); fundamental and generic information system concepts; novel information system design approaches; approaches to integrate and synthesize information system design methods. The three workshops addressed the following themes: the conceptual foundations of information systems; innovation and standardization in the information system field; how do our concepts shape our practice, and vice versa? ISCO4 was held in the Lorentz Center of Leiden University, The Netherlands, in September 1999, and was sponsored by the International Federation for Information Processing (IFIP).