The data model is the heart of interface design

For the past six years, we have been developing a commercial hypermedia system (KMS) based on our previous research with the ZOG system at Carnegie Mellon University. Our experience with ZOG and KMS has convinced us that the data model underlying an interactive system is more important than the user interface in shaping the overall system. In this paper, we show how the KMS data model has influenced important aspects of the user interface. In particular, we show how the properties of KMS frames—their spatial nature, breadth-first view, homogeneity, small size, etc.—affect the nature of the KMS user interface.