NESTED COMPOSITE NODES AND VERSION CONTROL IN AN OPEN HYPERMEDIA SYSTEM

This paper presents a conceptual model for hypermedia systems that, among other features, supports versioning, permits exploring and managing alternate configurations, maintains document histories, supports cooperative work and provides automatic propagation of version changes. In general, the model was designed to minimize the cognitive overhead imposed on the user by version manipulation. The discussion about version control is phrased in terms of the Nested Context Model, but the major ideas apply to any hypermedia conceptual model that offers nested composite nodes. Briefly, nodes that represent versions of the same object at some level of abstraction are grouped together using the concept of version context, support for cooperative work is based on the idea of public hyperbase and private bases, and the problem of version proliferation is addressed using the concept of current perspective. Finally, the paper also presents a generic layered architecture for hypermedia systems with four major interfaces and shows how it matches the conceptual model.