Mediating Interface between Hypertext and Structured Documents

In this paper we describe a unified document model for an authoring system that takes advantage of both hypertext and structured document models: hypertext, which represents a document as a network of information fragments freely referencing one another, helps users create ideas; and structured document models, which represent a document as a rigid tree structure of document components, help users organize documents and make layouts. Our document model comprises the underlying structure and the surface: the underlying structure is a network structure; and the surface is an interface providing a view of the underlying structure. The key features of our document model are: (1) the surface defines tree structures as marked parts of the underlying structure, and maintains consistency between the network and tree structures; (2) the surface monitors users’ walks in the underlying network and marks the trails to define tree structures; and (3) the defined tree structures work as structured documents. Nelumbo, a prototype system, integrates different types of editors that handle features of hypertext and structured documents. Users can choose any of the tools at will, and editing with the tools affects the underlying structure consistently.