Fourth generation hypermedia: some missing links for the World Wide Web

World Wide Web authors must cope in a hypermedia environment analogous to second-generation computing languages, building and managing most hypermedia links using simple anchors and single-step navigation. Following this analogy, sophisticated application environments on the World Wide Web will require thirdand fourthgeneration hypermedia features. Implementing thirdand fourth-generation hypermedia involves designing both high-level hypermedia features and the high-level authoring environments system developers build for authors to specify them. We present a set of high-level hypermedia features including typed nodes and links, link attributes, structurebased query, transclusions, warm and hot links, private and public links, hypermedia access permissions, computed personalized links, external link databases, link update mechanisms, overviews, trails, guided tours, backtracking and history-based navigation. We ground our discussion in the hypermedia research literature, and illustrate each feature both from existing implementations and a running scenario. We also give some direction for implementing these on the World Wide Web and in other information systems. ( 1997 Academic Press Limited