Hierarchical Search Support for Hypertext On-Line Documentation

Abstract Effectively finding relevant passages in a full-text database of software documentation calls for a user interface that does more than mimic a printed book. A hypertext approach, with a network of links among passages, offers great flexibility but often at the cost of high cognitive overhead and a disorienting lack of contextual cues. A tree-based approach guides users along branching paths through a hierarchy of text nodes. The “natural”, sequential implementation of such hierarchical access, however, is psychologically inept in large databases because it is order-dependent, discriminates awkwardly among key terms, clarifies each node's context incompletely, and often involves much semantic redundancy. An alternative, mixed approach, recently implemented in the on-line documentation system at the National Energy Research Supercomputer Center (NERSC), overcomes three of these four problems. It displays only local tree structure in response to “zoomin” or “zoomout” commands issued to focus a search begun with typical hypertext moves. This combination approach enjoys the benefits of cued, spatially interpreted hierarchical search while avoiding most of its known pitfalls. Usage monitoring at NERSC shows the ready acceptance of both zoom commands by documentation readers.