Subject searching is difficult with traditional text-based online public
access library catalogues (OPACs), and the next-generation discovery
layers are keyword searching and result filtering tools that offer little
support for subject browsing. Next-generation OPACs ignore the rich
network of relations offered by controlled subject vocabulary, which
can facilitate subject browsing. A new generation of OPACs could
leverage existing information-organization investments and offer
online searchers a novel browsing and searching environment. This is
a case study of the design and development of a virtual reality subject
browsing and information retrieval tool. The functional prototype
shows that the Library of Congress subject headings (LCSH) can
be shaped into a useful and usable tree structure serving as a visual
metaphor that contains a real world collection from the domain of
science and engineering. Formative tests show that users can effectively
browse the LCSH tree and carve it up based on their keyword
search queries. This study uses a complex information-organization
structure as a defining characteristic of an OPAC that goes beyond
the standard keyword search model, toward the cutting edge of online
search tools.published or submitted for publicatio