Semantic linking has always been a strand of hypermedia research and is becoming central to current attempts to facilitate access to information in large hypertexts and the emerging 'semantic web' [Berners-Lee 1998a]. Due to the scaling problems with explicitly authored links between information items, it is likely that future large scale hypertexts will employ a mixture of authored links and indirect, computed links via some form of indexing system. Problems of information access are heightened by the lack of precision of current WWW retrieval technology and users unfamiliar with indexing conventions. There is a critical need for tools that will assist users to formulate and refine queries, and navigate through information spaces. Recent years have seen the growth of metadata, Digital Libraries, and interest in the application of traditional information science and library cataloguing techniques to the new environment of hypertext and the WWW. Semantic indexing provides a bridge between the various information disciplines. With the growing influence of the Resource Description Framework [Lassila 1999], semantic tagging and cataloguing of information is likely to become a key component of the information architecture of intranet hypertexts and the WWW.