• Library classification systems; semi-automatic
indexing systems;
• Keyword indexing-based on H.P. Luhn’s experiments
widely adopted by bibliographic databases, online
retrieval systems and Web search engines; The
techniques coming under this broad category
are being continuously refined to improve the
quality of indexing/metadata extraction using
developments in text processing and a variety
of statistical techniques;
• Pre-publication metadata (based on e.g., Dublin
Core or some other schemes) by the author/
publisher to enable service providers to more
accurately identify the class(es) to which a
resource belongs.