Major traditional library classification schemes
such as UDC, DDC and LCC continue to be widely
used in libraries and some bibliographies and are
being regularly revised. However, they have not
been widely accepted by the digital world of the
Web–Most finding aids to Web resources, resources
in digital repositories, indexes to open access
resources (Directory of Open Access Journals (DOAJ),
Open J-Gate, etc.) depend on keyword indexing.
The application of universal general classification
schemes such as UDC, DDC and LCC appears
to be largely restricted to shelf arrangement of
documents on library shelves (or entries in national
bibliographies). In so far as controlled vocabularies
(verbal indexing languages) are concerned the
idea of a universal thesaurus was probably first
suggested by Soergel in the early 1970s. Following
trends can be seen: