subject index

from The Free On-line Dictionary of Computing (8 July 2008)
subject index

   <information science> An information resource that contains
   references to other resources, categorised by subject, usually
   in a {hierarchy}.

   {Yahoo} is the most popular {Internet} subject index.  Like
   most other subject indices
   
(http://yahoo.com/Computers_and_Internet/Internet/World_Wide_Web/Searching_the_Web/Web_Directories/),
   Yahoo is arranged {ontologically}.

   Subject indices are not to be confused with {search engines},
   which are based not on subject, but instead on {relevance},
   although (1) this difference is often (possibly rightly)
   hidden from the unsophisticated user, and (2) future
   integration of {knowledge representation} into relevance
   ranking {algorithms} will make this a hazy distinction.

   (1997-04-09)