"The field of information retrieval focuses on automated techniques, like keyword indexing, for searching large databases."

Library of Congress Subject Headings Example:

Food(May Subd Geog)

 [GN407-GN411.5 (Ethnology)]
 [RA601-RA602 (Public Health)]
 [TX341-TX641 (Home economics)]

UF  Foods
BT  Dinners and dining
		  Home economics
	    Table
RT  Cookery
      Diet
      Dietary
      Gastronomy
      Nutrition
SA  subdivision Food under ethnic groups, 
      and individual animals and groups
      of animals, e.g. Fishes--Food; also
      headings beginning with the word
      Food; and individual foods and 
      beverages, e.g. Bread, Milk
NT  Acorns as Food
      Agar as Food
      Algae as Food
      Animal Food
      Animals--Food
      Aquatic plants as food
      Artificial food
      Baby foods
      Bentu-speaking peoples--Food

The Research Triangle	A Research Worksheet