Classified Index• is arranged in hierarchy of related topics and working down to the specific.
Advantages conceptually an aid to search.Make searching simple if the users wants to conduct generic searches; since the hierarchy is visually presented.
Disadvantage• A secondary file, an alphabetical list, is necessary, so that a search will generally require two-step procedure of going to the alphabetical list to identify the right position in the classified list.
ExamplesEngineering Index. New York:EngineeringInformation. Inc., 1884- .Index Medicus. Bethesda,Md.:National Libraryof Medicine, 1960- .Index to Theses Accepted for Higher Degreesin the Universities of Great Britain and Ireland. London: AsLib, 1953-.
Coordinate Indexare created by combining two or more single index terms to create a new class.
For example , if the Individual index terms“Black,” “Polecats,” and “Texas” are combined, the result is distinctive class: “Black Polecats of Texas”
A classic example of coordinate index is the marginal –hole punched card system.Index terms were presented by notching out holes in known positions around the card
Marginal-hole punched cardCats Dogs Cows Birdboy, Samel W. Cats and Cows. Journal of Animals, v.2 (Oct. 1990, 1-3)
To Search this type of coordinate index, a needle was inserted through a file of cards at the desired position (e.g., “Cats” and “Dogs”) and the card were shaken so that the notched cards would fall. In this case all cards with notches for cats and dogs would drop out, thus identifying the papers that were indexed under two terms
Coordinate indexing was a natural consequence of the application of the punch-card techniques to information retrieval,since the presence or absence of a hole in a card can represent a binary indication of a specific bit of in information.