[Sigcr-l] Exhaustivity and specificity of indexing

[Marcia J. Bates]

Dear Colleagues,
	I first saw the discussion of exhaustivity and specificity of 
indexing in Lancaster's 1968 book, Information Retrieval Systems.
	It seems to me that the kind of classification system would 
play a role in dealing with this question of the exhaustivity and 
specificity of classification. Consider a traditional hierarchical 
classification. The classification, if properly designed, is assumed 
to have classes that are "jointly exhaustive" and "mutually 
exclusive."   Thus all the intellectual territory to be classified is 
supposed to be covered jointly by all the classes in the 
classification (jointly exhaustive), and the content of no class 
should overlap with that of any other (mutually exclusive).  In such 
a case, there is one and only one best place in a given 
classification to place a given record.  There is no way to get 
either more exhaustive (one class is the best and only place, so you 
won't assign the record to more than one) or more specific (the 
document is classified in the one best place--there is no way to make 
the class any smaller/narrower.
	Since indexing schemes are now sometimes designed to be 
faceted, and originally hierarchically organized classifications are 
now being at least partially converted to facets--e.g., DDC, there 
has been some blurring.  One can opt to create narrower classes or 
not by utilizing additional facets (DDC, UDC), and records may have 
subject terms from several facets assigned, which the online searcher 
may combine at will.   Under such circumstances, the question of 
exhaustivity and specificity is arguably really about INDEXING 
ASPECTS of the use of classifications--thus the question is part of 
the larger literature of indexing theory.  That may be why you don't 
find it in the classification literature.
				Marcia

-- 
Marcia J. Bates, Ph.D.
Professor Emerita
Editor (with Mary Niles Maack), Encyclopedia of Library and 
Information Sciences
Department of Information Studies
Graduate School of Education and Information Studies
University of California, Los Angeles (UCLA)
Los Angeles, CA 90095-1520 USA
Tel: 310-206-9353
Fax: 310-206-4460
Web: http://www.gseis.ucla.edu/faculty/bates/