Consistency in Knowledge Organization

Consistency in knowledge organization means that different actors or indexers describe the same document in the same way. Consistency is a matter of homogeneity in the application of information retrieval languages (or indexing languages).


Lancaster (203, p. 68) introduces the distinction between inter-indexer consistency and intra-indexer consistency. The first term refers to agreement between or among indexers while the second term refers to the extent to which one indexer is consistent with himself. 


While consistency has normally been regarded as an ideal, Cooper (1969) provides some important reservations in relation to this ideal. He demonstrates that indexers that are most consistent with each other do not necessarily produce the best work and that indexing can be consistently bad. While this might seems strange, it is understandable if, for example, indexers have been taught bad principles. Superficial indexing may, for example, rely too much on titles of the documents being indexed. This tends to produce consistent but bad indexing.


The tradition of research in consistency seems to be founded on the assumption that there is an objective optimal indexing and that most indexers are performing close to this ideal. Indexing is not seen as an act in which an indexer chooses some important aspects based on his view and the goals of the specific indexing service. This last view is more related to a hermeneutical interpretation of values and traditions than to a positivist measurement of errors in a system. 


Svenonius and McGarry (1993) conducted research with the hypothesis that there is a “clear-cut right and wrong to LCSH subject heading assignment” at least 80% of the time. In a study of 100 books they found that objectivity in assigning subject headings is possible. Their recommendations to increase subject heading consistency include improving the syndetic structure of LCSH, increasing scope notes, and providing better training and education for subject catalogers.





Cooper, W. S. (1969). Is Inter-indexer consistency a hobgoblin? American Documentation, 20, 268-278. 


Lancaster, F. W. (2003). Indexing and abstracting in theory and practice. London: Facet publishing.(Chapter 5: Consistency of indexing, pp. 68-82 + chapter 6: Quality of indexing, pp. 83-99).


Leininger, K. (2000). Interindexer consistency in PsycINFO. Journal of Librarianship and Information Science, 32(1), 4-8.


Nordström, J. (2005). Indexeringskonsistens: En litteraturgenomgång och en undersökning i LIBRIS (Indexing consistency: A literature review and a study of LIBRIS). Thesis, University College of Boraas, Sweden. Available:


Sievert, M. C. & Andrews, M. J. (1991). Indexing Consistency in Information Science Abstracts. Journal of the American Society for Information Science. 42(1), 1-6.


Svenonius, E. & McGarry, D. (1993). Objectivity in Evaluating Subject Heading Assignment. Cataloging & Classification Quarterly, 16(2), 5-40.


Tonta, Y. (1991). A Study of Indexing Consistency Between Library of Congress and British Library Catalogers. Library Resources & Technical Services 35(2), 177-185.



See also: Representational predictability



Birger Hjørland

Last edited: 27-07-2006