Specificity
Specificity is a property by indexing terms and classification codes. "Apple" is more specific than "fruit" and "025.21 Collection development" is more specific than "025 Operations of libraries, archives, information centers".
The principle of specificity in indexing is in
particular associated with Charles A. Cutter's Rules for a Printed Dictionary
Catalog (1876) and probably no other principle for indexing or
classification has the same amount of acceptance and propagation. Cutter wrote:
"Enter a work under its subject-heading, not under the heading of a class which
includes that subject. EX. Put Lady Cust's book on "the Cat" under CAT, not
under ZOOLOGY or MAMMALS or DOMESTIC ANIMALS".
Balnaves (1976) writes:
"There emerge several inter-related but
distinguishable senses of specificity, which may be summarized as follows:
1. The manner in which one term can be said to be subordinate to, and more
specific than another in a hierarchical arrangement of terms. In this sense,
nothing is said about whether the terms are descriptors or entry terms, or how
they are related to document classes, and no conclusions can be drawn about the
precision or recall capabilities of a system.
2. The extent to which a characteristic which distinguishes a document class is
precisely labeled by a descriptor. In this sense, nothing is said or implied
about the method of indexing, but it is possible to say that, in this sense,
specificity influences precision.
3. The extent to which each descriptor provides direct access to the file for
the class of documents which it labels. In this sense, something is implied
about a method of indexing, for only in certain systems can such directness of
access be achieved, and it can be achieved better in a multiple entry, subject
specification system than in a single entry, document specification system. But
no conclusion can be drawn to the effect that such indexing provides better
precision capability in a system that can be provided by single entry, document
specification indexing.
4. The extent to which each descriptor is a precise and exact label for the
smallest class to which a document belongs. In this sense also, something is
implied about a method of indexing, for only in single entry, document
specification systems is the smallest class identified by intersection of
classes at the point of indexing. But again, no conclusion can be drawn to the
effect that such indexing provides better precision capability in a system than
can be provided by multiple entry, subject specification, combined with class
intersection at the point of search.
5. The extent to which descriptors are assigned to classes to which parts of
documents belong, as well as to classes to which the whole document belongs. In
this sense, nothing is said or implied about a method of indexing, but something
is said about the bibliographic level of indexing, and the effect is rather on
the recall than on the precision capability of the system.
Those appear to be the major uses of the term in the literature of cataloguing
and information retrieval..." (Balnaves, 1976).
Svenonius (1976) operates with the following kinds of specificity: (i) Formal
Specificity; (ii) Extensional Specificity; (iii) Phase-length Specificity; (iv)
Coercive Specificity (v) Componential Specificity; (vi) Consensus Specificity &
(vii) Operational Specificity.
Specificity is often discussed together with the concept " exhaustivity". A
subject analysis of a document is more exhaustive if more of the subjects in the
document is represented by the assigned terms or codes. From experiments with
term-specificity concludes Sparck Jones (1972) that if any research result in
information retrieval is solid, then this must be the improved results gained by
the statistical weighting of terms on the basis of their specificity.
Literature:
Balnaves, J. (1976). Specificity. IN: The Varity of
Librarianship. Essays in honour of John Wallace Metcalfe. Ed. by W. Boyd
Rayward. Sydney: Library Association of Australia. (Pp. 47-56).
Cutter, C. A. (1876). Rules for a Printed Dictionary Catalog. Washington, D.C.: Government Printing Office.
Frâncu, Victoria (2003). The Impact of Specificity on the Retrieval Power of a UDC-Based Multilingual Thesaurus. Cataloging & Classification Quarterly 37(1-2):pp. 49-64. Retrieved 2007-07-24 from: http://dlist.sir.arizona.edu/1880/01/ccq.pdf
Kim, G. (2006). Relationship between index term specificity and relevance
judgment. Information Processing & Management, 42(5), 1218-1229.
Lancaster F. W.
(1986). Vocabulary control for information retrieval. Arlington,
VA: Information Resources Press.
Sparck Jones, K. (1972). A Statistical Interpretation of Term Specificity and its Application in Retrieval. Journal of Documentation, 28(1), 11-21. http://www.soi.city.ac.uk/~ser/idfpapers/ksj_orig.pdf
Spack Jones, K. (1973). Does Indexing Exhaustivity
Matter? Journal of the American Society for Information Science, 24(5),
313-316.
Svenonius, E. (1976). Metcalfe and the Principles of Specific Entry. IN: The Varity of Librarianship. Essays in honour of John Wallace Metcalfe. Ed. by W. Boyd Rayward. Sydney: Library Association of Australia. (Pp. 171-189).
Weinberg, B. H. & Cunningham, J. A. (1985).
The relationship between term specificity in MeSH and online postings in
MEDLINE. Bulletin of the Medical Library Association, 73(4), 365–372.
Retrieved 2007-07-24 from:
http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=227721&blobtype=pdf
Birger Hjørland
Last edited: 25-07-2007