pre-coordinate indexing V/s post-coordinate indexing
Pre-coordinate Indexing V/s Post –coordinate indexing
--------- --------- --------- --------- ---------- -------INTRODUCTION:
Purpose of all kinds of indexing is the retrieval of information. There are basically two types of retrieval systems.
Pre-coordinate indexing system
Post-coordinate indexing system
Pre-coordinate indexing system
The kind of system in which coordination is done at the time of indexing is called pre-coordinate indexing system. In this system documents or searched under the same terms which the indexer originally assigned to them without any furthers manipulation of terms at the time of searching. It means that whatever compound terms are used they are created at the time of indexing. Rather than at the time of searching. Since co-relations are made during the indexing process and prior to use at the index, it is also called pre-coordinate or pre-correlative indexing.
The subjects represented in pre-coordinate indexes are shown with all of the component concepts coordinated. Thus, the entries in an index based upon pre-coordination are as complex as is necessary to describe the subject. But complex or composite subjects demand a series of entries and terms in order that they are described adequately.
· Chain indexing by S.R.Ranganathan
· PRESIS – preserved context index system by derrick Austin
· POPSI – Postulate based Permuted Subject Indexing by G.Bhattacharya
· SLIC – Selective Listing In Combination by J.P.Sharp
1. Pre-coordinate indexes eliminate the need for sophisticated search logic. The use at the index just looks under the terms that are expects to find the subject described. This is a direct method of search with which users are well acquainted.
2. It requires no special features in their physical format. Almost all printed indexes reflecting pre-coordinate indexing principles, are hard copy.
3. Its principles are applicable to a limited extent in on-line or off-line searched computer based information retrieval systems.
4. These also have found some application in subject indexes to library catalogues and the shelf arrangement of book-stock. These are to be found in abstracting and indexing journals, national bibliographies and indexes to journals.
5. In this single or multiple entry, present certain advantages at the search stage. It is possible for a number of searches to be conducted simultaneously.
1. In pre-coordinate systems, the multidimensional character at the subject matter is forced into a one-dimensional representations, which then necessitates to repeat the index entry in someway for example by rotation of the terms.
2. In this system relationships among topics are built once and for all into the system vocabulary or index entries formed from its components by the indexes. There are nonmanipulative.
3. A multiple access approach is possible, if we enter the document several times in the index by duplicating the citation.
4. These are also criticized on the ground that even the extensive duplication of entries does not provide the true multidimensional retrieval capability to multidimensional subject matter.
5. Efficient approaches to information retrieval demand such systems that permit the free “combination” of classes and the terms representing them.
6. A number of ways have been suggested to provide multiple approach to retrieval in pre-coordinate indexes without complete permulation of index terms.
Post –coordinate Indexing System
As the coordination of index terms in done after the index files has been compiled, this indexing system is called post-coordinate indexing system.
Examples for post-coordinate indexing system:
· Uniterm system of Taube dates about 1951
· Peek- aboo by batter in England and cordonnier in France by 1940.
· Edge- notched card system by calerin mooers
1. None of the entries in the system are specific. There are relatively large number of documents under each heading and if the searches approaches the index as a conventional index, be in liable to become involved in extensive scanning of entries in order to discriminate between relevant and less relevant documents.
2. There are usually a larger number of entries in a post-coordinate indexing system than in an index based upon pre-coordinate indexing principles.
3. The number of different heading is the index is relevant small, because, as in classification a system scheme needless categories or heading than an equivalent enumerative scheme.
Thus in indexing it has pre and post-coordinated indexing system. There have some similarity and dissimilarities. It can be summed up as follows,
· The subject content has to be analyzed and then, the standardized term has to be identified.
· In both types, the terms have to be co-ordinated.
· Both the systems involve the arrangement of the indexed cards in some logical order.
· In input preparation
· Differences in access point
· Differences in arrangement
· Differences in search time
· Differences in browse ability.
1. Rajan T.N. (ed.), Indexing systems; concepts, models and techniques, Calcutta, IASLISC, 1981.
2. Chowdery, G.G. and mahapatra, M, ‘Genesis and scope of faradane’s relational indexing’, librarian, 3, 1988, 10-20.
3. Chowdery, G.G. and Mahapatra, M, ‘Applications of the theory of relational analysis in information retrieval’, journal of library and information science, 14(1), 1989, 1-12.