Post combination

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In the post-combination or post-coordination (English postcoordination be) in the documentation , the documentation units are not arranged to open up into a single class, but it will give them a plurality of descriptors allocated. When searching , several descriptors must be combined with one another using logical operators (and, or, not). If the descriptors are systematically related to one another when they are assigned, one speaks of pre-combination, in contrast to post- combination . As a result of the possibility of combining terms, a post-combining classification system, in contrast to a pre-combining system (for example a classification ), manages with a smaller number of descriptors.

Examples

A simple form of post combination is to assign several keywords. Both indexing and syntactic indexing are possible.

scope

With the post combination, only a small number of descriptors are necessary to describe complex facts in relation to the classification. If a document is indexed with an average of 3 descriptors, different combinations can be created with 100 different descriptors .

In practice, however, not all combinations can reasonably be proven. The ratio of required descriptors for a post-combining system in contrast to a pre-combined system is indicated by the combination factor, which is usually in the order of 10 to 100. This means that 100 to 1000 descriptors are sufficient for post combinations, where a classification requires 1000 to 10,000 classes.

advantages

  • The individual descriptors must not disjoint be
  • The number of descriptors is more manageable

disadvantage

If the descriptors are chosen too general, as in the Uniterm system, ambiguities arise in the post combination. For example, the combination "Person" + "Spain" can contain all Spaniards but also other people who are associated with Spain. During pre-coordination , the descriptors are therefore related to each other by assigning roles (see syntactic indexing ), for example "country of birth".

In contrast to a classification, objects made accessible by means of post-coordination cannot be represented completely in an ordered sequence, since they are represented as points in an n-dimensional space, so to speak.

See also

literature

  • Rainer Kuhlen , Thomas Seeger, Dietmar Strauch (eds.): Basics of practical information and documentation. Volume 1: Introductory Guide to Information Science and Practice. Volume 2: Glossary. 5th edition completely revised. KG Saur, Munich 2004, ISBN 3-598-11675-6 .
  • Gernot Wersig : Thesaurus Guide. An introduction to the thesaurus principle in theory and practice. With the collaboration of Petra Schuck-Wersig. 2nd supplemented edition. Saur, Munich et al. 1985, ISBN 3-598-21252-6 ( DGD series 8).

Web links