Pre-Coordinate Indexing Systems
Pre-coordinate indexing systems are conventional systems mostly found in printed indexes. In this type of system, a document is represented in the index by a heading or headings comprising of a chain or string of terms. These terms taken together are expected to define the subject content of the document. The leading term determines the position of the entry in the catalogue or index, while the other (qualifying) terms are subordinated to it. Let us consider the title of a document "Use of Computers in Library and Information Activities". It might be represented by headings such as:
LIBRARY ACTIVITIES : Use of Computers
COMPUTERS : Use in Library Activities
Since the coordination of terms in the index description is decided before any particular request is made, the index is known as pre-coordinate index. One of the characteristics associated with a pre-coordinate index is that the headings in the index are relatively specific compared to one-concept headings such as LIBRARIES or COMPUTERS. Pre-coordinate indexes are mostly prevalent as printed-indexes. For example, the indexes to abstracting and indexing journals, national bibliographies and subject indexes to library catalogues apply principles of pre-coordinate indexing in varying measures. Such indexes are compiled both manually as well as with the help of a computer.
Two aspects are of great significance in relation to pre-coordinate indexes. The first aspect concerns the consistent description of subjects. In case of subject headings describing many concepts, consistency should be introduced into the terms used to represent individual concepts that constitute the multiple-concept heading. Also, the order in which the individual 'terms representing the unit concepts of a multiple-concept stated must be consistent. Some basic principles have to be evolved and followed regarding an acceptable citation order of the terms. There must be a theoretical basis by which consistent citation orders could be achieved. Use of such theoretical principles may result in the derivation of a structured system of headings with consistent citation order between similar, yet distinct subjects. The citation order is less likely to be over looked if some rationale determines such citation order which is to be followed.
The second significant aspect that requires the attention of subject cataloguers or indexers, is the need to provide access for those users who approach the subject under consideration from one of the secondary concepts. Since only one term can appear in the primary position in the prescribed citation order, the preferred citation order should be the one, which caters to a majority of users. In this context, it may be stated that the same citation order, however well founded it is, will not prove suitable to every searcher. To obviate this problem, references or added entries should be provided in the catalogue or index. At least, one added entry is usually provided for each of the secondary concepts contained in the preferred citation order. Generally, there is some pattern by which such references could be generated to an acceptable level:
Both these aspects arise because of the fact that pre-coordinate indexing systems are basically one-place-systems. That is to say, that these systems normally provide one main entry for each document and are mostly suitable for catalogues and bibliographies. These are very helpful to the searcher since a number of searches can be conducted simultaneously by-tracing entries under similar headings. Pre-coordinate systems find their application in printed indexes and library catalogues.
In summary, it may be stated that in all pre-coordinate indexes, the subject description is composed of a set of terms, which constitutes a summarisation of the subject. Also, the assumption is that subject description reflects the most likely way in which the information concerned will be asked for. Thus, when a user asks for information on a particular compound (multi-concept) subject, the combination of the concepts involved will be easily matched in the index against an entry for the same combination. Because this method of indexing coordinates the elements of compound subjects before any particular request is placed for information on that particular compound subject, it is known as pre-coordinate indexing.