Search (7 results, page 1 of 1)

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Abstract

The PRECIS system of subject headings was designed for use with a computer-produced subject index. Accordingly, the routines of subject heading work are clearly differentiated into clerical procedures and those that require judgement. The clerical procedures can be accomplished largely through the use of computer programs. The subject headings represent a unique combination of several different characteristics. As a result the system permits several coextensive forms of a subject name for each work. The allowable forms of subject name are restricted somewhat by the constraints of the system but the final choice amongst the various alternatives is made by the subject analyst. Often, this choice reflects his or her usage rather than any attempt to realize an explicit code for subject names. There is some evidence that this judgement varies in individual cases. Moreover, there is no empirical evidence that the alternatives permitted do reflect user convenience - although, in fact, this may be true

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Abstract

Designing research on the retrieval effectiveness of computer searches on PRECIS compared with retrieval effectiveness of searches on other types of subject analysis used in computer-based information sources is a complex process. This paper explores the complexity of measuring comparative retrieval effectiveness through a comparison of the subject analysis provided by the PRECIS system for fifty articles with the subject analysis provided for the same articles by three computer-based information sources: ERIC/CIJE, LLBA/Online and PsycINFO. Objectives are: (1) to discover factors that should be taken into account when designing this type of research; and (2) to identify extraneous variables that work against internal validity in research design .

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Abstract

89 articles from a small, Danish left-wing newspaper were indexed by PRECIS and KWIC. The articles cover a wide range of social science subjects. Controlled test searches in both indexes were carried out by 20 students of library science. The results obtained from this small-scale retrieval test were evaluated by a chi-square test. The PRECIS index led to more correct answers and fewer wrong answers than the KWIC index, i.e. it had both better recall and greater precision. Furthermore, the students were more confident in their judgement of the relevance of retrieved articles in the PRECIS index than in the KWIC index; and they generally favoured the PRECIS index in the subjective judgement they were asked to make

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Abstract

Probably the most interesting, original and controversial indexing system of the 1970s has been PRECIS (the Preserved Context Index System) developed by Derek Austin. It attracted such attention that the short courses given at the British National Bibliography offices in London -initiated as a means of teaching the staff of BNB who did subject indexing-were repeated all over the world, in the form of three-day or three-week sessions. A few fortunate non-BNB indexers were taken into London classes, taught by Austin and Digger, and had the advantage of a week's work with the regular staff theresomething that could not be done elsewhere. In addition, descriptions of the system were published from time to time as progress was made an the system itself and clarification or updating were needed. This article has been selected as an example of clarification. A second edition of the original 1974 Manual describing PRECIS appeared in early 1984, so the system may now be regarded as fully mature. PRECIS, which is the culmination of Austin's research for the Classification Research Group plus considerable additional input from the science of linguistics, is a highly sophisticated indexing system, deliberately created to be used with a computer. The motive behind it was that the indexer should do the brain work and the computer the nitty-gritty work of manipulating index terms. Chosen combinations and permutations are used as head words under strict rules to ensure that the context which defines the specific meaning of these words is always present, thus avoiding the ambiguity problem in indexing. The system also has classifi ation features, in part drawn from the Group's long interest in faceted classification. The actual index produces a large number of index entries, each carrying with it the basic context of the item being described. A weIl-defined terminology, in addition to contextdependency, is a feature of PRECIS. Role operators define the types of terms used and control the manipulations of the terms, which are originally entered as a string. The indexer is able to analyze and reduce to string form any document, process, or material that can be described in words, making it ideal for most audiovisual material.
The system itself has two major aspects: - a syntactic approach in which relationships between terms are identified and tagged. Suitable algorithms for manipulation produce a very thorough index in which each head word is kept in context. - a semantic approach in which terminology is weIl defined by ensuring that the relationships of equivalence, hierarchy, and association are clearly established. Charts of relationships are created by inductive means (i.e., from the ground up). A special code for computer manipulation is used with each line of the string. This translates the string format into one that, with specially derived algorithms, can be used by the computer, to produce the actual index headings with all parts rotated by following the algorithm. The PRECIS system has been translated and utilized for languages other than English, notably French, German, and Danish. Modifications needed for idiosyncracies of each language have been made. Some, such as those modifications needed for German, have turned out to have usefulness with English as weIl. All in all, the system has such advanced indexing concepts that it provides a kind of indexing not possible before the computer came into common usage. Austin, who joined the staff of the British National Bibliography in 1963, is currently a member of the British Library staff. His early work included a NATO-sponsored research assignment for the Classification Research Group (q.v.). This, in turn, led to the development of PRECIS.