Library and Information Science

In this article the dyadic organization of subject headings means composing subject headings of descriptors in pair. From the view-point of dyadic organization the writer examines and compares such systems as Medical Subject Headings, Permuterm Subject Index to Science and Technology and SYNTOL, trying to clarify the characteristics of subject headings in each. The writer then explains about the nature of his own system called CONCODE (Contextual Connection of Descriptors) which combines descriptors by conjunctive marks and prepositions. The dyadic organization principles are applied to CONCODE, providing headings with inclusiveness and CONCODE with exclusiveness. Although in information retrieval recall and relevance factors are said to act contrary, the writer tries to raise the two factors simultaneously by the combined use of dyadic headings and CONCODE.