Synopsis In his paper ‘Subject heading and facet analysis’ (Journal of Documentation. 20(1); 1964, Sep,; P. 109-119) Dr. S.R. Ranganathan demonstrated that the Postulational Approach is a systematic method of arriving at the precise representation of subjects embodied in a document or any other medium. The subject is expressed as a combination of different categories of ideas (Basic subject, Facets, Isolates and Speciators or Qualifiers). Once the verbal expression of a subject is arrived at any scheme for document classification (CC,DDC, UDC or any other ) may be used for assigning the Class Number. Also, the expression of the subject in the verbal plane (in words) can be the basis for the systematic generation of various types of indexes to subjects (Chain index, POPSI, PRECIS, KWAC etc.). The Postulation Approach is anchored on the normative principles and postulates of the General Theory of Knowledge Classification. In this book Dr M.A. Gopinath and Alar Mel Mangai demonstrate, with examples and practical exercises, the application of the Postulational Approach to subject analysis, synthesis and representation and assigning of corresponding class numbers using different schemes of classification (CC ed. 6. and 7.DDC ed, 19,20, and 21 and UDC 4). This book is first of its kind and can be of great help to students of classification, classifiers, teachers of classification, and any one interested in Postulational Approach to Subject Classification in general. Although the examples given are mainly from printed documents, the methodology can be applied to subject embodied in any other medium including digital medium.