CRANV1P1 Formation of Index Languages chapter Cyril Cleverdon Jack Mills Michael Keen Cranfield An investigation supported by a grant to Aslib by the National Science Foundation. Use, reproduction, or publication, in whole or in part, is permitted for any purpose of the United States Government. -65 - Then, if a request is made for a_b_b, there are the following alternative basic programmes which can be used. (1) Term and species - i.e. ab + aba, abb ... abz[OCRerr] (2) Superordinate - i.e. ab + a (but excluding other subclasses of a; this is how ,generic' search is popularly interpreted in general library practice where a might represent a general treatise on the subject of which a._bb is a subclass). (3) Generic - i.e. a+ aa + aaa, aab ... aaz + ab + aba, abb ... abz + ac + aca, acb ... acz + az + aza, azb ... azz (this is how ,generic' search is normally inter- preted in machine systems and is analogous to search (I) where the content of class ab is taken to include the individually specified subclasses aba, abb, abc ... ). (4)" Coordinate - i.e. a selection of the more likely classes coordinate with a_b_b, e.g. ab + aa + ad; e. g., in a category of three-dimensional shapes a search for Spheroid can be extended generically by searching under Body of Revolution, or by examining all the different kinds of Body of Revolution (Sphere, Hemisphere, Ogive, Cone, etc. ). But some of the latter will be more closely connected to Spheroid than others (e. g. Sphere} and an intermediate search, stopping well short of examining every, species, can be made. It is true, of course, that a 'closer connection' between several sub- classes implies the possibility of an intermediate step of division being inserted. Hut we have to stop somewhere. (5) Subordinate - i.e. a selection of the more likely subclasses of a_bb, e.g. abb + abn. It will be noted that programmes (1), (2} and (3) [OCRerr]re obligatory; no freedom of choice is given to the searcher, but (4} and (5) are permissive, the decision as to the formation of the classes being at the discretion of each searcher. To return to the matter of variations between single-term and concept hierarchies, the shrinking of a concept hierarchy by restricting it to a one-place hierarchy of single terms is seen by the following, which is the schedule given on pages 62-3 and reduced in this way. V] 2 l[OCRerr]xperiment + Experimental V9a/10 Visual + Visualization V11 Spectrography V12 Stroboscopic V13 Shadowgraph V14,16 Photography + Photorecording V17 Schlieren V18 Spark V19 Interferometry V21 Interferogram V23 (Fringe) Shift V24 Strioscopy V25 Interferential V25a Clay V25b China Of the 29 classes in the concept hierarchies only 13 appear in the one-place hierarchy plus two (Interferogram and Lnterferential) which appear for the reasons