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. - 82 - aggregation of attributes, where a term is defined by a number of attributes, each of which reflects a different principle of division of the genus which lies at the heart of the definition, e.g. , Poiseuille flow may be defined as Compressible, viscous, laminar flow between closely parallel planes - and each attribute reflects a different charac- teristic of division for the genus Flow. So where the basic class was Boundary layer flow, for example, related classes brought in by this programme would include Shear flow, Separated flow, Viscous flow, etc. (10) A/Z collateral: the rotated A/Z index of concepts has already been described. This search was made first by examining the index to find the basic class (question concept) and any other concepts containing it (i. e., consisting of the basic class with further qualifications). Those which seemed likely to be relevant were now added to the basic class. For example, to the basic class Axial compressor was added Axial flow compressor blade since this included the basic class and seemed relevant. Or, to Heat transfer would be added such concepts as Convective heat transfer rate, Sur- face subjected to heat transfer, Laminar heat transfer distribution, etc. It may be noted that most of these further classes represent non-generic hierarchical relations of the basic class. Also, that most of the question concepts already consisted of two or more words and that in many cases there would not be any more concepts contain- ing the one sought; e.g., this was the case with Multistage compressor, Non-circular cylinder, Dissociated stream. For those concepts containing more than one word a 'second-level' search was also made, in which each significant word (and any of its adjacent variant word forms) was examined separately and further classes selected from the total body of concepts containing it. For example, to Axial compressor would be added Axial inlet impeller; to Surge line would be added Stall limit line and Surge. It should be stressed that these selections were made in the context of a given complete question and might vary some- what for the same concept if the context differed. For example, in a question on the Surge line of an axial compressor, the 'second-level' for Axial compressor would reject Compressor surge (although it wquld be relevant to the question as a whole) because this approach was already covered by th'e programme for Surge line. Again, [OCRerr] may be noted that many of these further classes represented non-generic hierarchical relations; in addition, the combined first and second level searches generally included those terms selected from generic hierarchies in searches (4), (7) and (9) which also included the actual terms used in the basic concept. (11) Residual hierarchical linkage. The A/Z collateral searches, although providing a large number of non-generic and generic hierarchical linkages, were restricted to those which included one or more of the terms actually used in the question. This still left a number of possibly helpful classes excluded. They could be divided into two groups: firstly all those from the non-generic hierarchies which appeared in the schedules where the question concept (the basic class) was located, but which failed to include the actual question term or terms (in which case the A/Z collateral would have disclosed them. ) It was a simple matter to establish these, by scanning the various facets subordinated to a given concept, or adjacent to it. Secondly, all related classes not already disclosed by the hierarchical relations of the ten searches described. A number of these were already provided for in the schedules, by references; e.g., Surface combustion (D66) see also Ablation; Vaneless diffuser (in compressors) (F84) see also Ducts; Compressor surge see also Rotating stall; Mass flow fluctuation (U44) see also Sound waves.