CORRELATIVE INDEXES II: CORRELATIVE TROPE INDEXES

CHARLES L . BERNIER*

The first paper in this series (1) described a technique for the conversion of manipulative correlative indexes of various forms into non- manipulative correlative indexes in book or card form. A discussion of the problem of bringing pertinent vocabularies of searcher and documentation system into coincidence and that of generic searches was left to this paper which reports studies of several approaches to the solutions.

It is interesting to examine more closely the most promising of these approaches to the problem of bringing pertinent vocabularies into coincidence - namely, that of using a relatively small vocabulary of terms of a generic nature. The use of a vocabulary of generic, rather than specific, terms for indexing might be called generic trope indexing. Rhetorical tropes, in which words or expressions are used in senses different from those which properly belong to them, may offer a way of reducing the number of terms in the vocabulary of an indexing sys- tem for a large collection of documents, etc., to such a size that all relevant terms can be read or located readily. For this purpose, the tropes of metonymy, synecdoche, and irony seem most useful. The use of terms repre- senting the genus, o r the whole, in place of terms for the species, or part, can be used to reduce the number of terms needed in the vo- cabulary.

The occasional use of tropes (or rhetorical devices which closely resemble tropes) in al- phabetical subject indexes is well established. The indexing of ‘pH”, for example, under ‘Hydrogen-ion concentration’ seems to repre- sent the tropes of metonymy and irony com- bined. ’pH,” being the logarithm of the recip- rocal of the hydrogen-ion concentration, makes its inclusion under the latter term seem like the use of metonymy. The fact that as the hydrogen-ion concentration increases, the pH decreases, makes their combination under one

*Chemical Abstracts, Columbus, Ohio

heading seem like the trope irony in which the negative concept is expressed as positive or the reverse. The indexing of ‘calculus” under ‘Mathematics” seems like the use of synec- doche. Zator documentation systems (2) find use for tropes in the selection of ‘descriptors” for these manipulative indexes. The use of the descriptor “aircraft”, for example, to designate ‘airplanes, balloons, helicopters, rockets, guided missiles” (3) seems like synecdoche.

If the number of terms in the vocabulary of a documentation system can be kept small enough so that all can be read in a reasonable length of time, and if correct selection can be made by this reading, then the problem of bringing vocabularies into coincidence and that of the generic search seem well on the way to- ward solution.

Subject indexes currently published depend on: (1) internal cross references, (2) sugges- tion of new te rms by words found in modifying phrases under headings, and (3) principally on the background and development of the searcher to bring vocabularies into coincidence. The searcher is expected to grow in his search (4,5) and to be aided by his vocabulary. Courses of study, textbooks, dictionaries, published ar- ticles, systems of nomenclature, conversation with colleagues and experts, compendia, glos- saries, thesauri, and the like, give the searcher a vocabulary with which to approach the index. The index-searching process, together with reading of the references discovered, becomes an education in the terminology of the field of interest. The new terms discovered and the old terms re-defined more precisely are then re- applied to the index to discover further refer- ences, and so on. Eventually all relevant ref- erences will be discovered. It now seems possible to hasten this process of bringing vo- cabularies into coincidence by keeping the vocabulary so small, or organizing it in such a way, that all terms can be located before the

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48 A M E R I C A N D O C U M E N T A T I O N

search is undertaken, The possible success of this approach is made to seem more likely by the success of Zator documentation systems (3), some of which employ vocabularies of but 250-400 terms for retrieval from collections of many thousands of documents. Other clues to possible success from this approach a re to be found in the relatively small vocabularies of Basic English (6) and in isolating languages such a s Chinese. Selectivity is achieved in these systems by correlation of terms. The more terms taken simultaneously the greater the specificity and selectivity. If the trope vo- cabulary of an index to a collection of docu- ments were to contain more than a few hundred terms, then some form of organization would almost certainly be necessary to save reading time. The reading of a thousand or more te rms for each search would probably make a system using this technique impracticable for the oc- casional user. The constant, o r professional, user would doubtless soon memorize a vocab- ulary of even several thousand terms.

A limited thesaurus would seem to be an- other effective way of bringing the relevant terms to the attention of the searcher if the vo- cabulary proves too large to be read completely each time for selection. Correlative-index terms found in the thesaurus could for example, be designated by an asterisk. The use of syn- detic devices, such a s cross references, in the vocabulary is another method of aiding the in- dex user to find all pertinent terms.

A different approach to the problem of vo- cabularies is the construction of a comprehen- sive thesaurus (7) for all terms in the field of the correlative index. The construction of such a thesaurus for even one field of science, such as that of chemistry, would present some major problems which could perhaps best be solved by a large lexicographic organization. The pro- vision of a limited thesaurus, as mentioned above, for a relatively small vocabulary would present a much smaller problem. The com- prehensive thesaurus will be discussed in the following paper.

Of the rhetorical tropes, the use of synec- doche, in which the generic term replaces the specific, seems the most promising way of re- ducing the size of the vocabulary. The term “trope indexing” can be defined a s the use of rhetorical-trope terms a s index headings. The use of terms in senses not properly belonging to them is the principal feature of this kind of indexing. By way of contrast, subject indexes

usually avoid trope terms and employ a s head- ing te rms those of maximum specificity in the field covered. For example, “2-Butene” would usually be subject-indexed under this heading rather than under “Olefins”. However, fo r fields of subject matter somewhat removed from the principal field of the index, it is often the practice to use the more general headings for the specific. A s mentioned above, “calcu- lus” might be indexed under “Mathematics” in a chemical index. This seems to be a form of synecdoche in which the generic term is sub- stituted for the specific. Another way of view-

ing this last example is that “calculus” is calssified under “Mathematics”. In standard subject indexes negative statements a r e fre- quently omitted in the modifying phrases under headings so that a positive statement results instead. This amounts to the use of the trope, irony, in which the opposite was expressed. An example of this would be the index entry, “Vi- tamin B,, effect on blood sugar”, which would be used to index the fact that there was no ef- fect on blood sugar.

If limitation of the number of terms in the vocabulary were no object, then tropes other than generic synecdoche might become domi- nant. It is easily conceivable that metaphor, or the reverse, could be the dominant trope in the indexing of poetry. For example, “silvery bark on a velvet sky” might be indexed, among other things under ‘Moon.”

In the building of a correlative index which uses tropes for vocabulary control, there arises the problem of selecting the vocabulary terms. Selection can probably best be done on a logical- empirical basis during the indexing process. Control of te rms can be made during the index- ing and during the index editing. If it is found that too many documents a re being associated with one term, then more specific te rms can be substituted. If too few documents a r e being in- dexed by a term, then a more generic term can be used. It is important to note that these changes can be made during the editing of a nonmanipulative index as well a s during the in- dexing. In such a nonmanipulative index, as was mentioned in the first paper, unpermuted terms can be included to give greater selec- tivity of documents without increasing the s ize of the vocabulary. The use of unpermuted terms is another method of vocabulary control. These unpermuted terms can be alphabetized along with the permuted terms, but they will not appear as the f i rs t term in an entry. Selectivity

CORRELATIVE INDEXES II 49

greater than that provided by simple correla- tion of vocabulary terms can also be provided in other ways.

If too many undifferentiated entries a r e found under certain combinations of vocabulary terms in the index, then adequate differentiation can probably be supplied by including the title of the document, in the index, in addition to the permuted terms. A more expensive but more effective method of providing extra selectivity would be to include specially composed modify- ing phrases to accompany each undifferenti- ated entry. These titles o r special modifica- tions would, of course, be unpermuted and independent of the trope vocabulary. If too many undifferentiated entries were found in the editing of the correlative index, it would most probably indicate that the te rms chosen were too general o r too interrelated. The vocabulary of terms for generic-trope indexing would be flexible and could be changed somewhat from year to year. There would seem to be no prob- lem of obsolescence. If a given document could not be indexed adequately by terms in the exist- ing vocabulary, then one o r more new te rms would be added. The indexing could be done most easily by check marks placed beside as- sociated terms printed on sheets containing complete vocabularies. One vocabulary sheet would be used per document indexed. The terms checked would be transcribed in par- tially permuted alphabetical order onto cards which would then be alphabetized and used for compiling the index.

Al l of these approaches to vocabulary con- trol require further research, especially for collections containing one hundred thousand o r more items. Correlative trope indexing needs study to determine the size and growth of the vocabulary as well as the most effective methods of control. It is, indeed, possible that interlocking of meanings of vocabulary te rms for a large field would be found to reduce se- lectivity of documents to such a point that cor- relative indexes - both manipulative and non- manipulative - would be impracticable except for aiding very broad, generic searches. An example of the interlocking of meanings in re- ducing the selectivity of vocabulary terms would occur if “plant”, “insect”, “control”, and “agent” were terms in the vocabulary of a cor- relative index. In this case it would require these four terms used in correlation to select all studies of insecticides related to plants. “Interlocking of terms” may be a rather poor

way of describing the phenomenon. Knowledge does not grow uniformly in all directions. New fields attract immediate study and the l i tera- ture grows disproportionately, often in unpre- dictable directions. This sudden and unexpected growth in certain directions makes the more general vocabulary inadequate to handle the in- creased detail. One obvious answer to the problem illustrated by the above example i s to use, as a vocabulary term, “Insecticides”, in place of three of the terms: “insect”, “control”, and “agent”. However, what i s to become of the old terms upon the introduction of the new term “Insecticides” is not entirely clear. One possibility i s to instruct the searcher of the correlative index always to use the term em- bodying, in meaning, as many of the other te rms as possible, and to avoid component te rms in searching. Whether such a solution would be generally effective will require further study.

It i s interesting to investigate the results of varying the parameters of possible correlative indexes using generic tropes, together with modifying phrases, for vocabulary control. As the generality of index-vocabulary te rms i s increased, the number of te rms in the vocabu- lary, for a given field, will decrease. The number of differentiating modifying phrases for index entries must then be increased to main- tain selectivity. As one approaches the limit of variation in this direction, one reaches a stand- ard alphabetical subject index for a specific field. There would be but one generic-trope term - “chemistry”, for example - and the in- dex would be a subject index for the field of chemistry. Before this limit i s reached, the correlative index would become, in effect, a classified subject index in which the searcher would have the opportunity of generating any class he wished to search, from the combina- tions of terms which he found in the trope vo- cabulary. The necessary selectivity would be provided, in each of these classes, by modifying phrases appropriate to each combination of terms and document. In the other direction, the specificity of vocabulary t e rms and, conse- quently their selectivity, would be increased. In this case the need for unpermuted modifying phrases would be reduced so that such a non- manipulative correlative index would come eventually to resemble a subject index without morphemes. The increased s ize of the vocab- ulary required to provide adequate selectivity in thislast case would probably make syndetic de- vices, such as cross references, classifications,

50 A M E R I C A N D O C U M E N T A T I O N

or thesauri necessary. At the present, there would seem to be some optimum level of gen- erality of generic-trope terms for the vocab- ulary of an alphabetical correlative index. It also seems likely that this level would not be critical, because of the availability of compen- sating factors. Whether these last two hypoth- eses a re true, and the relationship between degree of generality and size of field (number of documents) remain to be determined. As the size of the field is increased, the size of the vocabulary a t a given level of specificity will probably also increase. If the field deals with research, there will be a more rapid change of terms in the vocabulary than otherwise would be true. Just how rapid a change of terms can be assimilated for effective use in correlative indexing, especially if collective or cumulative indexes a re necessary, is another problem to be solved.

It should be noted also that all of the prob- lems described in this contribution are associ- ated equally with punched-card systems, coordinate indexing, etc., a s well a s with non- manipulative correlative indexes and standard subject indexes. The problems relate, in the main, to vocabulary and a r e almost entirely unaffected by the mechanics of the systems. Since all of these document-searching systems require a vocabulary from which selection is made, the problem is ubiquitous. It i s likewise immaterial if the vocabulary of the system i s explicit, implicit, or a combination of both. If suitable solutions to these problems are not possible for large collections of documents, then all of the systems probably will be found

ineffective for complete and generic searches on a large scale. Preliminary tests confirm the results obtained by others for relatively small fields of knowledge-that is, trope in- dexes a r e successful,

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Bernier, Charles L., “Correlative In- dexes. I. Alphabetical Correlative In- dexes”, American Documentation, V. 7, (October 1956), pp. 283-288. Mooers, Calvin N., “ Zatocoding Applied to Mechanical Organization of Knowl- edge”, American Documentation, V. 2,

Mooers, Calvin N., “A New Semantic Principle in Information Retrieval Sys- tems”, A paper presented before the American Documentation Institute, No- vember 5, 1954. Crane, E. J., and Bernier, Charles L., Indexing and Index Searching”, p. 347, Chapter 23 in, Casey, R.S. and Perry, J.W. Punched Cards. Their Applications to Science and Industry, New York, Reinhold, 1951. Bernier, C. L., and Crane, E. J., “Indexing Abstracts”, Industrial and Engineering Chemistry, V . 40, (1948) p.730. Ogden, C. K., The System of Basic Eng- lash. New York, Harcourt, Brace and Company, 1934. Reference 5 above, p. 729.

(1951) pp. 20-32.