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62nd IFLA General Conference - Conference Proceedings - August 25-31, 1996

Decomposing DDC Synthesized Numbers

Songqiao Liu
1939 Corinth Ave. #5
Los Angeles, CA 90025
U.S.A.
Tel: (310) 477-9708
Fax: (310) 478-2936


ABSTRACT

Much literature has been written speculating upon how classification can be used in online catalogs to improve information retrieval. While some empirical studies have been done exploring whether the direct use of traditional classification schemes designed for a manual environment is effective and efficient in the online environment, none has manipulated these manual classifications in such a w ay as to take full advantage of the power of both the classification and computer. It has been suggested by some authors, such as Wajenberg and Drabenstott, that this power could be realized if the individual components of synthesized DDC numbers could be identified and indexed. This paper looks at the feasibility of automatically decomposing DDC synthesized numbers and the implications of such decomposition for information retrieval.

Based on an analysis of the instructions for synthesizing numbers in the main class Arts (700) and all DDC Tables, 17 decomposition rules were defined, 13 covering the Add Notes and four the Standard Subdivisions. 1,701 DDC synthesized numbers were decomposed by a computer system called DND (Dewey Number Decomposer), developed by the author. From the 1,701 numbers, 600 were randomly selected fo r examination by three judges, each evaluating 200 numbers. The decomposition success rate was 100% and it was concluded that synthesized DDC numbers can be accurately decomposed automatically.

The study has implications for information retrieval, expert systems for assigning DDC numbers, automatic indexing, switching language development, enhancing classifiers' work, teaching library school students, and providing quality control for DDC number assignments. These implications were explored using a prototype retrieval system.


PAPER

TABLE OF CONTENTS

INTRODUCTION

The Dewey Decimal Classification is used in more than 135 countries, and has been translated into over 30 languages. In the United States, 95% of all public and school libraries, 25% of all college and university libraries, and 20% of special libraries use the DDC. Because it is such an important tool it is necessary to research how it can be used in an online environment. Much literature has been written speculating upon how classification can be used in online catalogs to improve information retrieval. While some empirical studies have been done exploring whether the use of traditional classification schemes is effective and efficient in the online environment, none has manipulated these classifications to take full advantage of the power of both the classification and computer. S ome authors, such as Wajenberg and Drabenstott, suggest that this power could be realized if the individual components of synthesized DDC numbers could be identified and indexed. In my doctoral work I looked at the feasibility of automatically decomposing DDC synthesized numbers and the implications of such decomposition for information retrieval.

AUTOMATIC DECOMPOSITION

Wajenberg is probably the first person who speculated on the potential of synthesized numbers to improve information retrieval provided that the components of synthesized numbers could be recognized. In 1983, he proposed to encode six additional subfields to MARC records to provide necessary information for computers to recognize the components of synthesized numbers. He argued that much more s ophisticated retrieval would be possible if the coding scheme proposed were applied. The approach Wajenberg suggested would work, but it would require a great deal of time and effort for catalogers to analyze and encode components of synthesized numbers. It is not likely that many libraries would be willing to go to this effort considering their rigid budgets and scarce resources. It is even less likely that they would update thousands of, or maybe even millions of, bibliographic records already in their databases.

So it seems logical to ask: can DDC synthesized numbers be decomposed automatically? It would be very significant if they could be because the result could then be applied in any library throughout the world where the DDC is used. In my dissertation study I found out that DDC synthesized numbers could be decomposed automatically. Because of the time restriction here, I will not discuss the stu dy in detail, but briefly describe the algorithms I developed for decomposing DDC synthesized numbers and conclusions of my study.

There are basically two types of rules classifiers use to synthesize DDC numbers: Add Notes and Standard Subdivisions. I examined all the Add Notes and instructions for standard subdivisions in the main class 700 (Arts) and the DDC. The purpose was to classify these Add Notes and Standard Subdivisions into a few categories based on their characteristics and patterns so that the resulting decomp osition rules would be small enough to be manageable and efficient. After examination and analysis, I was able to classify Add Notes into 13 groups and Standard Subdivisions into four groups. I then defined 17 decomposition rules, 13 for Add Notes, and 4 for Standard Subdivisions. The following illustrates a typical decomposition rule:

  • Apply Rule A1: concatenate 704.94 (the number after "the numbers following") and 36 (751.422436 minus 751.4224); match 704.9436 against the Schedule.

  • Retrieve the class 704.9436 (Landscapes).

  • Conclude that 751.422436 decomposes to 751.4224 and [704.94]36.

    I developed a computer system called DND (Dewey Number Decomposer, see Appendix B) to manipulate these algorithms and used it to decompose 1,701 DDC synthesized numbers . From the 1,701 numbers, 600 were randomly selected for examination by three judges, each evaluating 200 numbers. The decomposition success rate was 100% and it was concluded that synthesized DDC numbers can be accurately decomposed automatically.

    Not included in the statistic were forty-two numbers that could not be decomposed. These 42 numbers were sent to the DDC Division of the Library of Congress for clarification. The DDC Division verified that in fact the 42 numbers that could not be decomposed were incorrectly constructed. Although the Dewey Number Decomposer was not designed to detect errors in classification, it seems an extra bonus that it exhibited this unplanned ability to identify incorrect DDC numbers already in the OCLC bibliographic database. Identifying incorrect DDC numbers already in a database as large as OCLC would be a task too monumental to accomplish without computer aid. With the Dewey Number Decomposer , however, we can easily and quickly find out if there are any incorrect DDC numbers in a database that consists of millions of bibliographic records.

    Although I examined only DDC synthesized class numbers in the main class Arts (700), I strongly believe that synthesized numbers in all the DDC main classes can be accurately decomposed automatically, because the synthesizing rules for the Arts (700) are representative of the rules throughout the schedule. Synthesizing rules for the main classes Literature (800) and Language (400) may differ som ewhat from those for other classes. However, I looked briefly at the synthesizing rules for these two classes and believe the differences are not significant and that with some modification or augmentation, the decomposing rules that were defined for the 700ís could be extended to synthesized numbers in all DDC main classes. Nevertheless, a next logical step is to extend and apply the methodolo gy to other DDC classes. Future research on the automatic decomposition of synthesized numbers in the other nine main DDC classes would validate and supplement what I have done so far.

    IMPLICATIONS FOR INFORMATION RETRIEVAL

    Demonstration that it is possible to decompose DDC numbers offers a new perspective on the use of traditional classifications in an online environment. So far, most adaptations of traditional classifications to an online environment have used these classifications in basically the same way as in a manual environment. Now given the possibility of decomposing synthesized numbers automatically and then recombining component numbers in retrieval, there are many other uses to which traditional classifications can be put in the online environment.

    While the chief practical implication of automatic decomposition relates to the retrieval options that can be realized, there are implications also for automatic indexing, switching language development, enhancing classifiers' work, teaching library school students, and providing quality control for DDC number assignments.

    To explore these implications, I created two test bibliographic databases, one with decomposed DDC numbers and the other with synthesized DDC numbers. Both databases were created from 11,662 bibliographic records collected from the OCLC Union Catalog. After removing records containing numbers that were not synthesized or assigned according to 20th edition, 3,749 records remained; this was the nu mber in each of two databases. The DDC numbers were decomposed and, along with pointers to their original records, stored in a separate inverted file for searching purposes.

    The decomposition of DDC numbers can improve information retrieval in a way not possible before by providing multiple access points represented by component numbers and enabling different combinations of component numbers. To illustrate this, I designed a prototype retrieval system utilizing the power of decomposed DDC numbers. Now I will demonstrate a search I performed using the prototype sys tem, which illustrates how component numbers can improve information retrieval.

    Figure 1 is a DDC schedule display. The number to the right is the number of records associated with the class on the left. I was interested in Photographs, so I started my search by selecting the class Photographs from the Schedule Display. At this point, I could either browse titles classed under Photographs or request a display of aspects from which Photographs are treated. Because many ti tles are associated with the class Photographs, as we can see from the number on the right, which is 215, I wanted to improve precision and therefore, I requested a display of aspects to narrow my search. The system then responds with an aspect table of Photographs, again showing the number of associated titles (see Figure 2).

    Because the component numbers are decomposed, the DND can enumerate aspects by which a given topic is treated in a particular database. For instance, in the sample database there is a record with a synthesized DDC number 779.082, which decomposes into 779 for Photographs and 082 for women. When constructing the aspect table for Photographs, the system can use the fact these numbers are associat ed as components and include the aspect Women in the table (see Figure 2). Now, if I select the aspect Women, I will retrieve all records with DDC numbers containing both component numbers 779 for Photographs and 082 for Women. At this point, I have three options:

    1. to browse titles for the selected aspect,
    2. to browse subaspects of the selected aspect, and
    3. to narrow the search with another aspect.

    Suppose I want to find out if the database contains any work on Photographs of the United States; I highlight Historical, geographical, persons treatment (associated with 185 titles) and select the second option. The system responds with a display of subaspects of Historical, geographical, persons treatment (see Figure 3). The same three options as above are provided. I move the cursor to highlight the United States and select the first option, which results in a display of the six titles on Photographs of the United States (see Figure 4).

    Improving retrieval precision using number decomposition could proceed in a number of ways. I could refine the search to retrieve a particular kind of photographs, such as photographs of Men, Animals, Plants, or Landscapes. For example, instead of browsing titles after selecting the United States, I could select the third option to narrow the search with another aspect. After the system respon ds with a list of aspects, I could highlight the aspect Landscapes and then request to browse the titles, which would retrieve three titles on Photographs of Landscapes in the United States (see Figures 5 and 6).

    What this shows is that using the automatic decomposition, it is possible to retrieve a small set of documents consisting of only works on Photographs of landscapes in the United States. Precision of this sort would have been very difficult, if not impossible, without such decomposition. For example, given only synthesized numbers, one would have to search the truncated class number 779 for Photographs, which would retrieve 215 records in the test database, and try to discover those three relevant records by browsing through the 215 records retrieved. One could argue that the truncated class number 779.36 for photographs of landscapes should be searched instead of 779. However, considering that the number 779.36 is a synthesized number itself obtained by adding two class numbe rs together, it is probably safe to say that no one but professional classifiers could perform such a search. Moreover, even such a search like this would still retrieve more irrelevant documents than relevant ones since United States is only one of hundreds of countries covered in DDC. In fact I did perform a truncation search on 779.36 and retrieved 15 records from the test database; as we kn ow only three of them are relevant (see Figure 7).

    In addition to improving precision, decomposition can also improve recall. Supposed that a student of comparative literature wishes a comprehensive listing of works about symbolism in poetry . In a retrieval system using synthesized DDC numbers, for such a listing he has to search the class number 809.1915 for general and comparative studies of symbolism in poetry as well as class numbers for symbolism in poetry in all possible countries, e.g. 811.00915 (for American poetry), 841.00915 (for French poetry), etc. It would be very difficult for anyone to perform this search with a reasonable recall. However, with decomposed numbers, one needs to search only the number 1009 (for history, description, critical appraisal of poetry) or 809.19 and 15 (for symbolism, allegory, fantasy), and all works about symbolism in poetry will be retrieved. This is how the use of component numbers can promote high recall. Also their use makes a search for scattered information much easier and simpler.

    In addition to improving recall and precision, the automatic decomposition of DDC numbers can facilitate retrieval by bringing together related materials through any component number. It has always been a problem in the design of a classification to decide which component or facet is most important when determining citation order. Citation order is the order in which components or facets are se quenced. Normally, in a manual environment only the first facet can be used to bring together related materials. For example, we can retrieve all materials about Photographs through the number 779, because 779 always occurs as the first facet of a synthesized number. However, we cannot easily retrieve materials about a particular country, say, the United States, because the number 73 for Unite d States does not normally occur as the lead facet. Traditionally, it has been assumed that no system can please all the people all the time; all that a system can do is to bring together related materials that fall into the first facet, the one deemed most important by classification designers and, hopefully, also by most users. In this regard decomposition can please all people all the time. With the use of decomposed component numbers, we can either retrieve all materials on Photographs by searching the number 779, or bring together all related documents on the United States by searching the number 73.

    Implications for Automatic Indexing

    Number decomposition also has implications for automatic indexing. To illustrate this, take the synthesized number 327.41052 for foreign relations between Japan and Great Britain as an example. Since the number 327.41052 can be decomposed into three component numbers, 327 for foreign relations, 41 for Great Britain, and 52 for Japan, it is possible to automatically assign caption headings and R elative Index entries, [and terms in various notes] associated with these three component numbers to the documents carrying the synthesized number 327.41052. This would enrich subject access by increasing the number of access points on bibliographic records. Research has shown the need for and the resultant benefits of vocabulary enhancement. In 1985, Drabenstott demonstrated that the terminol ogies in the DDC schedules and relative index, when added to bibliographic records, provide the user with useful subject information.

    Implications for Switching Language Development

    The automatic decomposition of DDC synthesized numbers also has implications for switching language development. In speculating how classification can be used in online retrieval systems, Svenonius (1983) suggests that an important use of classification in online retrieval is as a switching language. She points out that "a classification such as DDC that has already been translated into many la nguages comes ready-made as a switching mechanism." (p. 80) Thus, search terms in one language can be switched through DDC numbers to retrieve documents in several other languages. Although switching can be restricted to the DDC schedules alone, the use of decomposed DDC numbers in switching would provide additional retrieval power. Suppose a user searches international relations between Great Britain and Japan in one language in a retrieval system which contains bibliographic records in many different languages and all the records are assigned DDC numbers. After examining the retrieved documents and associated caption headings for component numbers 724, 41, and 52, the user decides to broaden the search, requesting every document on international relations between Great Britain and any other country in all languages. With the availability of decomposed DDC numbers, the system can respond by simply searching the number 327 for international relations and 41 for Great Britain in all collections. Even for collections not indexed by DDC numbers, switching is possible, since the system can translate from one natural language terminology to another through the DDC numbers 327 a nd 41.

    Implications for Enhancing Classifiers' Work

    Besides decomposing DDC numbers, the Dewey Number Decomposer can also be used by the cataloger to improve his work. For example, after a synthesized number is assigned to a document, a cataloger can ask the Dewey Number Decomposer to decompose the number and show its component numbers and the rules used in decomposition. By examining these the cataloger can then check to see if he has assigned a correct number and covered all important topics dealt with by the work classified.

    Implications for Teaching

    The automatic decomposition of DDC synthesized numbers has implications for improving the teaching of the DDC classification. Although the Dewey Number Decomposer was not designed primarily as a training program, it can be used to train library students in DDC classification. It could do this by showing the steps and rules by which a synthesized DDC number is decomposed, and by presenting DDC r ules in a systematic and organized manner. The Figure 1 shows the Dewey Number Decomposer 's response to a user question about how the synthesized number 796.323640979494 (Los Angeles Lakers) was decomposed. From the explanation, students can learn not only how the DDC number is decomposed but also how the number is synthesized and how to apply Standard Subdivisions and Add Notes.

    Implications for Quality Control of DDC Number Assignments

    Last, but not the least, automatic number decomposition has implications for the quality control of DDC assignments. As we have seen above, the Dewey Number Decomposer can be used to detect errors in DDC numbers assigned to documents, although it is not designed for this purpose. Identifying incorrect DDC numbers in a database such as OCLC would be a task that no one would even think of doing m anually. With the Dewey Number Decomposer, however, it is very simple and quick to find out if there are any incorrect DDC numbers in a database that consists of millions of bibliographic records. As mentioned above, the Dewey Number Decomposer identified 42 numbers that were incorrectly constructed in all records in the OCLC database containing Dewey numbers 700s assigned according to the 20th edition of the schedules. This finding should be of interest to bibliographic service centers that wish to maintain database quality easily and cheaply.

    CONCLUSION

    I believe that a traditional classification scheme such as DDC can be very effective and efficient in the online environment, if we take full advantage of the power of both the classification and computer. I also believe, and my dissertation study has demonstrated that the automatic decomposition of DDC synthesized numbers is possible and has potential benefits in information retrieval, automati c indexing, error correction, and teaching of the DDC classification. I hope I will be able to continue my dissertation work to extend the decomposition rules to the whole schedule.
    
     Appendix A.  Figures
    
      System     Browse     Search      Decompose      Report      Adjust      Quit
    
    DDC Schedule
    
     - Titles,    - Aspects
    _______________________________________________________________________________
      .   Photography and photographs     293
      . . Philosophy and theory     0
      . . Miscellany     5
      . . Historical, geographical, persons treatment     15
      . . Techniques, procedures [formerly also 770.28], apparatus, equipment, materials     1
      . . Special processes     1
      . . Specific fields and special kinds of photography, and related activities     36
      . . Photographs     215
      . Music     540
      . . Philosophy and theory     1
      . . Miscellany     50
      . . Education, research, performances, related topics     31
      . . History and description of music with respect to kinds of persons     28
      . . Historical, geographical, persons treatment     80
      . . Principles, forms, ensembles, voices, instruments     0
    
    Figure 1.  DDC Schedule Browsing, With Photographs Highlighted
    
    
    
    Aspects of Photographs
    
     - Titles,    - Subaspects,    - Another Aspect
    ______________________________________________________________________________
        Historical, geographical, persons treatment	185       
        Other specific subjects	34       
        Landscapes	15       
        Museums, collections, exhibits [formerly also 069.9]	14        
        Animals	10        
        Human figures and their parts	9        
        Women	7       
        Men	6        
        Nudes	5       
        Children	4       
        Architectural subjects and cityscapes	2       
        Plastic arts    Sculpture	1      
        Plants	1      
        Nature and still life	1      
        Jazz. . Principles, forms, ensembles, voices, instruments	1       
        Erotica	1       
    
    Figure 2.  Aspects of Photographs
    
    
    Historical, geographical, persons treatment of Photographs
    
     - Titles,    - Subaspects,    - Another Aspect
    ______________________________________________________________________________
        Persons	128         
        United States	6         
        Metropolitan Toronto	5        
        Union of Soviet Socialist Republics (Soviet Union)####Russia	2         
        Collected treatment	2         
        1980-1989	2         
        1950-1959	2         
        Los Angeles	1        
        Santa Barbara County	1        
        Western United States	1       
        Southwest central counties of Lower Peninsula	1       
        Illinois	1       
        Orleans Parish (New Orleans)	1       
        Birmingham	1       
        District of Columbia (Washington)	1       
    
    Figure 3.  Subaspects of Historical, geographical, persons treatment of Photographs, with United States Highlighted
    
    
    Titles Display
    
    
    Photographs AND United States
    ______________________________________________________________________________
       Best friends : #ba pictorial celebration #cby the winners of
       Between home and heaven : #bcontemporary American landscape
       Measure of emptiness : #bgrain elevators in the American
       Motion and document, sequence and time : #bEadweard Muybridge
       The changing face of America #cPeter C. Jones.
       Typologies : #bnine contemporary photographers #corganized by
    
                             
    
    Figure 4.  Title Display for Photographs of United States
     United States of Photographs
    
     - Titles,    - Subaspects,    - Another Aspect
    ______________________________________________________________________________
        Historical, geographical, persons treatment	185       
        Other specific subjects	34       
        Landscapes	15       
        Museums, collections, exhibits [formerly also 069.9]	14        
        Animals	10        
        Human figures and their parts	9        
        Women	7       
        Men	6        
        Nudes	5       
        Children	4       
        Architectural subjects and cityscapes	2       
        Plastic arts    Sculpture	1      
        Plants	1      
        Nature and still life	1      
        Jazz. . Principles, forms, ensembles, voices, instruments	1       
        Erotica	1       
    
    Figure 5.  Choosing Another Aspect for United States of Photographs, with Landscapes Highlighted
    
    
    
    Photographs AND United States AND Landscapes
    ______________________________________________________________________________
       Between home and heaven : #bcontemporary American landscape
       Measure of emptiness : #bgrain elevators in the American
       The changing face of America #cPeter C. Jones.
       
    Figure 6.  Title Display for Photographs of Landscapes in United States
    
      
    
    779.36?
    _______________________________________________________________________________
     *Between home and heaven : #bcontemporary American landscape
       Desert landscape : #bphotographs #cby Len Jenshel ; [editor,
       Keep it simple : #ba defense of the earth #ctext and
       Light on the land #cphotography, Art Wolfe ; text, Art
       Light on the land #cphotography, Art Wolfe ; text, Art
     *Measure of emptiness : #bgrain elevators in the American
       On second glance : #bMidwest photographs #cby Larry Kanfer ;
       Southern light #cphotography by James Valentine ; text by
     *The changing face of America #cPeter C. Jones.
       V svitlovomu koli #cDavyd Firman = In a circle of light /
       V svitlovomu koli #cDavyd Firman = In a circle of light /
       Wave Hill pictured : #bcelebration of a garden #cby Jean E.
       West coast impressions : #bthe dynamic British Columbia
       Wilderness scenario : #bpeaceful images of the wild #cby Pat
    Figure 7.  Title Display for 776.36?
     
    
      System     Browse     Search      Decompose      Report      Adjust      Quit
    
      
    Figure 8.  Explanation of the Decomposition of 796.323640979494
     Appendix B.  DND Systems Flowchart
     
    DND:  Dewey Number Decomposer
    
    

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