Fig. 2. Dewey Edition 21 Education Outline
- 1. Adult Education
- 2. Alternative
- 3. College Entrance
- 4. Community Colleges
- 5. Companies@
- 6. Conferences
- 7. Courses
- 8. Databases
- 9. Educational Standards and Testing
- 10. Environmental Education@
- 11. Financial Aid
- 12. General Information
- 13. Government
- 14. Grants
- 15. Guidance
- 16. Higher Education
- 17. Institutes
- 18. Instructional Technology and Training
- 19. Interest Groups@
- 20. Journals
- 21. K12
- 22. Languages
- 23. Lectures
- 24. Libraries@
- 25. Literacy
- 26. Math and Science Education
- 27. News
- 28. Magazines@
- 29. Online Teaching and Learning
- 30. Organizations
- 31. Products@
- 32. Programs
- 33. Social Studies
- 34. Special Education
- 35. Teaching
- 36. Television
- 37. Universities
- 38. Vocational Schools
- 39. Workplace
DDC and LCC Have a Hierarchical Structure
Williamson points out that:
Hierarchical relationships are the essence of all classification. Enumerative classifications systems provide a systematic arrangement of subjects according to set of principles based on an accepted philosophy of the organization of knowledge, on patterns established on the basis of literary warrant, and frequently, on a combination of both. However, classified order is not self-evident. Some method or device is required to preserve the relationships among classes, subclasses, topics and subtopics. In some classification systems, for example DDC, these relationships are preserved and may be manipulated through the hierarchical notation. LCC does not fit this pattern. Its notation preserves order but does not reflect hierarchy. ... some other means must be found to preserve those relationships.
In DDC, the sequence of subjects from general to specific, is indicated by the number of digits that form the DDC number. For example, when the DDC number 663.223 for the topic "making of red wine" is shown in the context of its Dewey hierarchy it can be seen that "White Wine," "Red Wine," and "Sparkling Wine" are at the same hierarchical level. The DDC number 663.22 corresponding to the heading "Specific kinds of grape wine" is one digit shorter than those used to indicate exact kinds of wine and is considered to be broader or superordinate to those with longer numbers. Indentation is also used to indicate hierarchy. Through both notation and indentation, this example shows that each topic except for the main class 600 Technology is subordinate to and part of all the broader classes above it.
600 Technology (Applied sciences) 660 Chemical engineering and related technologies 663 Beverage technology 663.2 Wine and wine making 663.22 Specific kinds of grape wine 663.222 White wine 663.223 Red wine 663.224 Sparkling wine
In both the LC Classification and in Yahoo's category trees, hierarchy is indicated by the indentation of category or class labels. To illustrate, consider the following class numbers and headings listed in the LC Classification QA schedule:
QA76.33 Computer Camps QA76.38 Hybrid Computers QA76.4 Analog Computers QA76.5 Digital Computers
Given only the notation (class numbers) and captions (headings), it is unclear what relationship exists among the ordered classes. When these classes are placed in the context of the LCC hierarchy structure in a display similar to what is found in the printed schedules, the indentation clearly indicates that Hybrid, Analog, and Digital computers are the same level of hierarchy and that QA76.33 is a subcategory under study and teaching and not a type of hybrid computer.
QA71-QA90 Instruments and machines QA75-QA76.95 Calculating machines QA76 Electronic computers. Computer Science QA76.27 Study and Teaching QA76.33 Computer Camps QA76.38 Hybrid Computers QA76.4 Analog Computers QA76.5 Digital Computers
Yahoo subcategory trees also use indentation to indicate hierarchy. For example, the following hierarchy is found under "Computers and Internet"
Computers and Internet
Internet
Entertainment
Interesting Devices Connected to the Net
Spy Cameras
Indoor Cameras
Outdoor Cameras
Pets@
Aquariums
The preceding examples demonstrate that both Internet classification schemes and library classification schemes provide hierarchical structures capable of supporting topic browsing. Library schemes would seem to have some advantage over Internet-based schemes because they are accompanied by notations that facilitate the manipulation of class relationships. Recall that DDC's notation can be used to navigate broader, narrower, and coordinate relationships among classes, while LCC's can be used to arrange related topics in order. Yahoo's hierarchy structure requires encoding to take advantage of relationships among classes. Links to other subject-oriented schemes
Library classification schemes are generally considered to be retrospective: classes are added or revised only after sufficient literary warrant is demonstrated and classes are removed with even greater caution. For these reasons much greater attention needs to be given to employing the implicit and explicit links between library classification systems and other subject oriented schemes. For example, Electronic Dewey, the electronic version of DDC20, includes a statistical mapping from the OCLC Online Union Catalog of up to five of the most frequently used LCSH to each Dewey number. This Electronic Dewey feature, which has been well received by users, provides additional indexing terms to lead users to appropriate topic areas in Dewey. In addition to statistical mappings, the Electronic DDC21 database will include many DDC/LCSH links that have been reviewed editorially. Links similar to those made in Electronic Dewey can be made for LCC and LCSH by processing the in bibliographic records containing fields for both. For LCSH and LCC explicit links are also available in LC Subject Authority records that contain LC classification number fields. In an analysis of the LC Subject Authority file, Vizine-Goetz and Markey found that about 43% of topical subject heading records (MARC tag 150) contain LC classification number fields. Science and technology classes account for almost half (47.72%) of the LC class numbers.
In addition to providing supplemental vocabulary for topics already represented in class schedules, linking DDC, for example, with other subject thesauri provides a mechanism for allowing new topics to be represented in the classification even if each is not supplied with its own number. For example, the LC subject heading Microsoft Network (Online service), listed among the "Subject Headings of Current Interest" in CSB, No. 70 (Fall 1995), can be linked to (among others) DDC number 025.04 "Automated information storage and retrieval systems" and to DDC number 004.678 "Internet." This subject heading, however, has been assigned to only four LC MARC records with DDC number 025.04 and therefore may not be among the top 5 LCSH statistically mapped to this number. The ability to map current terminology into DDC and LCC is particularly important if library classification is to be used to provide access to Internet resources.
Links to Editions in Other Languages
Classification experts have long recognized the potential of DDC to serve as a mechanism for switching between languages. With the recent publications of DDC in French and Spanish and with a Russian translation scheduled for publication in December 1997, it may now be possible to realize this capability.
Table 2 shows DDC captions in English, French, and Spanish for three DDC classes on the topic microcomputers. Captions and relative index terms in translation databases could be used to provide a multilingual subject browser to a database of Internet-accessible resources that have been assigned DDC numbers, such as OCLC's NetFirst database.
Table 2. DDC Captions
DDC Class English Spanish French
Number 004.1 General works on Obras generales sobre Ouvrages généraux sur specific types of tipos específicos de les différents types computers computadores d'ordinateurs 004.16 Digital microcomputers Microcomputadores Micro-ordinateurs digitales 004.165 Specific digital Microcomputadores Micro-ordinateurs microcomputers digitales específicos particuliers
Library Classification or Internet-based Schemes?
This paper examines several characteristics of DDC and LCC classification schemes that make them suitable for providing subject access to Internet resources. To review, DDC and LCC are
- General classification schemes, with
- hierarchical structures and notation that orders classes
- They contain links to other subject schemes, and
- links to translations in other languages (presently DDC only)
Despite these favorable properties additional improvements are needed if online classification data is to be used as a major tool for providing online subject access to traditional collections as well as to Internet-accessible resources. The following improvements are recommended:
- Evaluate DDC and LCC captions for expressiveness and currency
- Decompose and code class number components to identify the specific subject and aspects represented
- Continue to add new terminology as index terms even if each is not supplied with its own number
- Expand links to other controlled vocabularies
- Expand definitions of literary warrant to include Internet resources
- Build demonstration systems
Recommendations 1 and 2 are not new. Over ten years ago, Karen Markey advocated similar improvements be made to the DDC to facilitate its use in online catalogs. Arnold Wajenberg (1983) proposed a scheme for encoding DDC numbers to enhance automated subject retrieval . Fortunately this time, there appears to be both interest and resources to make needed enhancements to online classification data. For example, a project has been established to transform captions in the 1000 DDC summaries (the first three digits in Dewey) into end user language [DDC ALA Midwinter Conference Report, January 1996; http://www.oclc.org/oclc/fp/news/9602ala.htm]. The recast summaries will be used in the prototype of a Dewey-based subject browser for the NetFirst database of Internet-accessible resources. While a good first step, it will be necessary to look well beyond the first three levels of Dewey to captions at lower levels of the DDC hierarchy since many of the DDC numbers assigned to NetFirst records extend four or more digits past the decimal point. These efforts will advance recommendations 1 and 6.
In the context of DDC, work on recommendations number 3 and 4 is also underway. Dewey editorial staff and OCLC research staff are collaborating on projects to enhance the electronic version of the Dewey editorial database with selected LC subject headings from the Weekly Lists and headings with high postings in the OCLC Online Union Catalog database. Editorial staff will also add coding to the Editorial Support System database to indicate links between Dewey Relative Index terms and LCSH and Sears headings. For LCC, the LC Cataloging and Policy Support of Office is reviewing the index structure of the LCC schedules and is consulting with classification expert Lois Chan on the design of a combined index to LCC. It is very likely that this work could lead to future efforts to form better links between LCC and LCSH.
The projects described above indicate a commitment by the owners and maintainers of DDC and LCC to improve these systems for automated subject retrieval. If Internet resource catalogers display a similar commitment to assigning class numbers to the bibliographic records they create, online classification data can form an important bridge between library methods for organizing materials and Internet-based techniques for accessing electronic collections. Furthermore, DDC and LCC based interfaces will provide users with a common interface to traditional and electronic libraries.
References
Chan, Lois Mai, John P. Comaromi and Mohinder P. Satija. 1994. Dewey Decimal Classification: a practical guide. Albany, N.Y.: Forest Press. p. 6.
Finni John J. and Peter J. Paulson. 1987. "The Dewey Decimal Classification enters the computer age: developing the DDC database(TM) and Editorial Support System." International Cataloguing 16 (4 ):46-48 (October/December 1987).
Guenther, Rebecca S. 1992. "The Development and Implementation of the USMARC Format for Classification Data." Information Technology and Libraries 11 (2):120-131 (June 1992).
Markey, Karen, and Anh N. Demeyer. 1986. Dewey Decimal Classification Online Project: Evaluation of a Library Schedule and Index Integrated into the Subject Searching Capabilities of an Online Catalog. Dublin, Ohio: OCLC Online Computer Library Center, Inc., Office of Research .
Svenonius, Elaine. 1983. "Use of classification in online retrieval." Library Resources and Technical Services 27(1):76-80 (Jan./Mar. 1983).
Vizine-Goetz, Diane and Markey, Karen. 1989. "Characteristics of Subject Heading Records in the Machine-Readable Library of Congress Subject Headings." Information Technology and Libraries 8(2): 203-209 (June 1989).
Wajenberg, Arnold S. 1983. "MARC Coding of DDC for Subject Retrieval." Information Technology and Libraries 2(3): 246-251 (September 1983).
Williamson, Nancy J. 1995. The Library of Congress Classification: a content analysis of the schedules in preparation for their conversion into machine-readable form. Washington, D. C.: Library of Congress, Cataloging Distribution Service. p. 17.
Acknowledgments
The author is grateful for the valuable comments of Joan S. Mitchell, Editor Dewey Decimal Classification and is also grateful for assistance from Barbara A. Brownell, Technical Processing Specialist, OCLC.
Appendix
A. Yahoo Education Topics
B. Infoseek Education Topics
