Full report

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NASA / TM-1998-208955 Creating A Canonical Technical Information System for NCSTRL+ Melissa £ _Jfany Coi_p_ier Sciences Corporalion, Hai_pion, Michael L. Nelson Lansleli Research Cenier, Hampion, _'rsinia December 1998 Scientific and Classification Virsinzh

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The NASA STI Program Office ... in ProfiIe Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA's scientific and technical information. The NASA STI Program Office provides access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office is also NASA's institutional mechanism for disseminating the results of its research and development activities. These results are published by NASA in the NASA STI Report Series, which includes the following report types: TECHNICAL PUBLICATION. Reports of completed research or a major significant phase of research that present the results of NASA programs and include extensive data or theoretical analysis. Includes compilations of significant scientific and technical data and information deemed to be of continuing reference value. NASA counter-part of peer reviewed formal professional papers, but having less stringent limitations on manuscript length and extent of graphic presentations. TECHNICAL MEMORANDUM. Scientific and technical findings that are preliminary or of specialized interest, e.g., quick release reports, working papers, and bibliographies that contain minimal annotation. Does not contain extensive analysis. CONTRACTOR REPORT. Scientific and technical findings by NASA-sponsored contractors and grantees. CONFERENCE PUBLICATION. Collected papers from scientific and technical conferences, symposia, seminars, or other meetings sponsored or co-sponsored by NASA. SPECIAL PUBLICATION. Scientific, technical, or historical information from NASA programs, projects, and missions, often concerned with subjects having substantial public interest. TECHNICAL TRANSLATION. Englishlanguage translations of foreign scientific and technical material pertinent to NASA's mission. Specialized services that help round out the STI Program Office's diverse offerings include creating custom thesauri, building customized databases, organizing and publishing research results ... even providing videos. For more information about the NASA STI Program Office, see the following: • Access the NASA STI Program Home Page at http.'//www.stLnasa.gov • E-mail your question via the Internet to help@sti.nasa.gov • Fax your question to the NASA Access Help Desk at (301) 621-0134 • Phone the NASA Access Help Desk at (301) 621-0390 Write to: NASA Access Help Desk NASA Center for AeroSpace Information 7121 Standard Drive Hanover, MD 21076-1320

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NASA/TM-1998-208955 Creating A Canonical Technical Information System for NCSTRL+ Melissa £ _Jfany Coi_p_ier Sciences Corporalion, Hai_pion, Michael L. Nelson Lansleli Research Cenier, Hampion, _'rsinia National Aeronautics and Space Administration Langley Research Center Hampton, Virginia 23681-2199 December 1998 Scientific and Classification V#sinzh

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Available from the following: NASA Center for AeroSpace Information (CASI) 7121 Standard Drive Hanover, MD 21076-1320 (301) 621-0390 National Technical Information Service (NTIS) 5285 Port Royal Road Springfield, VA 22161-2171 (703) 487-4650

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Creating a Canonical Scientific and Technical Information Classification Melissa E. Tiffany Computer Sciences Corporation NASA Langley Research Center MS 157D Hampton, VA 23681 m.e.tiffany@ larc.nasa.gov Abstract System for NCSTRL+ Michael L. Nelson NASA Langley Research Center MS 158 Hampton, VA 23681 m.l.nelson@ larc.nasa.gov The purpose of this paper is to describe the new subject classification system for the NCSTRL+ project. NCSTRL+ is a canonical digital library (DL) based on the Networked Computer Science Technical Report Library (NCSTRL). The current NCSTRL+ classification system uses the NASA Scientific and Technical (STI) subject classifications, which has a bias towards the aerospace, aeronautics, and engineering disciplines. Examination of other scientific systems showed similar discipline-centric and technical information classification weaknesses. Traditional, library-oriented classification systems represented all disciplines, but were too generalized to serve the needs of an STI oriented digital library. Lack of a suitable existing classification system led to the creation of a lightweight, balanced, general classification system that allows the mapping of more specialized classification schemes into the new framework. We have developed the following classification disciplines, while being compact and lightweight. 1 Introduction system to give equal weight to all STI Digital libraries (DLs) are quickly gaining acceptance and use in the scientific and research communities. NCSTRL+ is a canonical digital library based on the Networked Computer Science Technical Report Library (NCSTRL). The aim of NCSTRL+ is to provide users with a unified interface for multi-disciplinary/multi-genre searching [13]. One of the problems NCSTRL+ seeks to address is how to facilitate searching for information across diverse collections of specialized scientific and technical information. The two main stumbling blocks for users wishing to search for scientific and technical information are the lack of uniformity among on discipline-specific jargon. individual DLs and the reliance of the DLs The answer is to create a new canonical classification system. It must be general enough allow more specialized subject categories to be mapped into it, since the purpose is to incorporate specialized classification systems, not replace them. The new system must also be balanced to represent all disciplines equally and avoid over-specialization.

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Finally, the new systemmustalsobe lightweight,or it will be too cumbersometo work with efficiently. 2 Background The NCSTRL+ prototype utilized the NASA Scientific and Technical Information (STI) categories [12] (Appendix B). They were chosen because the subjects were already familiar to most users [13], and the structure was desired (Table 1). Main Subject Category Aeronautics Astronautics Chemistry and Materials Engineering Geosciences Life Sciences Mathematical and Computer Sciences Physics Social Sciences Space Sciences of the system was relatively close to what Subject Code 01 12 23 31 42 51 59 70 80 88 Table 1. NASA Scientific and Technical Information Topics The main problem with the NASA STI classification system is that it has a rather noticeable bias towards aeronautics, astronautics, and engineering topics to the detriment of other subjects. For example, there are 67 main and subcategories under engineering, but only 20 for mathematics and science combined. Social sciences and life sciences exhibit a similar lack of depth in their respective categories. In order to ensure equal representation within each subject category, it would be necessary to redistribute the number of subcategories allocated to each main subject. It would also be desirable to separate mathematics and computer science into separate categories. 3 Existing Specialized Classification Systems It would be easiest to replace the NASA STI system with a preexisting scientific or technical classification system. Unfortunately, most scientific and technical classification systems suffer from the same problem as the NASA STI system: the tendency to catalog subjects within the discipline in minute detail, ignoring ancillary subjects or giving them only a cursory categorization. There is a tendency to catalog what you know extremely well, while ignoring the categories that do not directly affect your profession. A summary of the specialized classification systems considered and why

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they were ultimately rejectedfor NSTRL+ can be seenin Table 2. Figure 1 showsa relative placementof both specializedandgeneralclassificationsystems,andhow none fall into the desiredrange. Examining thesediscipline-specificclassificationsystems underscoresthe fact that althoughthey do an excellentjob of creating classification structuresin their subjectspecialty,they lack the breadthof subjectmatterrequiredfor a generalpurposeclassificationsystem. Nameof Specialized Classification Scheme Center for AeroSpace Information (CASI) Defense and Technical Information Center (DTIC) Global Change Master Directory (GMCD) Physics E-print Archive American Mathematical Society (AMS) Reason Rejected Too large, bias towards aerospace Heavy emphasis on defense technology Earth science specific categories Categories are not well-balanced Too many categories Association for Computer Machinery (ACM) Categories too discipline-specific American Institute of Physics (AIP) Table 2. Specialized Classification O AIP O 0 AMS Increasing 0 DTIC complexity 0 GCMD O ACM Too complex Schemes Considered for NCSTRL+ O CASI LCC < Desired Range 0 Physics e-Print O Dewey Decimal Increasing generality Figure 1. Complexity vs. generality in classification systems considered for NCSTRL+.

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3.1 Center for AeroSpace Information (CASI) The Center for AeroSpace Information (CASI) catalogs bibliographic citations for Scientific and Technical Aerospace Reports (STARs). CASI has subject categories and major subject terms [4]. The problem with the subject category is that there are 76 subject categories to choose from--far too many for the NCSRL+ project. In addition, CASI takes its major subject terms from the NASA Thesaurus [11], which again, reflects a NASA bias towards aerospace, aeronautics, and engineering. Another level of classification is added by allowing multiple terms to be entered into the secondary subject field, again, from the NASA Thesaurus. Thesaurus terms are arranged in a hierarchy that is too detailed and complex to easily incorporate into NCSTRL+. 3.2 Defense and Technical Information Center (DTIC) The Defense Technical Information Center (DTIC) subject categories are also overly specialized, this time in subjects of special interest to the Department of Defense. DTIC has 25 main subject categories and 251 subcategories, with a military emphasis [6]. The main categories are numbered, with subcategories also numerically differentiated. It classifies to three levels deep. For example, the Astronomy and Astrophysics category only has three subheadings (Table 3), while the Guided Missile Technology subject category has nine distinct subcategories (Table 4). Due to its heavy emphasis on defense technology and issues, the DTIC classification system was not considered an appropriate candidate to replace the NASA STI subject categories. 03--Astronomy and Astrophysics 01 Astronomy 02 Astrophysics 03 Celestial Mechanics Table 3. DTIC Astronomy and Astrophysics subcategories 16--Guided Missile Technology 01 Guided Missile Launching and Basing Support 02 Guided Missile Trajectories, Accuracy and Ballistics 02/01 Guided Missile Dynamics, Configurations and Control Surfaces 03 Guided Missile Warheads and Fuzes 04 Guided Missiles 04/01 Air- and Space-Launched Guided Missiles 04/02 Surface-Launched Guided Missiles 04/03 Underwater-Launched Guided Missiles 05 Guided Missile Reentry Vehicles Table 4. DTIC Guided Missile Technology Subcategories

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3.3 Global Change Master Directory The Global Change Master Directory (GCMD) allows users to search by subject for Earth Science data. It has 11 main categories, all relating to specific areas of expertise in the Earth Sciences [8]. The GCMD catalogs data three levels deep, which allows for very specific searches (for example: Cryosphere: Sea Ice: Ice Types). However, GCMD is too limiting to be a general classification Science topics. 3.4 Physics E-print Archive The Physics E-print Archive stores system because it categorizes only Earth papers primarily written for the physics community, but also has papers on mathematics, nonlinear science, and computer science [15]. They have rudimentary subject classifications that seem to have arisen more out of necessity than intent. Most of the subcategories are under the main "Physics" category. High Energy Physics has 4 main categories Theory). Mathematics is one major category, (Experiment, Lattice, Phenomenology, and with individual disciplines in mathematics listed as subcategories. Simply put, the Physics E-print archive is not structured enough to be useful. The Physics E-print archive classification system does not provide a clear, balanced set of main and subcategories, nor does it list subjects unrelated to physics. This is understandable considering the targeted user group of this server and its evolutionary development. 3.5 American Mathematical Society The American Mathematical Society's geared specifically to classify mathematical (AMS) Mathematics Subject Classification [2] is papers and information. The Mathematics Subject Classification system has 95 main categories, ranging from "Algebraic Geometry" to "Abstract Harmonic Analysis". other disciplines among its main categories, While this categorization system does list it lists them only if they are in some way related to mathematics. In addition to being a large classification system, it is also quite involved. The instructions deem it "extremely helpful for both readers and classifiers to familiarize themselves with the entire classification system" [2]. A classification system that requires extensive familiarity to implement and search is not suitable for the purposes of NCSTRL+. 3.6 Association for Computer Machinery (ACM) The Association for Computer Machinery (ACM) Computing Classification System [3] uses the alphabetical letters A-K to denote main categories, separated by a period from numbers to denote subcategories (the exception to this rule is the "Miscellaneous" subcategory at the end of each main category. It is denoted by an "m"). Again, the emphasis on one particular discipline renders this classification system incomplete for NCSTRL+.

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3.7 American Institute of Physics (ALP) Probably the most complex classification system considered was that of the American Institute of Physics (ALP). It is called the Physics and Astronomy Classification System (PACS). Not only was PACS an enormous list (around 150 pages long), but it had a potentially confusing and complicated indexing scheme. According to the description, The PACS indexing categories are labeled by six-character Codes consisting of four numbers followed by a fifth character that can be either an uppercase letter or a plus or minus ... [the] sixth character is a lowercase character that serves as a check character [1]. PACS would be difficult to implement outside of a physics environment, due to the level of expertise required to catalog information in that scheme. It would also be extremely time consuming to map other classification codes onto PACS. Users unfamiliar with physics terminology would have difficulty finding the correct categories to search in. Last, but not least, it classifies only physics and astronomy categories. 4 Existing Generalized Classification Systems General classification systems were also considered for use in NCSTRL+. General classification schemes are specifically designed to classify a wide range of subjects in detail. The two most common general classification systems are the Library of Congress Classification System (LCC) and the Dewey Decimal System. It was found, however that the major shortcoming of a generalized classification system was its generality--too many subject categories were classified to make it useful for NCSTRL+ (Table 5). Name of Generalized Classification Scheme Library of Congress Classification Dewey Decimal System Reason Rejected Too complex, too detailed Too generalized Table 5. Generalized Classification Schemes considered for NCSTRL+. 4.1 Library of Congress Classification (LCC) The LCC system is well known to anyone who has visited an academic library. It consists of 21 main categories [10], with subcategories defined first by letters and then numbers. The LCC is a very large classification system intended for large collections. It

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provides enough breadth and depth to classify almost any collection. The fact that the LCC is such a large, complete classification system is precisely why it is unsuitable for use in NSCTRL+: it provides too much detail. Finding a copy of the LCC on the web is also a challenge, not to mention adapting it for use in a digital library environment, as the Pharos team discovered [14]. Aside from the implementation problems that LCC provides, properly mapping another DL's subject headers into the Library of Congress Classification system would take a fair amount of skill and time, negating the whole idea of adopting a simple, yet complete classification system. 4.2 Dewey Decimal System The Dewey Decimal System is used primarily by public libraries. It is, like the LCC, a general purpose classification system. It is much easier to use than the LCC, limiting itself to 10 major subjects, each with 10 secondary subjects [16]. Specificity is obtained by adding numbers after the decimal point. The 10 major areas are shown in Table 6. 000 Generalities 100 Philosophy and Psychology 200 Religion 300 Social Sciences 400 Languages 500 Science 600 Technology 700 Arts and Music 800 Literature 900 Geography and History Table 6. Dewey Decimal System Main Classifications The main advantage to the Dewey Decimal System is that is well known by most users. It is also reasonably compact, and easy to work with. The reason it was not chosen as the classifying system for NCSRL+ is that the subject headings are too general for a specialized library. While Dewey is appropriate for public libraries, it is simply not adequate for STI applications. Generalized library classifications schemes have the breadth of subject matter to be used by NCSTRL+, but lack the depth required by a scientific and technical library. They can also be bulky and difficult to implement in a digital library environment, and may require additional expertise to effectively catalog information and map other library classifications into them.

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5 Creating a New Canonical Classification System To create a new canonical classification major subject headings (similar to the Dewey per subject heading was chosen. system for NCSTRL+, a structure of 11 Decimal System [16] ) with 11 subclasses Once the number of main and subcategories was decided upon, the next phase was deciding what main/subcategories should be used. For the most part, the original NASA STI topics remained. The mathematics and computer science topic was divided into separate categories, and some subclasses were incorporated into newly created generalized subclasses or removed altogether. pruning, refer to the NASA STI Aeronautics To see an example of the reshuffling and subject classification (Table 7) and compare it to the NCSTRL+ Aeronautics subject classification (Table 8). In order to create the subcategory headers, sources that had previously been dismissed as too specialized to be used as a stand alone classification system were consulted to decide what constituted a "general" subcategory. For Chemistry and Materials, ChemDex Plus [5] was used. The Geosciences subject was renamed NASA's Earth Science Enterprise. To rework Earth Sciences, to make it consistent with the subclasses, the dictionary was used, as well as the author's experience working with Earth Science data. PACS [1] was useful in helping to solidify the subclasses for Physics and Space Sciences. PACS was a good detailed framework to check NCSTRL+'s general subclasses against (PACS categories were able to map to NCSTRL+ categories). The Computer Science category was developed with the help of the ACM Computing Classification System [3]. What was to be listed was already known, and the ACM classification system helped to identify were sub-subcategories. which items were subcategories and which Members of the NASA Langley Research Center's Technical Library staff with experience in cataloging reviewed the initial NCSTRL+ classification system. They suggested additions and clarifications, especially to the Aeronautics, Astronautics, Engineering, and Social Sciences categories. After the requisite changes were made, they gave their approval for its use as a classification system. The finished Canonical Classification System for NCSTRL+ can be seen in Appendix A.

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01 Aeronautics 02 Aerodynamics 02-01 AerodynamicsCharacteristics 02-02 Aerodynamicsof Bodies 03 Air TransportationandSafety 03-01 CommercialandGeneralAviation 03-02 HelicoptersandGroundEffect Machines 03-03 STOL/VTOL Aircraft 03-04 SupersonicTransport 03-05 Aircraft NoiseandSonicBoom 03-06 Aircraft SafetyandSafetyDevices 03-07 ClearAir Turbulence 04 Aircraft CommunicationsandNavigations O5 Aircraft Design,TestingandPerformance 05-01 HydraulicandPneumaticSystems 05-02 Auxiliary Electrical Systems 06 Aircraft Instrumentation 07 Aircraft PropulsionandPower 07-01 JetPropulsion O8 Aircraft Stability andControl 09 ResearchandSupportFacilities(Air) 09-01 Wind Tunnels Table 7. NASA STI Aeronautics main and subcategories 000 Aeronautics, General 000-010 History of Aeronautics 010 Aerodynamics 020 Commercial and General Aviation 030 Aviation Safety 040 Instrumentation 050 Communications 060 Propulsion and Power 070 Design 080 Aircraft Control 090 Research and Support Facilities Table 8. NCSTRL+ Aeronautics main and subcategories

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6 Related Projects Perhaps the most closely related project to the Canonical Classification System for NCSTRL+ is Pharos [14], an offshoot of the Alexandria Digital Library Project at University of California, Santa Barbara [7]. Pharos mapped newsgroups to the Library of Congress Classification subjects. It allowed users to type in keywords, and it returned the newsgroups that were most likely to contain the information the user was looking for. The Pharos authors detailed the difficulty they had in making LCC suitable for automated classification [7]. In particular, some of the cataloging conventions were redundant or inconsistent. Pharos was begun in 1997; however, it does not seem to have progressed past the demonstration stage. It is viable, but at present, it does not appear to be under further development. Larson [9] has also done research classification. After conducting experiments classification, he concluded "fully automatic with LCC categories and automated with differing methods of automatic classification may not be possible" using the LCC, but conceded that "semiautomatic classification...appears to be effective" [9]. This bolsters the contention that the LCC (in its present form) is simply too large and too complex to be used for automatic classification. The Scorpion research project used the Dewey Decimal System as the basis for its automatic classification system, and reported favorable results [17]. Dewey's class integrity (how well subject classifications are differentiated) and hierarchical structure were cited as the reasons for its success. The authors concluded "results indicate that Dewey is a very good knowledge base for automatic subject assignment tools" [17]. 7 Future Work Although the initial work of creating the main and subcategories for NCSTRL+ has been completed, work on the project continues. The current catalog of NCSTRL+ will need to be mapped to the new classification codes. As NCSTRL+ grows and incorporates the holdings of other DLs, those collections will also need to be mapped to the appropriate categories. It is possible that the current list may be incomplete or inadequate to handle certain specialized classification schemes. To test this new classification scheme, it will need to be implemented. Feedback from users should be encouraged, and the system will probably need to be adjusted to better serve the users. Another area that can be explored is whether or not an additional level of subcategorizing is useful (or necessary). It may turn out that two levels of classification are not enough. Again, only a real world test will give the necessary data to decide the relative merit of this classification system. 8 Conclusions Most scientific and technical classification schemes are too narrow in their focus to adequately fill the demands of NCSTRL+. They catalog within their areas of expertise in great detail, but only give cursory, if any, attention to fields outside of their specialties. In addition, the plethora of specialized, highly technical subclasses often found in 10

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scientific and technical classification systems that particular subject. can be confusing for a user unfamiliar with On the other hand, traditional library cataloging systems offer general classification subjects that are familiar to a majority of users. The drawback is that these systems were created to catalog large, diverse collections in minute detail. Not only is this level of classification not necessary, it is not wanted. Also, the general subject categories of traditional library cataloging NCSTRL+. Since existing classification systems to be used to catalog NCSTRL+, a canonical systems are not completely relevant to were either too complex or too generalized classification system was created to fill the need for a lightweight, general-purpose classification system. The goal is to provide a balanced classification system that will be familiar enough to allow novice users to find the information they are looking for, even if they lack specific keywords or terms. The new classification system presents a set number of subcategories. All disciplines a set number of main categories, each with relevant to the STI holdings are given equal weight in the listing. Specific topics can be placed appropriately under each subcategory. Existing, specialized categorization schemes can also be mapped at the subcategory level to allow users to search across diverse DLs. For viability, the NCSTRL+ classification system has been reviewed and approved Center's technical library cataloging staff. Acknowledgements by members of NASA Langley Research We would like to thank Nancy Kaplan, Garland Gouger, and John Ferrainolo of the NASA Langley Research Center Technical Library for their assistance in reviewing and contributing to this classification system. 11

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References . American Institute of Physics, "1998 Physics and Astronomy Classification System (PACS)." http ://www. aip. o rg/p ac s/p ac s. ht lril . American Mathematical Society, "Mathematics Subject Classification (1991)." http://www.arns.or_/msc 3. Association for Computing Machinery, (1998)." http:l/www.acm.org/classl19981overview.htnfl "ACM Computing Classification System . Center for Aerospace Information Technical Report Server, http://www, sti.nasa.gov/RECONselect.htrnl . ChemWeb ChemDex Plus, "Subject Headings." http://www.chemweb.com/databases/chemdex/chemdex.exe? action=brow se 6. Defense Technical Information Center, "Subject Category Coverage." http://www,dtic.mJlJdtic/subcaL_uide/#subcats[ . R. Dolin, D. Agrawal, A. E1 Abbadi, & J.Pearlman, "Using Automated Classification for Summarizing and Selecting Heterogeneous Information Sources," D-Lib Magazine, the Magazine for Digital Library Research, January, 1998. http://www.dlib.orJdlib/ianuary98/dolinJO 8. Global Change Master Directory, "Science http://gcmd.gsfc.nasa.gov/param search/top.html l dolin.html Keyword Interface." 9. R. R. Larson, "Experiments in Automatic Library of Congress Classification," Journal of the American Society for Information Science, 43 (2), 1992, pp. 130-148. 10. Library of Congress Classification System http://geography.miningco.com/library/congress/bllc.html 11. NASA Thesaurus http;//www, st i.nasa.gov/98Thesaurus/98thes.htm 12. NASA Scientific and Technical Information ftp://ftp, sti.na sa. gov/pub/scan/S CAN-TOPICS Program, "NASA STI Topics." 12

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13.M. L. Nelson, K. Maly, S. N. T. Shen, & M. Zubair, "NSTRL+: Adding Multi- Discipline and Multi-Genre Support to the Dienst Protocol Using Clusters and Buckets,"Proceedings of Advances in Digital Libraries 98, Santa Barbara, CA, April 22-24, 1998, pp. 128-136. 14. Pharos http://pharo s.alexandria.ucsb.edu 15. Physics E-print Archive, http://xxx.lanl.gov 16. Salt Lake Community College, "Dewey Decimal System." http://www, slcc.edu/lr/library/info/dewey.htm 17. R. Thompson, K. Sharer, D. Vizine-Goetz, "Evaluating Dewey Concepts as a Knowledge Base for Automatic Subject Assignment," Proceedings of ACM Digital Libraries '97, Philadelphia, PA, July 23-26, 1997, pp. 37-46. 13

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Appendix A A Canonical STI Classification System for NCSTRL+ Aeronautics 000 Aeronautics, General & History 010 Aerodynamics 020 Commercial and General Aviation 030 Aviation Safety 040 Instrumentation 050 Communications 060 Propulsion and Power 070 Design 080 Aircraft Control 090 Research and Support Facilities Astronautics 100 Astronautics, General & History 110 Astrodynamics 120 Space Vehicles and Space Stations 130 Safety 140 Instrumentation 150 Communications 160 Propulsion and Power 170 Design 180 Navigation and Guidance Systems 190 Research and Support Facilities Chemistry and Materials 200 Chemistry and Materials, General 210 Electrochemistry 220 Chemical Processes 230 Chemical Analysis 240 Organic Chemistry 250 Inorganic Chemistry 260 Physical Chemistry 270 Materials 270-010 Metallic 270-020 Non-metallic 270-030 Composite 280 Propellants and Fuels 290 Processing Engineering and Applied Technology 300 Engineering, General 310 Electrical Engineering 320 Communications 330 Electronics 340 Lasers and Masers 350 Fluid Mechanics and Heat Transfer 360 Mechanical Engineering 370 Instrumentation and Measurement 380 Structural Mechanics 14

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390 QualityAssurance 395 Photography EarthSciences 400 EarthSciences,General 410 Geophysics 410-010 Geology 410-020 Seismology 410-030 Geomagnetism 420 Oceanography 430 Geography 430-010 Cartograpy 440 EnergyProduction 440-010 EnergyResources 450 EnvironmentalIssues 450-010 Pollution 450-020 GlobalWarming 460 AtmosphericScience 460-010 Meteorology 460-020 Climatology 460-030 ClimatologicalPhenomena 460-030 UpperAtmosphere 460-040 Satellites 470 Hydrology Li_ Sciences 500 LifeSciences,General 510 Biology 520 Biochemistry 530 Medicine 530-010 AerospaceMedicine 530-020 ClinicalMedicine 530-030 PhysiologicalFactors 540 LifeSciencesTechnology 540-010 LifeSupportSystems 550 SpaceBiology 550-010 ExtraterrestrialLife 560 BiologicalPhysics 570 Pharmacology 580 Psychology 580-010 Cognition 590 Botany Mathematics 600 Mathematics,General 610 AppliedMathematics 620 TheoreticalMathematics 630 Statistics 640 NumericalAnalysis 650 Geometry 660 Topology 670 Probability 680 Logic 690 MathematicalPhysics 15

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ComputerScience 700 ComputerScience,General 710 ComputerNetworks 710-010 Internet 720 Hardware 730 Software 730-010 SoftwareEngineering 730-020 ProgrammingLanguages 740 InformationSystems 740-010 InformationManagement 740-020 Database 740-030 InformationRetrieval 750 Data 750-010 DataStorage 750-020 DataEncryption 750-030 DataStructures 760 ArtificalIntelligence 770 Robotics 780 ArtificialIntelligence 790 Human-ComputerInteraction Physics 800 Physics,General 805 ElementaryParticlesandFields 805-010 Relativity 805-020 UnifiedFieldTheoriesandModels 810 StatisticalPhysics 815 HighEnergyPhysics 820 Thermodynamics 825 QuantumPhysics 830 Solid-StatePysics 840 Gases,Plasmas,andElectricalDischarges 850 Optics 860 NuclearPhysics 870 AtomicandMolecularPhysics 880 CondensedMatter 890 Acoustics SocialSciences 900 SocialSciences,General 910 Law 920 PoliticalScience 925 GovernmentandMilitaryScience 930 Economics 940 Business 940-010 AdministrationandManagement 950 CommtmicationsandMedia 960 Transportation 970 TechnologyTransfer 970 Sociology 970-020 SocialPsychology 980 Education 985 LibraryandInformationScience 990 History 995 Biography 16

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SpaceSciences 1000 SpaceSciences 1010 Astronomy 1020 Astrophysics 1030 SolarSystem 1030-010 PlanetaryExploration 1040 TheMoon 1050 TheSun 1050-010 SolarAstronomy 1050-020 SolarPhysics 1060 Stars 1070 TheUniverse 1070-010 StellarSystems 1070-020 InterstellarMedium 1070-030 GalacticObjectsandSystems 1070-040 ExtragalacticObjectsandSystems 1070-050 SpaceRadiation 17

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Appendix B NASA STI SCAN Topics AERONAUTICS 01 AERONAUTICS (GENERAL) 02 AERODYNAMICS 02-01 AERODYNAMICS CHARACTERISTICS 02-02 AERODYNAMICS OF BODIES 02-03 AIRFOIL AND WING AERODYNAMICS 03 AIR TRANSPORTATION AND SAFETY 03-01 COMMERCIAL AND GENERAL AVIATION 03-02 HELICOPTERS AND GROUND EFFECT MACHINES 03-03 STOL/VTOL AIRCRAFT 03-04 SUPERSONIC TRANSPORT 03-05 AIRCRAFT NOISE AND SONIC BOOM 03-06 AIRCRAFT SAFETY AND SAFETY DEVICES 03-07 CLEAR AIR TURBULENCE 04 AIRCRAFT COMMUNICATIONS AND NAVIGATIONS 05 AIRCRAFT DESIGN, TESTING AND PERFORMANCE 05-01 HYDRAULIC AND PNEUMATIC SYSTEMS 05-02 AUXILIARY ELECTRICAL SYSTEMS 06 AIRCRAFT INSTRUMENTATION 07 AIRCRAFT PROPULSION AND POWER 07-01 JET PROPULSION 08 AIRCRAFT STABILITY AND CONTROL 09 RESEARCH AND SUPPORT FACILITIES (AIR) 09-01 WIND TUNNELS ASTRONAUTICS 12 ASTRONAUTICS (GENERAL) 13 ASTRODYNAMICS 13-01 CELESTIAL MECHANICS AND ORBITAL CALCULATIONS 14 GROUND SUPPORT SYSTEMS AND FACILITIES (SPACE) 14-01 SPACECRAFT GROUND SUPPORT 14-02 TEST FACILITIES 14-03 SIMULATORS AND SIMULATION 14-04 STERILIZATION 15 LAUNCH VEHICLES AND SPACE VEHICLES 15-01 LAUNCH VEHICLES 15-02 SOUNDING ROCKETS 15-03 SPACE PROBES 15-04 SCIENTIFIC SATELLITES 15-05 REENTRY VEHICLES 15-06 U.S.S.R SPACECRAFT 16 SPACE TRANSPORTATION 16-01 SPACE TRANSPORTATION AND MANNED SPACECRAFT 17 SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING 17-01 SPACE COMMUNICATIONS 17-02 NAVIGATION SYSTEMS 17-03 GUIDANCE SYSTEMS 17-04 TRACKING 18 SPACECRAFT DESIGN, TESTING AND PERFORMANCE 18

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18-01SPACECRAFTATTITUDECONTROLANDSTABILIZATION 18-02RENDEZVOUSANDDOCKING 18-03SPACESTATIONS 19SPACECRAFTINSTRUMENTATION 19-01SPACECRAFTANDAIRCRAFTINSTRUMENTATION 19-02SENSORSANDTRANSDUCERS 20SPACECRAFTPROPULSIONANDPOWER 20-01ROCKETENGINES,NOZZLESANDTHRUSTCHAMBERS 20-02AUXILIARYPROPULSION 20-03ELECTRICPROPULSION CHEMISTRYANDMATERIALS 23CHEMISTRYANDMATERIALS(GENERAL) 23-01CHEMICALANALYSIS 23-02CHEMICALPROCESSESANDENGINEERING 23-03LUMINESCENCE 23-04PHOTOCHEMISTRY 24COMPOSITEMATERIALS 24-01REINFORCEDMATERIALSANDFIBERS 24-02COMPOSITEMATERIALS 25INORGANICANDPHYSICALCHEMISTRY 25-01CORROSION 25-02METALCRYSTALS 25-03COATINGS 25-04ELECTROCHEMISTRY 26METALLICMATERIALS 26-01ALUMINUM 26-02BERYLLIUM 26-03LIQUIDMETALS 26-04STEEL 26-05TITANIUM 26-06REFRACTORYMETALS 26-07METALLURGY 27NONMETALLICMATERIALS 27-01PLASTICS 27-02ADHESIVES 27-03CERAMICS 27-04ELASTOMERS 27-05GRAPHITE 27-06POLYMERS 28PROPELLANTSANDFUELS 28-01LIQUIDPROPELLANTS 28-02SOLIDPROPELLANTS 29MATERIALSPROCESSING ENGINEERING 31ENGINEERING(GENERAL) 32COMMUNICATIONSANDRADAR 32-01COMMUNICATIONSATELLITES 32-02COMMUNICATIONEQUIPMENT 32-03COMMUNICATIONSYSTEMS 32-04TELEMETRY 32-05RADIONOISE 32-06COMMUNICATIONTHEORY 33ELECTRONICSANDELECTRICALENGINEERING 19

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33-01RADAREQUIPMENT 33-02SEMICONDUCTORSANDTRANSISTORS 33-03ANTENNAS 33-04ELECTRONICCOMPONENTS 33-05CIRCUITRY 33-06ELECTRICALEQUIPMENT 33-07AMPLIFIERS 33-08FEEDBACKANDCONTROLTHEORY 33-09ELECTROMAGNETICRADIATION 33-10MICROELECTRONICS 33-11MICROWAVEANDSUBMILLIMETERWAVETECHNOLOGY 33-12MAGNETISM 34FLUIDMECHANICSANDHEATTRANSFER 34-01BOUNDARYLAYERTECHNOLOGY 34-02GASDYNAMICS 34-03FLUIDICS 34-04FLUIDFLOW 34-05COMBUSTIONPHYSICS 34-06HEATTRANSFER,BASIC 34-07REENTRYHEATTRANSFER 34-08THERMALPROTECTION 34-09ABLATION 34-10CRYOGENICS 35INSTRUMENTATIONANDPHOTOGRAPHY 35-01PHOTOGRAPHY 35-02INFRAREDTECHNOLOGY 35-03INSTRUMENTSTANDARDSANDCALIBRATIONTECHNIQUES 35-04TEMPERATUREMEASUREMENT 35-05PRESSUREMEASUREMENT 35-06DISPLAYSYSTEMS 35-07DATARECORDING 35-08GASFLOWMEASUREMENT 36LASERSANDMASERS 36-01LASERSANDMASERS 36-02LASERAPPLICATIONS 37MECHANICALENGINEERING 37-01BEARINGSANDGEARS 37-02LUBRICATIONANDLUBRICANTS 37-03MACHINING 37-04FRICTIONANDWEAR 37-05SEALS 37-06WELDING 37-07METALFORMING 37-08PUMPS 37-09VACUUMTECHNOLOGY 37-10NONDESTRUCTIVETESTING 37-11TURBOMACHINERY 38QUALITYASSURANCEANDRELIABILITY 38-01QUALITYCONTROLANDRELIABILITY 39STRUCTURALMECHANICS 39-01SHELLS 39-02STRESSESANDLOADS 39-03STRUCTUREVIBRATIONANDDAMPING 39-04IMPACTPHENOMENA 39-05STRUCTURALFATIGUE 39-06SANDWICHCONSTRUCTION 20

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39-07STRESSANALYSIS 39-08STRUCTURALTESTSANDRELIABILITY GEOSCIENCES 42GEOSCIENCES(GENERAL) 43EARTHRESOURCESANDREMOTESENSING 43-01EARTHRESOURCES 43-02GEODESYANDCARTOGRAPHY 44ENERGYPRODUCTIONANDCONVERSION 44-01ENERGYRESOURCES 44-02FUELCELLSANDCHEMICALBATTERIES 44-03SOLARSPACEPOWER 44-04NUCLEARAUXILIARYPOWER 45ENVIRONMENTPOLLUTION 45-01ENVIRONMENTPOLLUTIONCONTROL 46GEOPHYSICS 46-01UPPEREARTHATMOSPHERE 46-02GEOLOGYANDSEISMOLOGY 46-03GEOMAGNETISM 47METEOROLOGYANDCLIMATOLOGY 47-01METEOROLOGICALSATELLITES 47-02WEATHERFORECASTING 47-03MICROMETEOROLOGY 47-04CLOUDRESEARCH 47-05METEOROLOGICALINSTRUMENTS 48OCEANOGRAPHY 48-01WATERRESOURCESANDOCEANOGRAPHY LIFESCIENCES 51LIFESCIENCES(GENERAL) 51-01BIOLOGY(GENERAL) 51-02BIOCHEMISTRY 52AEROSPACEMEDICINE 52-01AEROSPACEMEDICINE 52-02CLINICALMEDICINE 52-03PHYSIOLOGICALFACTORS 52-04BIOLOGICALRADIATIONEFFECTS 53BEHAVIORALSCIENCES 53-01PSYCHOLOGICALFACTORS 54MAN/SYSTEMSTECHNOLOGYANDLIFESUPPORT 54-01LIFESUPPORTSYSTEMS 54-02CREWSAFETYANDPROTECTIVECLOTHING 54-03HUMANENGINEERING 54-04MAN-MACHINESYSTEMS 54-05BIOINSTRUMENTATION 54-06ROBOTICS 55SPACEBIOLOGY 55-01EXTRATERRESTRIALLIFE MATHEMATICALANDCOMPUTERSCIENCES 59MATHEMATICALANDCOMPUTERSCIENCES(GENERAL) 59-01APPLIEDMATHEMATICS 59-02DATAPROCESSING 60COMPUTEROPERATIONSANDHARDWARE 60-01DIGITALANDANALOGCOMPUTERS 60-02AIRBORNEORSPACEBORNECOMPUTERS 21

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61COMPUTERPROGRAMMINGANDSOFTWARE 61-01COMPUTERSOFTWARE 61-02CAD/CAM 62COMPUTERSYSTEMS 63CYBERNETICS 63-01CYBERNETICSANDBIONICS 63-02ARTIFICIALINTELLIGENCE 64NUMERICALANALYSIS 64-01NUMERICALANALYSIS 65STATISTICSANDPROBABILITY 65-01PROBABILITYANDSTATISTICS 66SYSTEMSANALYSIS 67THEORETICALMATHEMATICS PHYSICS 70PHYSICS(GENERAL) 71ACOUSTICS 71-01ACOUSTICS 71-02ULTRASONICS 72ATOMICANDMOLECULARPHYSICS 72-01ATOMICPHYSICS 72-02MOLECULARPHYSICS 73NUCLEARANDHIGH-ENERGYPHYSICS 73-01NUCLEARPHYSICS 73-02RADIOACTIVITY 74OPTICS 74-01OPTICS 74-02LIGHT 75PLASMAPHYSICS 75-01PLASMAAPPLICATIONS 75-02PLASMADYNAMICS 75-03MAGNETOHYDRODYNAMICS 76SOLID-STATEPHYSICS 76-01SOLIDSTATEDEVICES 76-02SUPERCONDUCTIVITY 76-03DIELECTRICS 76-04EPITAXIALDEPOSITION 77THERMODYNAMICSANDSTATISTICALPHYSICS SOCIALSCIENCES 80SOCIALSCIENCES(GENERAL) 81ADMINISTRATIONANDMANAGEMENT 81-01AEROSPACEMANAGEMENT 82DOCUMENTATIONANDINFORMATIONSCIENCE 82-01INFORMATIONTECHNOLOGY 83ECONOMICSANDCOSTANALYSIS 84LAW,POLITICALSCIENCEANDSPACEPOLICY 84-01WORLDSPACEPROGRAMSANDAEROSPACELAW 84-02SPACECOMMERCIALIZATION 85URBAN TECHNOLOGY AND TRANSPORTATION 85-01 URBAN TECHNOLOGY AND TRANSPORTATION SPACE SCIENCES 88 SPACE SCIENCES (GENERAL) 22

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89ASTRONOMY 89-01SOLARASTRONOMY 89-02STELLARASTRONOMYANDCOSMOLOGY 89-03METEORSANDMETEORITES 90ASTROPHYSICS 90-01GRAVITATION 90-02ASTROPHYSICALPLASMAS 91LUNARANDPLANETARYEXPLORATION 91-01THEMOON 91-02PLANETARYSCIENCESANDEXPLORATION 92SOLARPHYSICS 93SPACERADIATION 93-01COSMICRADIATION 93-02SOLARRADIATIONANDACTIVITY 93-03RADIATIONBELTS 23

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REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson DavisHighway_Suite12_4_Ar_ingt_n_VA222_2-43_2_andt_the__ice_fManagementandBudget_Paperw_rkReducti_nPr_ject(_7_4-188) Washington, DC 20503. 1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED December 1998 Technical Memorandum 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Creating a Canonical Scientific and Technical Information Classification System for NCSTRL+ 6. AUTHOR(S) Melissa E. Tiffany Michael L. Nelson 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) NASA Langley Research Center Hampton, VA 23681-2199 8. PERFORMING ORGANIZATION REPORT NUMBER L-17797 ADDRESS(ES) IO. SPONSORING/MONITORING 9. SPONSORING/MONITORING AGENCY NAME(S) AND National Aeronautics and Space Administration Washington, DC 20546-0001 11. SUPPLEMENTARY NOTES 12a. DISTRIBUTION/AVAILABILITY STATEMENT Unclassified-Unlimited Subject Category 82 Distribution: Standard Availability: NASA CASI (301) 621-0390 13. ABSTRACT (Maximum 200 words) AGENCY REPORTNUMBER NASA/TM-1998-208955 12b. DISTRIBUTION CODE The purpose of this paper is to describe the new subject classification system for the NCSTRL+ project. NCSTRL+ is a canonical digital library (DL) based on the Networked Computer Science Technical Report Library (NCSTRL). The current NCSTRL+ classification system uses the NASA Scientific and Technical (STI) subject classifications, which has a bias towards the aerospace, aeronautics, and engineering disciplines. Examination of other scientific and technical information classification systems showed similar disciplinecentric weaknesses. Traditional, library-oriented classification systems represented all disciplines, but were too generalized to serve the needs of a scientific and technically oriented digital library. Lack of a suitable existing classification system led to the creation of a lightweight, balanced, general classification system that allows the mapping of more specialized classification schemes into the new framework. We have developed the following classification system to give equal weight to all STI disciplines, while being compact and lightweight 14. SUBJECT TERMS Digital Libraries, Subject Categories, Classification 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION OF REPORT OF THIS PAGE Unclassified Unclassified NSN 7540-01-280-5500 15. NUMBER OF PAGES 28 16. PRICE CODE AO3 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT OF ABSTRACT Unclassified Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. Z-39-18 298-102