Jointly published by Akadémiai Kiadó, Budapest
and Kluwer Academic Publishers, Dordrecht
Scientometrics,
Vol. 56, No. 3 (2003) 357–367
A new classification scheme of science fields and subfields
designed for scientometric evaluation purposes
WOLFGANG GLÄNZEL,*,** ANDRÁS SCHUBERT**
*Katholieke Universiteit Leuven, Steunpunt O&O Statistieken, Leuven (Belgium)
**Hungarian Academy of Sciences, Institute for Research Organisation, Budapest (Hungary)
A two-level hierarchic system of fields and subfields of the sciences, social sciences and arts &
humanities is proposed. The system was specifically designed for scientometric (evaluation)
purposes with the ultimate goal of classifying every single document into a well-defined category.
This goal was achieved using a three-step iterative process. The basic concepts and some
preliminary results are presented.
Introduction
Classification of science into a disciplinary structure is at least as old as science
itself. After many centuries of constructive but yet inconclusive search for a perfect
classification scheme, the only sensible approach to the question appears to be the
pragmatic one: what is the optimal scheme for a given practical purpose? To this end,
ever so many systems have been conceived and installed by general and special
libraries, publishers, encyclopedias and, in ever growing number, by electronic
databases, internet based information services, web crawlers, etc. Classification systems
developed by the producer of the Science Citation Index (SCI; ISI – Thomson
Scientific, PA, USA), by institutions working extensively with this database and by the
producers of other multidisciplinary science journal databases are worthy of
distinguished attention (see, for instance, Narin, 1976). These classification systems are
mostly based on journal assignment, originally created for retrieval purposes. Most
existing systems, however, proved to have shortcomings when used in the context of
research evaluation. The classification of scientific literature into appropriate subject
fields is, nevertheless, one of the basic preconditions of valid scientometric analyses.
Publication activity and citation habits considerably differ among subfields. In
comparative studies, inappropriate reference standards obtained from questionable
subject assignment might result in misleading conclusions. This paper is, therefore,
Received October 11, 2002.
Address for correspondence:
WOLFGANG GLÄNZEL
Katholieke Universiteit Leuven
Steunpunt O&O Statistieken, Dekenstraat 2, B-3000 Leuven, Belgium
E-mail: h1533bra@ella.hu
0138–9130/2003/US $ 20.00
Copyright © 2003 Akadémiai Kiadó, Budapest
All rights reserved
W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
aiming at the development of a new classification system including also papers published in
multidisciplinary journals, and especially designed for research evaluation purposes.
Methods
For the given practical purpose, two different basic schemes are used: hierarchic and
fine-structured classification systems used in information retrieval and more “robust”
schemes emphasizing science organisation aspects and science policy needs.
In this paper, a two-level hierarchical classification scheme has been constructed, so
that the categories cover the whole scope of the sciences by and large evenly, and the
subfields behave consistently in scientometric evaluations, i.e., common standards
could be set in each of them regarding publication and citation habits.
The objectives of the work have been approached by three successive steps allowing
multiple feedback loops throughout the whole process.
1. The “cognitive” approach (setting the categories):
In this iterative process, an initial scheme has been elaborated on the basis of both
the experience of scientometricians and external experts.
2. The “pragmatic” approach (journal classification):
On the basis of existing journal classification schemes the majority of the journal
set extracted from the SCI has been classified into the preset subfields. The
classification scheme has been adjusted according to co-heading frequency to keep
multiple assignments within reasonable limits.
3. The “scientometric” approach (article classification):
Articles published in core journals can be unambiguously classified into the
subfield of the given journals. Articles of un-assignable or ambiguously assignable
journals are classified individually using the analysis of references. The results of
this classification exercise had a retroactive effect on the journal classification and
also on the basic fields/subfield structure.
Results
Step 1 – The “cognitive” approach (setting the categories)
The application of the above methods resulted in a system with 12 first-level
categories (fields) and 60 second-level categories (subfields) of the sciences. For the
social sciences and the humanities 3 major fields and 7 subfields were obtained. The
results are presented in Table 1.
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W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
Table 1. Fields and subfields of sciences, social sciences and arts & humanities
1.
AGRICULTURE & ENVIRONMENT
A1 Agricultural Science & Technology
A2 Plant & Soil Science & Technology
A3 Environmental Science & Technology
A4 Food & Animal Science & Technology
2.
BIOLOGY (ORGANISMIC & SUPRAORGANISMIC LEVEL)
Z1 Animal Sciences
Z2 Aquatic Sciences
Z3 Microbiology
Z4 Plant Sciences
Z5 Pure & Applied Ecology
Z6 Veterinary Sciences
3.
BIOSCIENCES (GENERAL, CELLULAR & SUBCELLULAR BIOLOGY; GENETICS)
B0 Multidisciplinary Biology
B1 Biochemistry/Biophysics/Molecular Biology
B2 Cell Biology
B3 Genetics & Developmental Biology
4.
BIOMEDICAL RESEARCH
R1 Anatomy & Pathology
R2 Biomaterials & Bioengineering
R3 Experimental/Laboratory Medicine
R4 Pharmacology & Toxicology
R5 Physiology
5.
CLINICAL AND EXPERIMENTAL MEDICINE I (GENERAL & INTERNAL MEDICINE)
I1 Cardiovascular & Respiratory Medicine
I2 Endocrinology & Metabolism
I3 General & Internal Medicine
I4 Hematology & Oncology
I5 Immunology
6.
CLINICAL AND EXPERIMENTAL MEDICINE II (NON-INTERNAL MEDICINE SPECIALTIES)
M1 Age & Gender Related Medicine
M2 Dentistry
M3 Dermatology/Urogenital System
M4 Ophthalmology/Otolaryngology
M5 Paramedicine
M6 Psychiatry & Neurology
M7 Radiology & Nuclear Medicine
M8 Rheumatology/Orthopedics
M9 Surgery
7.
NEUROSCIENCE & BEHAVIOR
N1 Neurosciences & Psychopharmacology
N2 Psychology & Behavioral Sciences
Scientometrics 56 (2003)
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W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
Table 1. (cont.)
8.
CHEMISTRY
C0 Multidisciplinary Chemistry
C1 Analytical, Inorganic & Nuclear Chemistry
C2 Applied Chemistry & Chemical Engineering
C3 Organic & Medicinal Chemistry
C4 Physical Chemistry
C5 Polymer Science
C6 Materials Science
9.
PHYSICS
P0 Multidisciplinary Physics
P1 Applied Physics
P2 Atomic, Molecular & Chemical Physics
P3 Classical Physics
P4 Mathematical & Theoretical Physics
P5 Particle & Nuclear Physics
P6 Physics of Solids, Fluids And Plasmas
10. GEOSCIENCES & SPACE SCIENCES
G1 Astronomy & Astrophysics
G2 Geosciences & Technology
G3 Hydrology/Oceanography
G4 Meteorology/Atmospheric & Aerospace Science & Technology
G5 Mineralogy & Petrology
11. ENGINEERING
E1 Computer Science/Information Technology
E2 Electrical & Electronic Engineering
E3 Energy & Fuels
E4 General & Traditional Engineering
12. MATHEMATICS
H1 Applied Mathematics
H2 Pure Mathematics
13. SOCIAL SCIENCES I (GENERAL, REGIONAL & COMMUNITY ISSUES)
S1 Education & Information
S2 General, Regional & Community Issues
14. SOCIAL SCIENCES II (ECONOMICAL & POLITICAL ISSUES)
O1 Economics, Business & Management
O2 History, Politics & Law
15. ARTS & HUMANITIES
U1 Arts & Literature
U2 Language & Culture
U3 Philosophy & Religion
An interesting side effect of this new category system is that part of the life-science
related fields covered by the SSCI such as parts of Psychology & Behavior and
Paramedicine are integrated into the corresponding science areas (see subfields N2 and
M5, respectively).
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W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
Step 2 – The “pragmatic” approach (journal classification)
The majority of the journal set extracted from the SCI could be classified on the
basis of existing journal classification schemes into the preset subfields presented in
Table 1. The scheme had to be adjusted according to co-heading frequency to keep
multiple assignments within reasonable limits. Examples for journal assignment
obtained this way are given in Table 2.
Table 2. Example for journal classification based on the ‘pragmatic’ approach
Journal title
Natural Product Reports
Natural Resources Journal
Natural Toxins
Nature*
Nature & Resources
Nature Biotechnology
Nature Cell Biology
Journal of the American Chemical Society*
Journal of the American Leather Chemists Association
Journal of the American Musicological Society
Schweizer Archiv für Tierheilkunde
Schweizerische Mineralogische und Petrographische Mitteilungen
Schweizerisches Archiv für Volkskunde
Science*
Vol. year
2000
2000
1999
2001
2000
1999
2001
2001
1996
2000
1998
2000
2001
2001
F1
B1
A3
R4
X0
A3
Z3
B1
C0
C2
U1
Z6
G2
S2
X0
F2
F3
F4
C3
O2
B2
C6
G5
*
These journals are subject to the ‘scientometric’ approach in step 3
The journals assigned to category ‘X0’, i.e., to multidisciplinary sciences, were
subjected to further treatment according to the ‘scientometric approach’ as described in
step 3. In particular, the papers published in the journals Nature and Science (see
Table 2) were individually assigned to both subfields and major fields. Similarly, papers
published in JACS will be individually assigned to second-level categories, whereas
they were automatically assigned to the first-level field Chemistry through the journal
assignment ‘C0’ (see Table 2).
Scientometrics 56 (2003)
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W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
Figure 1. Percentage shares of fields in the total (1998)
Figure 1 gives a first impression on the distribution of publications and citations
over fields. For this sample, all papers indexed in the 1998 volume of the CD-Edition of
the SCI as Articles, Letters, Notes and Reviews have been taken into consideration.
Citations have been counted for a three-year citation window beginning with the
publication year, that is, for the 1998-2000 period. The distribution by fields is more
balanced than it was in the case of the schemes comprising five and eight fields,
respectively, previously used at ISSRU, Budapest. Nevertheless, Chemistry is the
largest field in terms of publication output, followed by Physics and the the two clinical
and experimental medicine fields. The smallest ones are Mathematics, Neuroscience &
Behavior and Geosciences & Space Sciences. From the viewpoint of citations, the field
Biosciences (General, Cellular & Subcellular Biology; Genetics) receives the lion’s
share, followed by two Clinical and Experimental Medicine fields and the natural
science fields, Chemistry and Physics. This is in part a conseques of the known fieldbiasses in scientific communication.
A breakdown by second-level categories has been made to visualise the distribution
of publication output and citation impact over subfields within major fields. Table 3
gives an insight into the weight and influence the individual subfields have on the field
total. The disciplinary citation impact ranges between 0.68 for H2 (Pure Mathematics)
to 10.14 for B2 (Cell Biology).
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W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
Table 3. Percentage shares of subfields in the main fields and their citation impact
(Publications: 1998, Citation window: 1998-2000)
FIELD
Agriculture & Environment
Biology
Biosciences
Biomedical Research
Clinical and Experimental Medicine I
Clinical and Experimental Medicine II
Neuroscience & Behavior
Chemistry
Scientometrics 56 (2003)
Subfield
A1
A2
A3
A4
Z1
Z2
Z3
Z4
Z5
Z6
B0
B1
B2
B3
R1
R2
R3
R4
R5
I1
I2
I3
I4
I5
M1
M2
M3
M4
M5
M6
M7
M8
M9
N1
N2
C0
C1
C2
C3
C4
C5
C6
Share of subfield in the field total
Publiactions
Citations
8.6%
23.6%
38.3%
34.9%
15.7%
10.3%
41.0%
18.4%
10.2%
11.0%
7.4%
66.9%
21.1%
24.3%
15.3%
7.2%
16.5%
47.5%
17.3%
20.4%
11.1%
27.3%
25.4%
20.3%
14.9%
4.4%
11.2%
7.6%
24.9%
15.1%
9.4%
4.3%
19.3%
87.3%
21.5%
14.3%
21.9%
11.7%
15.4%
22.3%
6.6%
23.6%
7.4%
18.6%
46.5%
33.2%
9.7%
6.7%
57.1%
17.2%
9.2%
4.9%
3.7%
72.3%
32.0%
23.5%
13.6%
4.0%
29.5%
41.2%
14.5%
17.7%
11.9%
20.0%
31.8%
25.7%
11.7%
2.5%
11.0%
5.5%
28.9%
20.2%
9.0%
3.7%
15.3%
93.8%
11.1%
21.8%
23.8%
6.8%
20.8%
21.7%
6.6%
14.0%
Subfield
Impact
1.55
1.42
2.20
1.72
1.96
2.07
4.42
2.97
2.85
1.40
3.34
7.23
10.14
6.47
3.17
1.97
6.39
3.10
2.99
3.98
4.89
3.36
5.73
5.81
2.03
1.49
2.52
1.88
3.00
3.45
2.45
2.21
2.04
5.58
2.67
4.06
2.88
1.54
3.59
2.58
2.64
1.58
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W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
Table 3. (cont.)
FIELD
Physics
Geosciences & Space Sciences
Engineering
Mathematics
Subfield
P0
P1
P2
P3
P4
P5
P6
G1
G2
G3
G4
G5
E1
E2
E3
E4
H1
H2
Share of subfield in the field total
Publiactions
Citations
17.5%
29.0%
10.9%
17.2%
6.2%
9.9%
28.3%
33.8%
50.4%
16.3%
25.2%
9.2%
26.6%
42.8%
22.6%
22.8%
68.1%
48.8%
22.8%
22.5%
14.5%
12.1%
5.7%
12.1%
24.3%
54.0%
41.1%
17.5%
23.0%
3.5%
25.8%
49.2%
21.4%
16.9%
74.0%
35.0%
Subfield
Impact
3.70
2.20
3.79
2.00
2.58
3.50
2.44
5.16
2.63
3.46
2.94
1.23
1.11
1.31
1.08
0.84
1.03
0.68
Step 3 – The “scientometric” approach (article classification)
All papers published in journals not assignable to ‘well-defined’ subject categories
have to be assigned individually, i. e., paper by paper. Two levels can be distinguished,
first the Multidisciplinary Science journals like Nature, Science, PNAS US and, second,
the general journals not specialised to any particular subject within one broader field,
for instance, the chemistry journals Journal of the American Chemical Society (JACS)
and Angewandte Chemie – International Edition. Among the possible approaches to
solve this problem, we just mention the method of delimiting subfields on the basis of
the analysis of cognitive words from the address field proposed by de Bruin and Moed
(1993) and the method of analysing the reference literature proposed by Glänzel et al.
(1999a, b). The ‘scientometric approach’ applied here is based on the methodology of
reference analysis according to Glänzel et al. (1999a, b). Tables 4 and 5 presents
examples for identified papers published in Nature and Science. As already mentioned
in the paper by Glänzel et al. (1999a), a considerable number of papers (mainly papers
without specific references and without institutional addresses) published in the two
multidisciplinary journals Nature and Science could be considered scientific journalism
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Scientometrics 56 (2003)
W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
rather than original reports on scientific research. Nevertheless, ISI usually regards
these papers as scientific articles. Such papers might practically be excluded from
scientometric analyses.
Table 4. Example for identified papers published in Nature (2000, Vol. 408)
(Fi (i = 1, 2, 3, 4) – subject codes with rank i by frequency, % –frequency in per cent)
F1
%
F2
%
F3
%
F4
%
SCI
Refs.
1st author
1st page
Title
P3 36.4 P4 27.3 P6 27.3
–
[small]
11
Zhang J
835
Flexible filaments in a
flowing soap film as a
model for onedimensional flag in a
two-dimensional wind
Z2 57.9 Z4 21.1 Z5 15.8
–
[small]
19
Salih A
850
Fluorescent pigments
in corals are
photoprotective
19.0
21
Stuphorn V
857
Performance
monitoring by the
supplementary eye
field
N1 61.9 N2 23.8 M6 19.0 M7
Table 5. Example for identified papers published in Science (2001, Vol. 294)
(Fi (i = 1, 2, 3, 4) – subject codes with rank i by frequency, % – frequency in per cent)
F1
F2
%
F3
%
1st author
1st page
F4
%
SCI
Refs.
15.4 Z3 15.4 B0 15.4
–
–
13
d’Aignaux JN
1729
Predictability of the
UK variant
Creutzfeldt-Jacob
disease epidemic
P0 33.3 P6 25.0 P1 16.7
–
–
12
Matsuda T
2136
Oscillating rows of
vortices in
superconductors
30.8
26
Smith DE
2141
Seasonal variations of
snow depth on Mars
I3
%
G1 53.8 G2 53.8 G3 30.8 G4
Title
The following examples are concerned with the individual assignement of papers
published in ‘general’ chemistry journals in 1993. In particular, the American journal
JACS and the German journal Angewandte Chemie – International Edition have been
chosen. Figures 2 and 3 show the results. Although the two journals have had similar
profiles in 1993, there are some differences that should be discussed. The largest share
Scientometrics 56 (2003)
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W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
of both journals (30% and 36%, respectively) is devoted to Organic & Medicinal
Chemistry (C3). The assignment of a relatively great share of papers to
Multidisciplinary Chemistry (C0) is due to journal self-citations. About 14% of the
papers published in JACS in the year under study is devoted to the subfield of
Biochemistry/Biophysics/Molecular Biology (B1), whereas about the same share of
papers published in Angewandte Chemie could be assigned to Analytical, Inorganic &
Nuclear Chemistry (C1).
Figure 2. Example for identified papers published in JACS (1993)
Figure 3. Example for identified papers published in Angewandte Chemie – International Edition (1993)
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Scientometrics 56 (2003)
W. GLÄNZEL, A. SCHUBERT: A new classification scheme of science fields
The assignment of papers in both journals to Physics shows that publications can
well be assigned to other fields although the journal is a typical chemistry journal. This
illustrates that research has become increasingly interdisciplinary.
The share of unidentified papers amounts to 6.4% (JACS) and 13.9% (Angewandte
Chemie). For these papers, the assignment to the category Multidisciplinary Chemistry
(C0) seems to be justified. However, the two examples show that the majority of the
papers can be individually assigned to ‘well-defined’ second-level categories.
Conclusions
Beyond the standard use of the classification scheme like the determination of
publication profiles for institutions or countries, or the calculation of reference
standards for relative citation indicators the profiling of authors and research groups is a
further important application. Given the results of article classification, the disciplinary
affiliation of their authors can be determined, either individually or by group. The
authors’ activity is often not limited to a single subfield, it usually covers a range of
subfields with varying weights and their field/subfield profile can be constructed. Such
profiles are of primary importance in scientometric evaluation, since standards of
scientometric indicators can be set only within subfields, therefore it is only the activity
profile that can be accompanied by matching profiles of indicators like, e.g., impact
measures, citation rates or reference age.
References
DE BRUIN, R. E., H. F. MOED, Delimitation of scientific subfields using cognitive words from corporate
addresses in scientific publications, Scientometrics, 26 (1993) 65–80.
GLÄNZEL, W., A. SCHUBERT, H. J. CZERWON, An item-by-item subject classification of papers published in
multidisciplinary and general journals using reference analysis, Scientometrics, 44 (1999) 427–439.
GLÄNZEL, W., A. SCHUBERT, U. SCHOEPFLIN, H. J. CZERWON, An item-by-item subject classification of
papers published in journals covered by the SSCI database using reference analysis, Scientometrics, 46
(1999) 431–441.
NARIN, F., Evaluative Scientometrics: The Use of Publication and Citation Analysis in the Evaluation of
Scientific Activity, Computer Horizons, Inc., Washington, D.C., 1976.
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