Table Of ContentCitation-based Plagiarism Detection
Bela Gipp
Citation-based
Plagiarism Detection
Detecting Disguised
and Cross-language Plagiarism
using Citation Pattern Analysis
Bela Gipp
Berkeley, USA
Dissertation Otto-von-Guericke University Magdeburg, Germany, 2013
ISBN 978-3-658-06393-1 ISBN 978-3-658-06394-8 (eBook)
DOI 10.1007/978-3-658-06394-8
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Acknowledgements
This doctoral thesis would not have been possible without the collaboration
and generous support of numerous individuals and institutions. I am especially
grateful to my doctoral advisor, Professor Andreas Nürnberger, for his
dedication to my success in writing this thesis and supporting me in all my
research endeavors. I am thankful to Professor Claus Rautenstrauch for inspiring
me to pursue a PhD in the first place. Furthermore, I am indebted to the
professors Jim Pitman and Erik Wilde from the University of California,
Berkeley for inviting me to complete my research at UC Berkeley from 2009–
2013. Our open exchange of ideas and our collaboration on interesting projects
such as Mr. DLib, led to several joint publications.
I especially acknowledge my research group at SciPlore: Joeran Beel,
Corinna Breitinger, Mario Lipinski and Norman Meuschke, with whom it was a
pleasure to work over the years. The close collaboration and joint publications
with Norman while overseeing his master thesis, as well as during our
subsequent research, have significantly contributed to the development of the
CbPD approach. I also thank Joeran, Corinna and Mario for our joint projects
indirectly related to my doctoral research, such as the development of the open
source software, SciPlore Mindmapping, now known as Docear, the
development of the machine-readable digital library, Mr. DLib, and the research
on Co-citation Proximity Analysis. I wish to thank Christian Hentschel, Juliane
Stiller and my research colleagues as mentioned above, for their valuable
feedback and proofreading of the manuscript.
I wish to thank my past students at the OvGU Magdeburg, Wadi International
University and the UC Berkeley, as well as my most recent students at the HTW
Berlin, with whom I developed a web-based CbPD visualization prototype.
Working with students in lecture, and supervising bachelor and master projects is
a rewarding experience, which confirmed my desire to pursue a career in
academia. I also thank the participants of the CbPD user study for their time.
I gratefully acknowledge the organizations that provided my colleagues and me
with the funding to realize our research. I thank EXIST for a generous grant from
VI Acknowledgements
the German Federal Ministry of Economics and Technology. Moreover, I
thankfully acknowledge a NSF grant that allowed us to work on a related project,
Mr. DLib. I am indebted to the German Academic Exchange Service (DAAD)
for their scholarship that allowed me to research at UC Berkeley, as well as my
employer, the SAP-sponsored VLBA-lab at the OvGU. I also wish to thank the
Google Scholar team and Bill Schilit for their collaboration, and for inviting me
to present my citation-based approach to plagiarism detection at Google in
Mountain View. I thank ACM, SIGIR, ECDL and JCDL for their conference-
travel grants and I also gratefully acknowledge the State of Saxony-Anhalt for its
financial support of the patent applications.
Finally, and most importantly, I thank my loving family and my wonderful
girlfriend, for always supporting me in all my endeavors.
Contents
Acknowledgements .............................................................................................. V
Contents .............................................................................................................VII
List of Tables ...................................................................................................... XI
List of Figures .................................................................................................. XIII
Glossary .......................................................................................................... XVII
Abstract ......................................................................................................... XXIII
Kurzfassung ................................................................................................... XXV
1 Introduction ..................................................................................................... 1
1.1 Problem Setting ....................................................................................... 1
1.2 Motivation ............................................................................................... 3
1.3 Research Objective ................................................................................. 4
1.4 Thesis Outline ......................................................................................... 6
2 Plagiarism Detection ....................................................................................... 9
2.1 Academic Plagiarism .............................................................................. 9
2.1.1 Definition ................................................................................... 10
2.1.2 Forms of Academic Plagiarism .................................................. 11
2.1.3 Prevalence of Plagiarism in the Academic Environment ........... 13
2.2 Plagiarism Detection Approaches ......................................................... 17
2.2.1 Generic Detection Approach ..................................................... 17
2.2.2 Overview of Plagiarism Detection Approaches ......................... 19
2.2.3 Fingerprinting ............................................................................ 22
2.2.4 Term Occurrence Analysis ........................................................ 26
2.2.5 Stylometry ................................................................................. 30
2.2.6 Cross-Language Plagiarism Detection ....................................... 32
2.3 Plagiarism Detection Systems ............................................................... 33
2.3.1 Evaluations of PDS .................................................................... 34
2.3.2 Technical Weaknesses of PDS .................................................. 39
2.4 Conclusion ............................................................................................ 40
VIII Contents
3 Citation-based Document Similarity .............................................................. 43
3.1 Terminology .......................................................................................... 44
3.1.1 Citation vs. Reference ................................................................ 44
3.1.2 Similarity vs. Relatedness .......................................................... 45
3.1.3 Dimensions of Similarity: Lexical, Semantic, Structural ........... 45
3.2 Citation-based Similarity Measures ...................................................... 47
3.2.1 Direct Citation ............................................................................ 47
3.2.2 Bibliographic Coupling .............................................................. 48
3.2.3 Co-citation .................................................................................. 50
3.2.4 Amsler ........................................................................................ 52
3.2.5 Co-citation Proximity-based Methods ....................................... 52
3.3 Conclusion ............................................................................................. 54
4 Citation-based Plagiarism Detection .............................................................. 57
4.1 Concept ................................................................................................. 58
4.1.1 Citing Behavior .......................................................................... 62
4.2 Citation Characteristics Considered ...................................................... 64
4.2.1 Bibliographic Coupling Strength ............................................... 64
4.2.2 Probability of Citation Co-occurrence ....................................... 64
4.2.3 Order and Proximity of Citations ............................................... 65
4.3 Challenges to Citation Pattern Identification ......................................... 66
4.3.1 Unknown Pattern Constituents ................................................... 66
4.3.2 Transpositions ............................................................................ 67
4.3.3 Scaling ........................................................................................ 67
4.3.4 Insertions or Substitutions of Citations ...................................... 68
4.4 Design of Citation-based Detection Algorithms .................................... 68
4.4.1 Bibliographic Coupling (BC) ..................................................... 69
4.4.2 Longest Common Citation Sequence (LCCS) ........................... 70
4.4.3 Greedy Citation Tiling (GCT) .................................................... 70
4.4.4 Citation Chunking (Cit-Chunk) .................................................. 73
4.5 Projected Suitability of CbPD Algorithms for Plagiarism Forms ......... 80
4.6 Assessment of Identified Citation Patterns ............................................ 83
4.6.1 Citing Frequency-Score (CF-Score) ........................................... 83
4.6.2 Continuity-Score (Cont.-Score) ................................................. 85
Contents IX
4.7 Conclusion ............................................................................................ 87
5 Prototype: CitePlag ........................................................................................ 89
5.1 Document Parser ................................................................................... 90
5.2 Database ................................................................................................ 93
5.2.1 Consolidation of Reference Identifiers ...................................... 94
5.3 Detector ................................................................................................. 95
5.4 Frontend ................................................................................................ 96
5.5 Conclusion ............................................................................................ 99
6 Quantitative and Qualitative Evaluation ...................................................... 101
6.1 Methodology ....................................................................................... 102
6.1.1 Test Collection Requirements .................................................. 104
6.1.2 Test Collection Challenges ...................................................... 106
6.1.3 GuttenPlag Wiki ...................................................................... 108
6.1.4 VroniPlag Wiki ........................................................................ 109
6.1.5 PubMed Central OAS .............................................................. 111
6.1.6 Summary and Comparison of Test Collections ....................... 113
6.2 Evaluation using GuttenPlag Wiki ...................................................... 116
6.3 Evaluation using VroniPlag Wiki ....................................................... 121
6.3.1 Evaluation: Random Sample of Sources .................................. 121
6.3.2 Evaluation: Translated Plagiarism ........................................... 126
6.3.3 Evaluation: Plagiarism Case Heun ........................................... 129
6.3.4 Conclusion VroniPlag Wiki ..................................................... 135
6.4 Evaluation using PubMed Central OAS.............................................. 136
6.4.1 Methodology ............................................................................ 139
6.4.2 Results ..................................................................................... 157
6.4.3 Conclusion of PMC OAS Evaluation ...................................... 195
6.5 Conclusion of Evaluations .................................................................. 198
7 Summary & Future Work ............................................................................ 203
7.1 Summary ............................................................................................. 203
7.2 Contributions ...................................................................................... 207
7.3 Future Work ........................................................................................ 211
7.3.1 General Research Need ............................................................ 212
X Contents
7.3.2 Improvements to Detection Accuracy ...................................... 213
7.3.3 Additional Applications ........................................................... 215
7.3.4 Further Evaluations .................................................................. 219
References ......................................................................................................... 223
Appendix ........................................................................................................... 265
A Preliminary PMC OAS Corpus Analysis ..................................................... 266
A.1 Bibliographic Coupling ....................................................................... 266
A.2 Longest Common Citation Sequence .................................................. 273
A.3 Greedy Citation Tiling ......................................................................... 278
A.4 Citation Chunking ............................................................................... 286
A.5 Character-based PDS Sherlock ............................................................ 293
A.6 Character-based PDS Encoplot ........................................................... 294
B Technical Details of the CitePlag Prototype ................................................ 296
B.1 Sentence-Word-Tagger (SW-Tagger) ................................................. 296
B.2 Data Parser .......................................................................................... 300
B.3 Consolidation of Reference Identifiers ................................................ 302
B.4 Database Documentation ..................................................................... 304
C Data and Source-code Downloads ............................................................... 311
D Related Publications .................................................................................... 313
E Patent Application ....................................................................................... 318
F User Study Feedback ................................................................................... 329
G Reactions of Contacted Authors .................................................................. 331
H Empirical Studies on Plagiarism Frequencies .............................................. 336
I Studies on Citation-based Similarity Measures ........................................... 339
J Overview of Selected PDS .......................................................................... 343
Index .................................................................................................................. 347
