Mono- and Cross-Lingual Paraphrased Text Reuse and Extrinsic Plagiarism Detection Muhammad Sharjeel School of Computing and Communications, Lancaster University Supervisors: Dr. Paul Rayson Dr. Rao Muhammad Adeel Nawab Lancaster University, COMSATS University Islamabad, Lancaster, United Kingdom Lahore Campus, Pakistan [email protected] [email protected] A dissertation submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in Computer Science June 23, 2020 This thesis is dedicated to my mother, and my late father. Acknowledgements In the Name of Allah, the Most Gracious, the Most Merciful First and foremost, I thank the Almighty Allah (SWT), the ultimate source of all knowledge and wisdom in this world, for His countless blessings on me. Regarding my dissertation, I would like to express my sincere gratitude towards my thesis supervisors, Dr. Paul Rayson and Dr. Rao Muhammad Adeel Nawab. And I wish to “reuse” this sentence in so many ways, to show how grateful I am for their guidance, continuous motivation, and outstanding support that formed an endless “corpus” of wisdom that will be with me, always! I greatly admire Dr. Paul Rayson for being a kind, accessible, and an amiable supervisor. I am indebted to Dr. Rao Muhammad Adeel Nawab for mentoring my research for the past several years and helping me to develop a strong background in Natural Language Processing and Machine Learning. A thanks also goes to all the anonymous reviewers for their invaluable feedback that has led to significant improvements in my PhD study. A heartfelt thanks goes to my parents! Words cannot express my feelings, espe- cially towards my mother. I am obliged to her for the countless prayers and efforts for me. After the death of my father, she has played a vital role in my upbringing and the education I received in my early years and finally, achieving this milestone. I extend my thanks to my sister and two brothers for their endless support and encouragement. A special mention for my little niece Yashfa and nephew Munzir, though both of them provided enough distraction in this journey, it could never have been such a joyful ride without them. Finally, I wish to thank my loving and supportive wife, Dania, who has just come into my life and to our first child which we are expecting to arrive later in the year. I am fortunate to have the following people around me as colleagues and friends, Mr. Hafiz Rizwan Iqbal, Mr. Jawad Shafi Mian, Mr. Touseef Tahir, Mr. Shahbaz Akhtar Abid, Mr. Abdul Wahab, Mr. Muhammad Anas Masood, Mr. Saqib Mehboob, Mr. Adnan Muzaffar, and Mr. Farrukh Naveed. The help, advice, and leisure they provided to lift my spirits whenever I needed, gave me strength through the difficult times. Finally, I am thankful to COMSATS University Islamabad, Lahore Campus, Pakistan, for funding this work under the Split-Site PhD program and Lancaster University, United Kingdom, for providing an excellent research environment. Declaration I hereby declare that this dissertation or any part thereof has not previously been presented, unless otherwise indicated, in any form to the University or to any other body whether for the purposes of assessment, publication or for any other purpose. Save for any express acknowledgements and references cited in the work, I confirm that the contents of the work is the result of my own efforts and of no other person. The right of Muhammad Sharjeel is to be identified as author of this work. Muhammad Sharjeel Abstract Text reuse is the act of borrowing text (either verbatim or paraphrased) from an earlier written text. It could occur within the same language (mono-lingual) or across languages (cross-lingual) where the reused text is in a different language than the original text. Text reuse and its related problem, plagiarism (the unacknowl- edged reuse of text), are becoming serious issues in many fields and research shows that paraphrased and especially the cross-lingual cases of reuse are much harder to detect. Moreover, the recent rise in readily available multi-lingual content on the Web and social media has increased the problem to an unprecedented scale. To develop, compare, and evaluate automatic methods for mono- and cross- lingual text reuse and extrinsic (finding portion(s) of text that is reused from the original text) plagiarism detection, standard evaluation resources are of utmost im- portance. However, previous efforts on developing such resources have mostly fo- cused on English and some other languages. On the other hand, the Urdu language, which is widely spoken and has a large digital footprint, lacks resources in terms of core language processing tools and corpora. With this consideration in mind, this PhD research focuses on developing standard evaluation corpora, methods, and supporting resources to automatically detect mono-lingual (Urdu) and cross-lingual (English-Urdu) cases of text reuse and extrinsic plagiarism. This thesis contributes a mono-lingual (Urdu) text reuse corpus (COUNTER Corpus) that contains real cases of Urdu text reuse at document-level. Another con- tribution is the development of a mono-lingual (Urdu) extrinsic plagiarism corpus (UPPC Corpus) that contains simulated cases of Urdu paraphrase plagiarism. Eval- uation results, by applying a wide range of state-of-the-art mono-lingual methods on both corpora, shows that it is easier to detect verbatim cases than paraphrased ones. Moreover, the performance of these methods decreases considerably on real cases of reuse. A couple of supporting resources are also created to assist methods used in the cross-lingual (English-Urdu) text reuse detection. A large-scale multi-domain English-Urdu parallel corpus (EUPC-20) that contains parallel sentences is mined from the Web and several bi-lingual (English-Urdu) dictionaries are compiled using multiple approaches from different sources. Another major contribution of this study is the development of a large benchmark cross-lingual (English-Urdu) text reuse corpus (TREU Corpus). It contains English to Urdu real cases of text reuse at the document-level. A diversified range of methods are applied on the TREU Corpus to evaluate its usefulness and to show how it can be utilised in the development of automatic methods for measuring cross-lingual (English-Urdu) text reuse. A new cross-lingual method is also proposed that uses bi- lingual word embeddings to estimate the degree of overlap amongst text documents by computing the maximum weighted cosine similarity between word pairs. The overall low evaluation results indicate that it is a challenging task to detect cross- lingual real cases of text reuse, especially when the language pairs have unrelated scripts, i.e., English-Urdu. However, an improvement in the result is observed using a combination of methods used in the experiments. The research work undertaken in this PhD thesis contributes corpora, methods, and supporting resources for the mono- and cross-lingual text reuse and extrinsic plagiarism for a significantly under-resourced Urdu and English-Urdu language pair. It highlights that paraphrased and cross-lingual cross-script real cases of text reuse are harder to detect and are still an open issue. Moreover, it emphasises the need to develop standard evaluation and supporting resources for under-resourced languages to facilitate research in these languages. The resources that have been developed and methods proposed could serve as a framework for future research in other languages and language pairs. دورہ ال ا ہ ( ا ) ۔ ا زن ( ) دوى زن ( ا) ں دورہ ال ہ ا زن ۔ دورہ ال اور اس ، ( ہ دورہ ال)، د ں ر اور ا اور ص ا دورہ ال ں ۔ ، و اور آ دب ا اد ا اس د ۔ اور ا دورہ ال اور ر ( وہ ش ا دورہ ال ں) در ں ، از ، اور ، رى و ا ا ۔ ، اس ح و ں زدہ اى اور دوى زں ز ر ۔ دوى ف، اردو زن، و اور اس ا ا ڈ ذہ د ، دى چ و اور را ان ۔ اس ت ر ، ا ڈى اس رى را، ں، اور ون و ز د د (اردو) ا (اى اردو) دورہ ال اور ر ں ۔ ا (اردو) دورہ ال ر (ؤ ر) دو اردو دورہ ال ۔ ا اور (اردو) ر ر ( ر) ر اردو ا ۔ ، دوں را ا و ر ں ال ، ں ا زدہ آن ۔ آں، دورہ ال ں ان ں رد ۔ دو ون و ر ا (اى اردو) دورہ ال ں در ۔ ا ے ڈو اى اردو ا ر (اى ٢٠) ازى و ا اور د دو (اى اردو) ت ں ذر ذرا ۔ اس ا اور ا ا ا رى ا (اى اردو) دورہ ال ر ( آر اى ر) ر ۔ اس دو اى اردو دورہ ال ا ۔ آر اى ر ا ع ر ں اق اس اد اازہ اور ا (اى اردو) دورہ ال د ر ح ال ۔ ا ا دو ورڈ ا ال دوات درن اوور اازہ ں ڑوں زدہ زدہ و ۔ ر ا دورہ ال ا ں ا ا م ، ص ر زن ڑے ر ا ں، ، اى اردو۔ ، ت ال ں آ ااج ى د ۔ اس ا ڈى وع م ا و اردو اور اى اردو زن ڑى اور ا دورہ ال اور ر را، ، اور ون و ۔ ں ا اور ا ر ا دورہ ال ا ں اور اب اس ورت ۔ آں، و زں رى اور ون و ر ورت زور د ان زں وغ د ۔ و ر اور وہ د زں اور زں ڑوں ا ر م ۔ Contents 1 Introduction 1 1.1 Thesis focus . 5 1.2 Research goals . 6 1.3 Contributions . 7 1.4 Main findings . 10 1.5 Thesis structure . 11 1.6 Published work . 13 2 Literature Review 16 2.1 Plagiarism history . 17 2.2 Corpora for text reuse and extrinsic plagiarism .