Learning Methods and Algorithms for Semantic Text Classification Across Multiple Domains

Total Page:16

File Type:pdf, Size:1020Kb

Learning Methods and Algorithms for Semantic Text Classification Across Multiple Domains Alma Mater Studiorum { Universit`adi Bologna DOTTORATO DI RICERCA IN Ingegneria Elettronica, Informatica e delle Telecomunicazioni Ciclo XXVII Settore concorsuale di afferenza: 09/H1 Settore scientifico disciplinare: ING-INF/05 LEARNING METHODS AND ALGORITHMS FOR SEMANTIC TEXT CLASSIFICATION ACROSS MULTIPLE DOMAINS Presentata da: Roberto Pasolini Coordinatore Dottorato Relatore Prof. Alessandro Vanelli-Coralli Prof. Gianluca Moro Correlatore Prof. Claudio Sartori Esame finale anno 2015 Abstract Information is nowadays a key resource: machine learning and data mining techniques have been developed to extract high-level information from great amounts of data. As most data comes in form of unstructured text in natural languages, research on text mining is currently very active and dealing with practical problems. Among these, text categorization deals with the automatic or- ganization of large quantities of documents in priorly defined tax- onomies of topic categories, possibly arranged in large hierarchies. In commonly proposed machine learning approaches, classifiers are automatically trained from pre-labeled documents: they can perform very accurate classification, but often require a consistent training set and notable computational effort. Methods for cross-domain text categorization have been pro- posed, allowing to leverage a set of labeled documents of one domain to classify those of another one. Most methods use advanced sta- tistical techniques, usually involving tuning of parameters. A first contribution presented here is a method based on nearest centroid classification, where profiles of categories are generated from the known domain and then iteratively adapted to the unknown one. De- spite being conceptually simple and having easily tuned parameters, this method achieves state-of-the-art accuracy in most benchmark datasets with fast running times. A second, deeper contribution involves the design of a domain- independent model to distinguish the degree and type of relatedness between arbitrary documents and topics, inferred from the differ- ent types of semantic relationships between respective representative words, identified by specific search algorithms. The application of this model is tested on both flat and hierarchical text categorization, where it potentially allows the efficient addition of new categories during classification. Results show that classification accuracy still requires improvements, but models generated from one domain are shown to be effectively able to be reused in a different one. To everyone who somehow supported me v Contents Introduction ix Contributions . xi Structure of the thesis . xiii Conventions . xiv Technical remarks . xiv 1 Data and Text Mining 1 1.1 Data mining . 1 1.1.1 Applications . 2 1.1.2 Machine learning . 3 1.2 Text mining . 5 1.2.1 Applications . 5 1.3 High-level text mining tasks . 7 1.3.1 Text categorization . 7 1.3.2 Sentiment analysis . 7 1.3.3 Text clustering . 8 1.3.4 Document summarization . 8 1.4 Natural language processing . 9 1.4.1 Part-Of-Speech Tagging . 10 1.4.2 Word Sense Disambiguation . 11 1.4.3 Other tasks . 12 2 General Techniques and Tools for Text Mining 13 2.1 Brief history . 13 vi Contents 2.2 Bag-of-Words representation . 14 2.2.1 Cosine similarity . 16 2.3 Extraction of features . 17 2.3.1 Lemmas . 17 2.3.2 Stems . 18 2.3.3 n-grams and phrases . 19 2.3.4 Concepts . 20 2.4 Term selection and weighting . 21 2.4.1 Basic word filtering . 21 2.4.2 Feature selection . 22 2.4.3 Term weighting . 23 2.5 Extraction of latent semantic information . 26 2.5.1 Latent semantic analysis . 26 2.5.2 Probabilistic models . 28 2.6 Linguistic and semantic knowledge bases . 29 2.6.1 WordNet . 30 3 Text Categorization 35 3.1 Problem description . 35 3.2 Variants . 36 3.2.1 Binary, single-label and multi-label classification . 36 3.2.2 Hierarchical classification . 37 3.3 Knowledge engineering approach . 39 3.4 Machine learning approach . 40 3.4.1 General setup . 41 3.4.2 Supervised term selection . 42 3.5 Common learning algorithms for text . 44 3.5.1 Na¨ıve Bayes . 44 3.5.2 Support Vector Machines . 47 3.5.3 Other methods . 49 3.6 Nearest centroid classification . 50 3.7 Hierarchical classification . 52 3.7.1 Big-bang approach . 53 3.7.2 Local classifiers . 53 3.8 Experimental evaluation . 54 3.8.1 Benchmark datasets . 55 3.8.2 Evaluation metrics . 58 Contents vii 4 Cross-Domain Text Categorization 65 4.1 Problem description . 65 4.1.1 Formalization . 67 4.1.2 Motivations . 67 4.2 State of the art . 68 4.2.1 Instance transfer . 68 4.2.2 Feature representation transfer . 69 4.2.3 Other related works . 70 4.3 Evaluation . 71 4.3.1 Common benchmark datasets . 71 4.4 Iterative refining of category representations . 72 4.4.1 Rationale . 75 4.4.2 Base method . 77 4.4.3 Computational complexity . 79 4.4.4 Results . 81 4.4.5 Variant with logistic regression . 91 4.4.6 Variant with termination by quasi-similarity . 95 4.4.7 Discussion . 99 5 A Domain-Independent Model for Semantic Relatedness 101 5.1 General idea . 101 5.1.1 Possible applications . 105 5.2 Related work . 106 5.3 General working scheme for text categorization . 108 5.3.1 Semantic knowledge base . 108 5.3.2 Model training . 109 5.3.3 Semantic matching algorithm . 111 5.3.4 Classification . 114 5.3.5 Computational complexity . 114 5.3.6 General experiment setup . 115 5.4 Search of semantic relationships . 117 5.4.1 Use of WordNet . 118 5.4.2 Existing approaches . 119 5.4.3 Hypernyms-based algorithm . 121 5.4.4 Extended search algorithm . 123 5.5 Flat categorization . 126 5.5.1 Example couples and category profiles . 126 5.5.2 Classification . 127 viii Contents 5.5.3 Experiment setup . 128 5.5.4 Experiment results . 130 5.6 Hierarchical categorization . 138 5.6.1 Couple labeling and selection . 138 5.6.2 Representation of categories . 140 5.6.3 Top-down classification algorithm . 141 5.6.4 Experiment setup . 142 5.6.5 Experiment results . 144 5.7 Discussion . 151 6 Conclusions 155 6.1 Ideas for future research . 157 A Network Security through Distributed Data Clustering 159 A.1 Distributed data mining . 159 A.2 Network intrusion detection systems . 160 A.3 General system model . 161 A.4 Implementation details . 162 A.5 Simulation setup . 164 A.6 Simulation results . 166 Bibliography 169 ix Introduction Nowadays, across many contexts, information of all kinds is produced at fast rates. Many things can be considered \information": the current tem- perature in a room, the details of a purchase in a store, a post on a social network and so on. From information, especially in large quantities, useful knowledge can be extracted: the details of many sales of a store may give useful indications about products often purchased together, while a col- lection of public messages about some product or service can reveal what people generally think about it. However, the extraction of useful knowl- edge from very large amounts of data is not always trivial, especially to be performed manually. Data mining research is dedicated to developing processes for automated extraction of useful, high-level information hidden within large amounts of data. It has many applications in business, finance, science, society and so on. Data mining is mostly based on machine learning, the study of algo- rithms to analyze a set of raw data and extract from it a knowledge model which encapsulates recurring patterns within it and allows to make more or less accurate predictions on future data. Machine learning algorithms can solve various task, such as classification of items or events according to prominent characteristics, such as classifying reviews of a product as positive or negative. Ordinary machine learning techniques work on structured data, where every piece of information is well distinguishable and computers can easily handle it. On the other way, unstructured data exist, which are easily interpreted by humans in small amounts, but not directly understandable by computers. A prominent part of such data is constituted by free text in x Introduction natural language, such as English or Italian, in units of different lengths, ranging from short messages on Twitter to publicly available whole books. Such text data, whose examples have been given above, can contain like other very valuable information, but automatic analysis is necessary to efficiently extract such knowledge in a usable form. Text mining is a branch of data mining studying techniques for auto- matic treatment of free text. This is generally achieved by processing text to represent it with structured forms, which can then be analyzed by usual learning algorithms. A very common form to efficiently represent every document of a large collection is the bag of words, a multiset of relevant words or other related features contained in the text. In this context, a quite common task is text categorization, consisting in the automatic organization of a possibly very large set of documents into distinct, meaningful categories. Categorization is usually carried out ac- cording to separate different topics discussed in document, but the general description involves also tasks like spam filtering in e-mail and identification of positive and negative reviews of a product. Organization of documents by topics can be useful in contexts like dividing books in sections, sepa- rating news articles by categories and organizing Web pages in hierarchical directories. Most methods for automatic text categorization are based on machine learning: given a training set of documents already labeled with respective correct categories, they are reduced to bags of words and, using suitable learning algorithms, a knowledge model is inferred from them, which is able to classify further documents within the same categories.
Recommended publications
  • Enhanced Thesaurus Terms Extraction for Document Indexing
    Enhanced Thesaurus Terms Extraction for Document Indexing Frane ari¢, Jan najder, Bojana Dalbelo Ba²i¢, Hrvoje Ekli¢ Faculty of Electrical Engineering and Computing, University of Zagreb Unska 3, 10000 Zagreb, Croatia E-mail:{Frane.Saric, Jan.Snajder, Bojana.Dalbelo, Hrvoje.Eklic}@fer.hr Abstract. In this paper we present an mogeneous due to diverse background knowl- enhanced method for the thesaurus term edge and expertise of human indexers. The extraction regarded as the main support to task of building semi-automatic and auto- a semi-automatic indexing system. The matic systems, which aim to decrease the enhancement is achieved by neutralising burden of work borne by indexers, has re- the eect of language morphology applying cently attracted interest in the research com- lemmatisation on both the text and the munity [4], [13], [14]. Automatic indexing thesaurus, and by implementing an ecient systems still do not achieve the performance recursive algorithm for term extraction. of human indexers, so semi-automatic sys- Formal denition and statistical evaluation tems are widely used (CINDEX, MACREX, of the experimental results of the proposed MAI [10]). method for thesaurus term extraction are In this paper we present a method for the- given. The need for disambiguation methods saurus term extraction regarded as the main and the eect of lemmatisation in the realm support to semi-automatic indexing system. of thesaurus term extraction are discussed. Term extraction is a process of nding all ver- batim occurrences of all terms in the text. Keywords. Information retrieval, term Our method of term extraction is a part of extraction, NLP, lemmatisation, Eurovoc.
    [Show full text]
  • An Evaluation of Machine Learning Approaches to Natural Language Processing for Legal Text Classification
    Imperial College London Department of Computing An Evaluation of Machine Learning Approaches to Natural Language Processing for Legal Text Classification Supervisors: Author: Prof Alessandra Russo Clavance Lim Nuri Cingillioglu Submitted in partial fulfillment of the requirements for the MSc degree in Computing Science of Imperial College London September 2019 Contents Abstract 1 Acknowledgements 2 1 Introduction 3 1.1 Motivation .................................. 3 1.2 Aims and objectives ............................ 4 1.3 Outline .................................... 5 2 Background 6 2.1 Overview ................................... 6 2.1.1 Text classification .......................... 6 2.1.2 Training, validation and test sets ................. 6 2.1.3 Cross validation ........................... 7 2.1.4 Hyperparameter optimization ................... 8 2.1.5 Evaluation metrics ......................... 9 2.2 Text classification pipeline ......................... 14 2.3 Feature extraction ............................. 15 2.3.1 Count vectorizer .......................... 15 2.3.2 TF-IDF vectorizer ......................... 16 2.3.3 Word embeddings .......................... 17 2.4 Classifiers .................................. 18 2.4.1 Naive Bayes classifier ........................ 18 2.4.2 Decision tree ............................ 20 2.4.3 Random forest ........................... 21 2.4.4 Logistic regression ......................... 21 2.4.5 Support vector machines ...................... 22 2.4.6 k-Nearest Neighbours .......................
    [Show full text]
  • Using Lexico-Syntactic Ontology Design Patterns for Ontology Creation and Population
    Using Lexico-Syntactic Ontology Design Patterns for ontology creation and population Diana Maynard and Adam Funk and Wim Peters Department of Computer Science University of Sheffield Regent Court, 211 Portobello S1 4DP, Sheffield, UK Abstract. In this paper we discuss the use of information extraction techniques involving lexico-syntactic patterns to generate ontological in- formation from unstructured text and either create a new ontology from scratch or augment an existing ontology with new entities. We refine the patterns using a term extraction tool and some semantic restrictions derived from WordNet and VerbNet, in order to prevent the overgener- ation that occurs with the use of the Ontology Design Patterns for this purpose. We present two applications developed in GATE and available as plugins for the NeOn Toolkit: one for general use on all kinds of text, and one for specific use in the fisheries domain. Key words: natural language processing, relation extraction, ontology generation, information extraction, Ontology Design Patterns 1 Introduction Ontology population is a crucial part of knowledge base construction and main- tenance that enables us to relate text to ontologies, providing on the one hand a customised ontology related to the data and domain with which we are con- cerned, and on the other hand a richer ontology which can be used for a variety of semantic web-related tasks such as knowledge management, information re- trieval, question answering, semantic desktop applications, and so on. Automatic ontology population is generally performed by means of some kind of ontology-based information extraction (OBIE) [1, 2]. This consists of identi- fying the key terms in the text (such as named entities and technical terms) and then relating them to concepts in the ontology.
    [Show full text]
  • LASLA and Collatinus
    L.A.S.L.A. and Collatinus: a convergence in lexica Philippe Verkerk, Yves Ouvrard, Margherita Fantoli, Dominique Longrée To cite this version: Philippe Verkerk, Yves Ouvrard, Margherita Fantoli, Dominique Longrée. L.A.S.L.A. and Collatinus: a convergence in lexica. Studi e saggi linguistici, ETS, In press. hal-02399878v1 HAL Id: hal-02399878 https://hal.archives-ouvertes.fr/hal-02399878v1 Submitted on 9 Dec 2019 (v1), last revised 14 May 2020 (v2) HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. L.A.S.L.A. and Collatinus: a convergence in lexica Philippe Verkerk, Yves Ouvrard, Margherita Fantoli and Dominique Longrée L.A.S.L.A. (Laboratoire d'Analyse Statistique des Langues Anciennes, University of Liège, Belgium) has begun in 1961 a project of lemmatisation and morphosyntactic tagging of Latin texts. This project is still running with new texts lemmatised each year. The resulting files have been recently opened to the interested scholars and they now count approximatively 2.500.000 words, the lemmatisation of which has been checked by a philologist. In the early 2.000's, Collatinus has been developed by Yves Ouvrard for teaching.
    [Show full text]
  • Experiments in Clustering Urban-Legend Texts
    How to Distinguish a Kidney Theft from a Death Car? Experiments in Clustering Urban-Legend Texts Roman Grundkiewicz, Filip Gralinski´ Adam Mickiewicz University Faculty of Mathematics and Computer Science Poznan,´ Poland [email protected], [email protected] Abstract is much easier to tap than the oral one, it becomes feasible to envisage a system for the machine iden- This paper discusses a system for auto- tification and collection of urban-legend texts. In matic clustering of urban-legend texts. Ur- this paper, we discuss the first steps into the cre- ban legend (UL) is a short story set in ation of such a system. We concentrate on the task the present day, believed by its tellers to of clustering of urban legends, trying to reproduce be true and spreading spontaneously from automatically the results of manual categorisation person to person. A corpus of Polish UL of urban-legend texts done by folklorists. texts was collected from message boards In Sec. 2 a corpus of 697 Polish urban-legend and blogs. Each text was manually as- texts is presented. The techniques used in pre- signed to one story type. The aim of processing the corpus texts are discussed in Sec. 3, the presented system is to reconstruct the whereas the clustering process – in Sec. 4. We manual grouping of texts. It turned out that present the clustering experiment in Sec. 5 and the automatic clustering of UL texts is feasible results – in Sec. 6. but it requires techniques different from the ones used for clustering e.g. news ar- 2 Corpus ticles.
    [Show full text]
  • Removing Boilerplate and Duplicate Content from Web Corpora
    Masaryk University Faculty}w¡¢£¤¥¦§¨ of Informatics !"#$%&'()+,-./012345<yA| Removing Boilerplate and Duplicate Content from Web Corpora Ph.D. thesis Jan Pomik´alek Brno, 2011 Acknowledgments I want to thank my supervisor Karel Pala for all his support and encouragement in the past years. I thank LudˇekMatyska for a useful pre-review and also for being so kind and cor- recting typos in the text while reading it. I thank the KrdWrd team for providing their Canola corpus for my research and namely to Egon Stemle for his help and technical support. I thank Christian Kohlsch¨utterfor making the L3S-GN1 dataset publicly available and for an interesting e-mail discussion. Special thanks to my NLPlab colleagues for creating a great research environment. In particular, I want to thank Pavel Rychl´yfor inspiring discussions and for an interesting joint research. Special thanks to Adam Kilgarriff and Diana McCarthy for reading various parts of my thesis and for their valuable comments. My very special thanks go to Lexical Computing Ltd and namely again to the director Adam Kilgarriff for fully supporting my research and making it applicable in practice. Last but not least I thank my family for all their love and support throughout my studies. Abstract In the recent years, the Web has become a popular source of textual data for linguistic research. The Web provides an extremely large volume of texts in many languages. However, a number of problems have to be resolved in order to create collections (text corpora) which are appropriate for application in natural language processing. In this work, two related problems are addressed: cleaning a boilerplate and removing duplicate and near-duplicate content from Web data.
    [Show full text]
  • The State of (Full) Text Search in Postgresql 12
    Event / Conference name Location, Date The State of (Full) Text Search in PostgreSQL 12 FOSDEM 2020 Jimmy Angelakos Senior PostgreSQL Architect Twitter: @vyruss https://www.2ndQuadrant.com FOSDEM Brussels, 2020-02-02 Contents ● (Full) Text Search ● Indexing ● Operators ● Non-natural text ● Functions ● Collation ● Dictionaries ● Other “text” types ● Examples ● Maintenance https://www.2ndQuadrant.com FOSDEM Brussels, 2020-02-02 Your attention please Allergy advice ● This presentation contains linguistics, NLP, Markov chains, Levenshtein distances, and various other confounding terms. ● These have been known to induce drowsiness and inappropriate sleep onset in lecture theatres. https://www.2ndQuadrant.com FOSDEM Brussels, 2020-02-02 What is Text? (Baby don’t hurt me) ● PostgreSQL character types – CHAR(n) – VARCHAR(n) – VARCHAR, TEXT ● Trailing spaces: significant (e.g. for LIKE / regex) ● Storage – Character Set (e.g. UTF-8) – 1+126 bytes → 4+n bytes – Compression, TOAST https://www.2ndQuadrant.com FOSDEM Brussels, 2020-02-02 What is Text Search? ● Information retrieval → Text retrieval ● Search on metadata – Descriptive, bibliographic, tags, etc. – Discovery & identification ● Search on parts of the text – Matching – Substring search – Data extraction, cleaning, mining https://www.2ndQuadrant.com FOSDEM Brussels, 2020-02-02 Text search operators in PostgreSQL ● LIKE, ILIKE (~~, ~~*) ● ~, ~* (POSIX regex) ● regexp_match(string text, pattern text) ● But are SQL/regular expressions enough? – No ranking of results – No concept of language – Cannot be indexed ● Okay okay, can be somewhat indexed* ● SIMILAR TO → best forget about this one https://www.2ndQuadrant.com FOSDEM Brussels, 2020-02-02 What is Full Text Search (FTS)? ● Information retrieval → Text retrieval → Document retrieval ● Search on words (on tokens) in a database (all documents) ● No index → Serial search (e.g.
    [Show full text]
  • A Diachronic Treebank of Russian Spanning More Than a Thousand Years
    Proceedings of the 12th Conference on Language Resources and Evaluation (LREC 2020), pages 5251–5256 Marseille, 11–16 May 2020 c European Language Resources Association (ELRA), licensed under CC-BY-NC A Diachronic Treebank of Russian Spanning More Than a Thousand Years Aleksandrs Berdicevskis1, Hanne Eckhoff2 1Språkbanken (The Swedish Language Bank), Universify of Gothenburg 2Faculty of Medieval and Modern Languages, University of Oxford [email protected], [email protected] Abstract We describe the Tromsø Old Russian and Old Church Slavonic Treebank (TOROT) that spans from the earliest Old Church Slavonic to modern Russian texts, covering more than a thousand years of continuous language history. We focus on the latest additions to the treebank, first of all, the modern subcorpus that was created by a high-quality conversion of the existing treebank of contemporary standard Russian (SynTagRus). Keywords: Russian, Slavonic, Old Church Slavonic, treebank, diachrony, conversion and a richer inventory of syntactic relation labels. 1. Introduction Secondary dependencies are used to indicate external The Tromsø Old Russian and OCS Treebank (TOROT, subjects, for example in control structures, and to indicate Eckhoff and Berdicevskis 2015) has been available in shared dependents, for example in structures with various releases since its beginnings in 2013, and its East coordinated verbs. Empty nodes are allowed to give more Slavonic part now contains approximately 230K words.1 information on elliptic structures and asyndetic This paper describes the TOROT 20200116 release,2 which coordination. The empty nodes are limited to verbs and adds a conversion of the SynTagRus treebank. Former conjunctions, the scheme does not allow empty nominal TOROT releases consisted of Old East Slavonic and nodes.
    [Show full text]
  • Download in the Conll-Format and Comprise Over ±175,000 Tokens
    Integrated Sequence Tagging for Medieval Latin Using Deep Representation Learning Mike Kestemont1, Jeroen De Gussem2 1 University of Antwerp, Belgium 2 Ghent University, Belgium *Corresponding author: [email protected] Abstract In this paper we consider two sequence tagging tasks for medieval Latin: part-of-speech tagging and lemmatization. These are both basic, yet foundational preprocessing steps in applications such as text re-use detection. Nevertheless, they are generally complicated by the considerable orthographic variation which is typical of medieval Latin. In Digital Classics, these tasks are traditionally solved in a (i) cascaded and (ii) lexicon-dependent fashion. For example, a lexicon is used to generate all the potential lemma-tag pairs for a token, and next, a context-aware PoS-tagger is used to select the most appropriate tag-lemma pair. Apart from the problems with out-of-lexicon items, error percolation is a major downside of such approaches. In this paper we explore the possibility to elegantly solve these tasks using a single, integrated approach. For this, we make use of a layered neural network architecture from the field of deep representation learning. keywords tagging, lemmatization, medieval Latin, LSTM, deep learning INTRODUCTION Latin —and its historic variants in particular— have long been a topic of major interest in Natural Language Processing [Piotrowksi 2012]. Especially in the community of Digital Humanities, the automated processing of Latin texts has always been a popular research topic. In a variety of computational applications, such as text re-use detection [Franzini et al, 2015], it is desirable to annotate and augment Latin texts with useful morpho-syntactical or lexical information, such as lemmas.
    [Show full text]
  • Lemmagen: Multilingual Lemmatisation with Induced Ripple-Down Rules
    Journal of Universal Computer Science, vol. 16, no. 9 (2010), 1190-1214 submitted: 21/1/10, accepted: 28/4/10, appeared: 1/5/10 © J.UCS LemmaGen: Multilingual Lemmatisation with Induced Ripple-Down Rules MatjaˇzJurˇsiˇc (Joˇzef Stefan Institute, Ljubljana, Slovenia [email protected]) Igor Mozetiˇc (Joˇzef Stefan Institute, Ljubljana, Slovenia [email protected]) TomaˇzErjavec (Joˇzef Stefan Institute, Ljubljana, Slovenia [email protected]) Nada Lavraˇc (Joˇzef Stefan Institute, Ljubljana, Slovenia and University of Nova Gorica, Nova Gorica, Slovenia [email protected]) Abstract: Lemmatisation is the process of finding the normalised forms of words appearing in text. It is a useful preprocessing step for a number of language engineering and text mining tasks, and especially important for languages with rich inflectional morphology. This paper presents a new lemmatisation system, LemmaGen, which was trained to generate accurate and efficient lemmatisers for twelve different languages. Its evaluation on the corresponding lexicons shows that LemmaGen outperforms the lemmatisers generated by two alternative approaches, RDR and CST, both in terms of accuracy and efficiency. To our knowledge, LemmaGen is the most efficient publicly available lemmatiser trained on large lexicons of multiple languages, whose learning engine can be retrained to effectively generate lemmatisers of other languages. Key Words: rule induction, ripple-down rules, natural language processing, lemma- tisation Category: I.2.6, I.2.7, E.1 1 Introduction Lemmatisation is a valuable preprocessing step for a large number of language engineering and text mining tasks. It is the process of finding the normalised forms of wordforms, i.e. inflected words as they appear in text.
    [Show full text]
  • Language Technology Meets Documentary Linguistics: What We Have to Tell Each Other
    Language technology meets documentary linguistics: What we have to tell each other Language technology meets documentary linguistics: What we have to tell each other Trond Trosterud Giellatekno, Centre for Saami Language Technology http://giellatekno.uit.no/ . February 15, 2018 . Language technology meets documentary linguistics: What we have to tell each other Contents Introduction Language technology for the documentary linguist Language technology for the language society Conclusion . Language technology meets documentary linguistics: What we have to tell each other Introduction Introduction I Giellatekno: started in 2001 (UiT). Research group for language technology on Saami and other northern languages Gramm. modelling, dictionaries, ICALL, corpus analysis, MT, ... I Trond Trosterud, Lene Antonsen, Ciprian Gerstenberger, Chiara Argese I Divvun: Started in 2005 (UiT < Min. of Local Government). Infrastructure, proofing tools, synthetic speech, terminology I Sjur Moshagen, Thomas Omma, Maja Kappfjell, Børre Gaup, Tomi Pieski, Elena Paulsen, Linda Wiechetek . Language technology meets documentary linguistics: What we have to tell each other Introduction The most important languages we work on . Language technology meets documentary linguistics: What we have to tell each other Language technology for the documentary linguist Language technology for documentary linguistics ... Language technology meets documentary linguistics: What we have to tell each other Language technology for the documentary linguist ... what’s in it for the language community I work for? I Let’s pretend there are two types of language communities: 1. Language communities without plans for revitalisation or use in domains other than oral use 2. Language communities with such plans . Language technology meets documentary linguistics: What we have to tell each other Language technology for the documentary linguist Language communities without such plans I Gather empirical material and do your linguistic analysis I (The triplet: Grammar, text collection and dictionary) I ..
    [Show full text]
  • A 500 Million Word POS-Tagged Icelandic Corpus
    A 500 Million Word POS-Tagged Icelandic Corpus Thomas Eckart1, Erla Hallsteinsdóttir², Sigrún Helgadóttir³, Uwe Quasthoff1, Dirk Goldhahn1 1Natural Language Processing Group, University of Leipzig, Germany ² Department of Language and Communication, University of Southern Denmark, Odense, Denmark ³ The Árni Magnússon Institute for Icelandic Studies, Reykjavík, Iceland Email: {teckart, quasthoff, dgoldhahn}@informatik.uni-leipzig.de, [email protected], [email protected] Abstract The new POS-tagged Icelandic corpus of the Leipzig Corpora Collection is an extensive resource for the analysis of the Icelandic language. As it contains a large share of all Web documents hosted under the .is top-level domain, it is especially valuable for investigations on modern Icelandic and non-standard language varieties. The corpus is accessible via a dedicated web portal and large shares are available for download. Focus of this paper will be the description of the tagging process and evaluation of statistical properties like word form frequencies and part of speech tag distributions. The latter will be in particular compared with values from the Icelandic Frequency Dictionary (IFD) Corpus. Keywords: Corpus Creation, Part-of-Speech Tagging, Grammar and Syntax 1. History of the Icelandic Corpus Larger Icelandic corpora have been part of the Leipzig Corpora Collection (LCC) since 2005. The aim of the project is to generate large monolingual corpora based on various material of different genre, where the biggest resources are Web texts provided by the National and University Library of Iceland from autumn 2005 and autumn 2010 (approx. 33 million sentences). Moreover, additional newspaper texts (2 million sentences) and the complete Icelandic Wikipedia is included.
    [Show full text]