Presentation on theme: "Automatic Part-of-Speech Tagging of Arabic Text"— Presentation transcript:
1 Automatic Part-of-Speech Tagging of Arabic Text School of ComputingFACULTY OF ENGINEERINGAutomatic Part-of-Speech Tagging of Arabic Textالعَنْوَنَةُ الآلِيَّةُ لِنُصُوصِ اللُّغَةِ العَرَبِيَّةِMajdi SawalhaSupervisorDr. Eric Atwell
2 School of Computing Outline: Introduction Research focus and questions FACULTY OF ENGINEERINGOutline:IntroductionResearch focus and questionsA word about Arabic LanguageArabic Language CorporaGold standard for evaluationArabic Morphological Analysers and StemmersPrior-Knowledge broad-lexical resourceHybrid Part-of-Speech tagger of Arabic language
3 Introduction What is Part of Speech Tagging? What is a tag? School of ComputingFACULTY OF ENGINEERINGWhat is Part of Speech Tagging?What is a tag?What is the tagsets?Our AimHow to widen the scope of Arabic Part-of-Speech tagging, to develop a system which can process Arabic text in wide range of formats, domains, and genres of both vowelized and non-vowelized text ?
4 Research focus and questions School of ComputingFACULTY OF ENGINEERINGHow to widen the scope of Arabic Part-of-Speech tagging, to develop a system which can process Arabic text in wide range of formats, domains, and genres of both vowelized and non-vowelized text ?Research sub-questions:Can richer lexical resources derived from dictionaries and grammar text books improve the coverage of morphological analysis for wider range of Arabic text formats, domains and genres?How do we evaluate existing Part-of-Speech taggers and new Part-of-Speech tagger on a wider range of text formats, domains, genres, and vowelized and non-vowelized text?How do I make the best reuse of existing tagger components and methods?
5 Introduction Tagging Applications School of ComputingFACULTY OF ENGINEERINGTagging ApplicationsA good tagger can serve as a preprocessor.Large tagged text corpora are used as data for linguistic studies.Information technology applications;Text indexing and retrieval.Speech processing.
6 A word about Arabic Language School of ComputingFACULTY OF ENGINEERINGArabic language linguists classify words in Arabic into three main categories.Verbs: that word which denotes an action and has tense.Nouns: name of a person, place, or object and does not have any tense.Particles: that word of which cannot be understood without joining a noun or a verb or both.
7 Verb classifications A word about Arabic Language Verb الفعل School of ComputingFACULTY OF ENGINEERINGVerb classificationsVerbالفعلComplete Verbفعل تامIncomplete Verbفعل ناقصTransitive Verbفعل متعدِّIntransitive Verbفعل لازمActive Verbفعل معلومPassive Verbفعل مجهولVerbالفعلComplete Verbفعل تامIncomplete Verbفعل ناقصTransitive Verbفعل متعدِّIntransitive Verbفعل لازمActive Verbفعل معلومPassive Verbفعل مجهولVerbالفعلComplete Verbفعل تامIncomplete Verbفعل ناقصTransitive Verbفعل متعدِّIntransitive Verbفعل لازمActive Verbفعل معلومPassive Verbفعل مجهولVerbالفعلComplete Verbفعل تامIncomplete Verbفعل ناقصTransitive Verbفعل متعدِّIntransitive Verbفعل لازمActive Verbفعل معلومPassive Verbفعل مجهولVerbالفعلComplete Verbفعل تامIncomplete Verbفعل ناقصTransitive Verbفعل متعدِّIntransitive Verbفعل لازمActive Verbفعل معلومPassive Verbفعل مجهولVerbالفعلPerfect / Past Verbالفعل الماضيProgress Verbالفعل المضارعImperative Verbفعل أمر
8 A word about Arabic Language School of ComputingFACULTY OF ENGINEERINGNounsArabic language linguists distinguish between 21 types of nounsVerbal nounOriginal nounPronounPersonal nounDemonstrative nounJoining nounsInterrogative nounConditional nounGeneralization nounsAdverbPresent participlePast participleAdjectiveIncreased present participle.Comparing and contrasting entities, the comparative and the superlativeAdverb of placeAdverb of timeNoun of instrumentProper nounNoun of genusOrdinal number nounsVerb nounThe five nouns
9 A word about Arabic Language School of ComputingFACULTY OF ENGINEERINGParticlesParticlesMeaning ParticlesBuilding ParticlesInactive ParticlesActive ParticlesEffectsVerbJussiveSubjunctivePartial subjunctiveNounGenitive CaseVocativeExceptionBothConjunction
10 Arabic Language Tagset School of ComputingFACULTY OF ENGINEERINGEvaluating existing Arabic tagsets.Every researcher has developed a tagset. Either detailed or minimal tagset.A comparison of different tagsets will showThe number of tags used,The purpose of using the tagset.The source of information when designing the tagset.The errors in classifying tags into their categories.Designing a more reliable and multi-level tagset that varies from minimal tagset to more detailed one.
11 A word about Arabic Language School of ComputingFACULTY OF ENGINEERINGArabic Language challengesWriting constraints lead to ambiguities.Tokenization.Agglutination.Complex Morphology.Vowel Marks.Grammatical ambiguity2.8 in vowelized text and 5.6 in non-vowelized text
12 Tokenization What is a token? School of ComputingFACULTY OF ENGINEERINGWhat is a token?Main tokens are delimited by a white space or a punctuation mark( ، ؟ ؛ ! . etc) .Arabic Morphology allows words to be prefixed or suffixed with clitics.Clitics can be concatenated one after the other.Arabic clitics are not as easily recognizable.A single word can comprise up to four independent morphemes.Tokenizer is responsible for:Defining word boundaries.Demarcating clitics, multiword expressions, abbreviations and numbers.Affixes carry morpho-syntactic features- Tense - Person - Gender - Number)Clitics serve syntactic functions- Negation -Definition – Conjunction - Preposition
13 وَ لِ يَ كْتُبُ وُنَ هَا Tokenization Tokenization School of ComputingFACULTY OF ENGINEERINGMost Arabic words consist of stem/root and a combination of prefixes and suffixes.Root2- Prefix(es) + RootRoot + Suffix(es)4- Prefix(es) + Root + Suffix(es)Stem6- Prefix(es) + StemStem + Suffix(es)8- Prefix(es) + Stem + Suffix(es)كتبيكتبكتبهيكتبهكتابالكتابكتابهموكتابهمktbyktbktbhyktbhktAbAlktAbktAbhmwktAbhmWroteWriteWrote itWriting itBookThe bookTheir bookAnd their bookوَلِـيَـــكْـتُـبُــوُنَـهَـا [ wlyktbwnhA ] (And they write it)وَ * لِ * يَ * كْتُبُ * وُنَ * هَا (w*l*y*ktb*wn*hA)وَلِيَكْتُبُوُنَهَاConjunctionprepositionProgressive letterRootRelative Pronoun(Plural/Subject)(Object)
14 Vowels & Diacritical marks School of ComputingFACULTY OF ENGINEERINGArabic has 2 types of vowels1- Long vowels: Alif ا , waw و , yaa ي (part of Arabic letters)2- Short vowels: there small vowel marks which are not part of Arabic letters. These marks are placed above and below the Arabic letters.Arabic has other 5 diacritical marksNunation is the doubling of the short vowels used at the end of indefinite nounsSukun (absence of a vowel) consonant is not followed by a vowel.Gemination (Shadda) duplication of the consonant
15 Vowelization & Part-of-Speech Tagging School of ComputingFACULTY OF ENGINEERINGImportance of using diacritics in Arabic languageAdding semantic information to the wordsDetermining the correct tag to the word in the sentenceIndicating grammatical functions to the word(Mood, Aspect, Voice endings for verbs, Case endings for nouns).Indicating the correct pronunciation of word, correct syntactical analysis and removing the semantic confusion of Arabic readers.
16 Vowelization & Part-of-Speech Tagging School of ComputingFACULTY OF ENGINEERINGDiacritical marks affect the Part-of-Speech tag of the word and its meaning
17 Corpora or (Corpuses) Corpus Applications of Corpora School of ComputingFACULTY OF ENGINEERINGCorpusA collection of samples of texts that are selected and ordered according to explicit linguistic criteria in order to be used as a sample of the language.Applications of CorporaPrepare and format text to be used by search tools.Useful for linguist, teacher and learner. (advanced level)The study of syntactic structure.Corpus in lexicography used for developing good dictionaries.Used to train Machine Learning software for grammar analysis, word clustering, machine translation, …
18 Arabic Language Corpora School of ComputingFACULTY OF ENGINEERINGCorpus of Contemporary Arabic (CCA) [University of Leeds Corpus] (2004)Engineered by Latifa Al-Sulaiti & Eric Atwell; Written and some spoken; Around 1M words; TAFL; Websites and online magazinesFREE to download:Buckwalter Arabic CorpusWritten; 2.5 to 3 billion words, Lexicography;Public resources on the WebAn-Nahar Corpus (2001)Written;140M words; General research;An-Nahar newspaper (Lebanon)Al-Hayat Corpus (2002)Written;18.6M words; Language Engineering and Information Retrieval; Al-Hayat newspaper (Lebanon)Arabic Gigaword (2002)Written; Around 400M words; Natual language processing, information retrieval, language modelling; Agence France Presse, Al-Hayat news agency, An-Nahar news agency, Xinhua news agency
19 Gold Standard Evaluation Corpus School of ComputingFACULTY OF ENGINEERINGBuilding Gold Standard Evaluation CorpusDifferent text domains, formats and genres of both vowelised and non-vowelised text.The Qur’an.Newspaper text.Magazines.School books.Children’s books.Blogs (text in blogs can be in Arabic script or in roman letters transcription)Gold Standard will be checked by Arabic language scholars.
20 Gold Standard Evaluation Corpus School of ComputingFACULTY OF ENGINEERINGSample of Qur’an Gold Standard (vowelized)Sample of Newspaper Gold Standard (non-vowelized)Alif. Lam. Mim. Do men imagine that they will be left (at ease) because they say, We believe, and will not be tested with affliction? Lo! We tested those who were before them. Thus Allah knoweth those who are sincere, and knoweth those who feign. Or do those who do ill-deeds imagine that they can outstrip Us? Evil (for them) is that which they decide. Whoso looketh forward to the meeting with Allah (let him know that) Allah's reckoning is surely nigh, and He is the Hearer, the Knower. And whosoever striveth, striveth only for himself, for lo! Allah is altogether Independent of (His) creatures. And as for those who believe and do good works, We shall remit from them their evil deeds and shall repay them the best that they did. We have enjoined on man kindness to parents; but if they strive to make thee join with Me that of which thou hast no knowledge, then obey them not. Unto Me is your return and I shall tell you what ye used to do. And as for those who believe and do good works, We verily shall make them enter in among the righteous.Globalization will stay a hot topic of discussion for a long time. In this article, we consider in depth some of the questions raised by new writers who consider globalization as a new lifestyle for the modern man. Taking the lead from America, many writers describe the multi-ethnic and multicultural American life style as the ideal in the new global village where telecommunication, transportation, information systems and the media shorten the distances between disparate groups. Advocates of this point of view look forward to a new modern man, the Cosmopolitan man.
21 Arabic Morphological Analysers and Stemmers School of ComputingFACULTY OF ENGINEERINGEvaluating stemming and morphological analyzers.A comparison of three stemming algorithms has been done.Shereen Khoja Stemmer, Tim Buckwalter morphological analyzer and tri-literal root extraction algorithm.Four different fair evaluation measurements were applied.A combining by voting is used to combine results of different algorithms.The paper shows that more work in this field is required as the stemming algorithms failed to achieve accuracy rates more that 75% (sawalha & Atwell, 2008).
22 Prior-Knowledge broad-lexical resource of Arabic Language School of ComputingFACULTY OF ENGINEERING15 Arabic language dictionaries* are usedThe lexicon contains:roots and single words.Multi-word expressions.Idioms.Collocations requiring special part of speech assignment.Words with special part of speech tags.Meanings.I've seen it all..;)* Freely available from in MS-Word format
23 Prior-Knowledge broad-lexical resource of Arabic Language School of ComputingFACULTY OF ENGINEERINGLisan Al-Arab “ لسان العرب ” Arab tongueTaj Al-Arous min jawaher Al-Qamus “تاج العروس من جواهر القاموس ” Bride crown from the dictionaries jewels
24 Existing Arabic language Part-of-Speech taggers and reuse School of ComputingFACULTY OF ENGINEERINGEvaluating existing Part-of-Speech tagger components.Gold StandardFair measurementsMulti-level tagsetAnalyzing & re-implementing algorithms of Part-of-Speech taggers.Best tagger components need to be re-implemented, using Python.Python will simplify the integration of the Part-of-Speech tagger to the NLTK (Natural Language Toolkit).
25 Hybrid Part-of-Speech tagger School of ComputingFACULTY OF ENGINEERINGNovel algorithm leading to hybrid Part-of-Speech tagger for Arabic text which combines best components of existing taggers with novel resources and components.Integrating best tagger components togetherIntegrating Prior-knowledge lexical resourceIntegrating Morphological analyserUsing unsupervised learning algorithms to solve the problem of unknown words.
26 School of ComputingFACULTY OF ENGINEERINGشُكْرَاً