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Computational Linguistics

Computational Linguistics

Moustafashalabi
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Computational Linguistics

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  1. COMPUTATIONALLINGUISTICS Adapted & Compiled byDr.Moustafa M. Shalabymostafa.shalaby1970@gmail.comPhD Corpus LinguisticsFrom Dr.Dr.Athanasios N. KarasimosPhD in Linguistics National and Kapodistrian University of Athensakarasimos@gmail.com MoustafaShalaby

  2. COMPUTATIONAL LINGUISTICS CORPUS LINGUISTICS Introduction to Corpus Linguistics MoustafaShalaby

  3. OUTLINE What is and is not a corpus? Why use corpora? Corpora vs. intuitions A brief history of Corpus Linguistics Nature and applications of corpus-based studies MoustafaShalaby

  4. CORPUS: DEFINITION WHAT IS A CORPUS? • The word corpus comes from Latin (“body”) and the plural is corpora. • A corpus is a body of naturally occurring language (?). • …but rarely a random collection of text. • Corpora “are generally assembled with particular purposes in mind, and are often assembled to be (informally speaking) representative of some language or text type.” (Leech 1992). • “A corpus is a collection of (1) machine-readable (2) authentic texts (including transcripts of spoken data) which is (3) sampled to be (4) representative of a particular language or language variety.” (MXT 2006: 5) MoustafaShalaby

  5. WHATIS NOT A CORPUS? • A list of words is not a corpus. • Building blocks of language. • A text archive is not a corpus. • A random collection of texts. • A collection of citations is not a corpus. • A short quotation which contains a word or phrase that is the reason for its selection. MoustafaShalaby

  6. WHAT IS NOT A CORPUS? • A collection of quotations is not a corpus • A short selection from a text chosen on internal criteria by human beings • A text is not a corpus • Intending to be read in different ways • The Web is not a corpus • Its dimensions unknown, constantly changing, not designed from a linguistic perspective .Sinclair (2005) MoustafaShalaby

  7. WHAT IS A CORPUS FOR? • A corpus is made for the study of language in a broad sense • To test existing linguistic theory and hypotheses • To generate and verify new linguistic hypotheses • Beyond linguistics, to provide textual evidence in text-based humanities and social sciences subjects • The purpose is reflected in a well-designed corpus. MoustafaShalaby

  8. WHY USE CORPORA? • Even expert speakers have only a partial knowledge of a language. •A corpus can be more comprehensive and balanced. •Even expert speakers tend to notice the unusual and think of what is possible. •A corpus can show us what is common and typical. •Even expert speakers cannot quantify their knowledge of language. •A corpus can readily give us accurate statistics. MoustafaShalaby

  9. WHY USE CORPORA? • Even expert speakers cannot remember everything they know. • A corpus can store and recall all the information that has been stored in it. • Even experts' speakers cannot make up natural examples. • A corpus can provide us with a vast number of examples in real communication context. • Even expert speakers have prejudices and preferences, and every language has cultural connotations and underlying ideology. • • A corpus can give you more objective evidence. MoustafaShalaby

  10. WHY USE CORPORA? •Even expert speakers are not always available to be consulted. •A corpus can be made permanently accessible to all. •Even expert speakers cannot keep up with language change. •A constantly updated corpus can reflect even recent changes in the language. •Even expert speakers lack authority: they can be challenged by other expert speakers. •A corpus can encompass the actual language use of many expert speakers. MoustafaShalaby

  11. THE SCOPE OF CORPUS LINGUISTICS • Corpus makers or compilers. • Developers of tools for the analysis of corpora. • Descriptive linguists. • Exploiters of corpus-based linguistic descriptions for use in a variety of applications such as language learning and teaching, natural language processing by machine, including speech recognition and translation. MoustafaShalaby

  12. THE OTHER SIDE OF INTUITION • Intuitions are always useful in linguistics • To invent (grammatical, ungrammatical, or questionable) • example sentences for linguistic analysis • To make judgments about the acceptability /grammaticality • or meaning of an expression • To help with categorization MoustafaShalaby

  13. THE OTHER SIDE OF INTUITION Intuitions should be applied with caution •Possibly biased as they are likely to be influenced by one’s dialect or sociolect. •Introspective data is artificial and may not represent typical language use as one is consciously monitoring one’s language production. •Introspective data is decontextualized because it exists in the analyst’s mind rather than in any real linguistic context. Moustafa Shalaby

  14. THE OTHER SIDE OF INTUITION •Intuitions are not observable and verifiable by everyone as corpora are. •Excessive reliance on intuitions blinds the analyst to the realities of language usage because we tend to notice the unusual but overlook the commonplace •There are areas in linguistics where intuitions cannot be used reliably e.g. language variation, historical linguistics, register and style, first and second language acquisition. •Human beings have only the vaguest notion of the frequency of a construct or a word. Moustafa Shalaby

  15. BENEFITS OF CORPUS DATA • Corpus data is more reliable • A corpus pools together linguistic intuitions of a range of language speakers, which offsets the potential biases in intuitions of individual speakers • Corpus data is more natural • It is used in real communications instead of being invented specifically for linguistic analysis • Corpus data is contextualized • Attested language use which has already occurred in real linguistic context • Corpus data is quantitative • Corpora can provide frequencies and statistics readily • Corpus data can find differences that intuitions alone cannot perceive • E.g., synonyms totally, absolutely, utterly, completely, entirely Moustafa Shalaby

  16. CORPORA VS. INTUITIONS •Not necessarily antagonistic, but rather corroborate each other and can be gainfully viewed as being complementary. •Armchair linguists and corpus linguists “need each other. Or better, […] the two kinds of linguists, wherever possible, should exist in the same body.” (Fillmore 1992). •“Neither the corpus linguist of the 1950s, who rejected intuitions, nor the general linguist of the 1960s, who rejected corpus data, was able to achieve the interaction of data coverage and the insight that characterize the many successful corpus analyses of recent years.” (Leech 1991). •The key to using corpus data is to find the balance between the use of corpus data and the use of one’s intuitions. Moustafa Shalaby

  17. THE CORPUS METHODOLOGY •It is debatable whether CorLing is a methodology or a branch of linguistics •CorLing goes well beyond this methodological role and has become an independent discipline •In spite of the name, CorLing is indeed a methodology rather than an independent branch of linguistics in the same sense as phonetics, syntax, semantics or pragmatics •These latter areas of linguistics describe, or explain, a certain aspect of language use •Corpus linguistics, in contrast, is not restricted to a particular aspect of language - it can be employed to explore almost any area of linguistic research MoustafaShalaby

  18. THE HISTORY OF CORPUS A BRIEF HISTORY OF CORLING •The term corpus linguistics first appeared only in the early 1980s, but corpus-based language study has a substantial history. •The history of CorLing can be split into two periods: before and after Chomsky MoustafaShalaby

  19. B.C. HISTORY •Before Chomsky •Field linguists and linguists of the structuralist tradition used “shoebox corpora” – shoeboxes filled with paper slips. •Their methodology was essentially “corpus-based” in the sense that it was empirical and based on observed data. •The work of early corpus linguistics was underpinned by two fundamental, yet flawed assumptions. •The sentences of a natural language are finite. •The sentences of a natural language can be collected and enumerated. •Most linguists saw the “corpus” as the only source of linguistic evidence in the formation of linguistic theories. MoustafaShalaby

  20. CHOMSKY’S REVOLUTION •Chomsky revolution: Between 1957 and 1965 Chomsky changed the direction of linguistics from empiricism towards rationalism •“Any natural corpus will be skewed. Some sentences won’t occur because they are obvious, others because they are false, still others because they are impolite. The corpus, if natural, will be so wildly skewed that the description would be no more than a mere list.” (Chomsky 1962) •Our internal knowledge of language in human brain (competence) replaces observed data (performance) •Intuitions started to be relied on as evidence Xiao, R. (2008) MoustafaShalaby

  21. THE RETURN OF CORLING •Revival of CorLing •Corpus research was continued in a few centres (Brown, Lancaster) in the 60s-70s •The Brown University Standard Corpus of Present-day American English (Brown corpus) •Lancaster-Oslo-Bergen Corpus of BrE (LOB) •The hardware still imposed some restrictions until the real development started in the 1980s •The relation of corpora with computer technology rekindled interest in the corpus methodology •Since then, the number and size of corpora and corpus-based studies have increased dramatically •Nowadays, the corpus methodology enjoys widespread popularity, and has opened up or foregrounded many new areas of research MoustafaShalaby

  22. CORPUS LINGUISTICS AND THE OTHERS The Interaction of Corpus Linguistics AREAS THAT HAVE USED CORPORA MoustafaShalaby

  23. NATURE OF CORPUS-BASED APPROACH • It is empirical, analysing the actual patterns of use from natural texts • It utilises a large and principled collection of natural texts as the basis for analysis • It makes extensive use of computers for analysis, using both automatic and interactive techniques • It integrates both quantitative and qualitative analytical techniques (Biber et al. 1998: 4-5) MoustafaShalaby

  24. THE COMPUTER POWER Development of computer technology has revived CL. • Machine-readability is a de facto attribute of modern corpora. • Electronic corpora have advantages unavailable to their “shoebox” ancestors. • It is the use of computerized corpora, together with computer programs which facilitate linguistic analysis, that electronic corpora from early ‘drawer-cum-slip’ corpora. distinguishes modern • Computerized corpora can be processed and manipulated rapidly at minimal cost.• E.g. searching, selecting, sorting and formatting. MoustafaShalaby

  25. THE COMPUTER POWER • Computers can process machine-readable data accurately and consistently• Computers can avoid human bias in an analysis, thus making the result morereliable• Machine-readability allows further automatic processing to be performed on the corpus so that corpus texts can be enriched with various metadata and linguisticanalyses• Corpus markup and corpus annotation MoustafaShalaby

  26. WHAT CORPORA CANNOT DO • Corpora do not provide negative evidence. • Cannot tell us what is possible or not possible. • Can show what is central and typical in language. • Corpora can yield findings but rarely provide explanations for what is observed. • Interfacing other methodologies • The use of corpora as a methodology also defines the boundaries of any given study • Importance of amenable research questions • The findings based on a particular corpus only tell us what is true in that corpus • Generalization vs. representativeness MoustafaShalaby

  27. ASKING THE RIGHT QUESTION • Corpus linguistics as a methodology is only one of the (many) ways of doing things – “doing linguistics” • The usefulness of corpora depends upon the research question being investigated • “They are invaluable for doing what they do, and what they do not do must be done in another way.” (Hunston 2002: 20) • The development of the corpus-based approach as a tool in language studies has been compared to the invention of telescopes in astronomy • If it is ridiculous to criticize a telescope for not being a microscope, it is equally pointless to criticize the corpus-based approach for not doing what it is not intended to do • It is up to you to formulate research questions amenable to corpus-based investigation and to decide how to combine corpora with other resources MoustafaShalaby

  28. REFERENCES • Aijmer, K. 2009. Corpora and Language Teaching. Amsterdam/Philadelphia. J. Benjamins. • Aijmer, K., B. Altenberg. 1991. English Corpus Linguistics. Longman: London and New York. • Altenberg, B. 1998. ‚On the phraseology of spoken English: the evidence of recurrent word combinations‘ in Cowie, A.P. (ed) Phraseology:Theory Analysis and Applications. Oxford: Oxford University Press. • Altenberg, B. and Granger ,S. 2001. Grammatical and lexical patterning of make in student writing‘, Applied Linguistics 22(2): 173-194. • Aprijaskytė, R. and E. Pareigytė, 1982. Some lexical Difficulties for the Lithuanian Learner of English. Vilnius. • Aston, G. And Burnard, L. 1998. The BNC Handbook. Edinburgh: Edinburgh University Press. • Baker, M. 1993. ‘Corpus linguistics and translation studies: Implications and Applications’ in M. Baker, G. Francis and E. Tognini-Bonelli (eds)Text and technology: In Honour of John Sinclair. Amsterdam: John Benjamins, pp. 17-45. • Baker, M. 1996. ‘Corpus-based translation studies: The challenges that lie ahead’. In H. Somers (ed.) Terminology, LSP and Translation: Studiesin language engineering, in honour of Juan C. Sager. Amsterdam, John Benjamis, pp. 175-86. • Barnbrook, G. 1996. Language and Computers: A Practical introduction to the Computer Analysis of language”. Edinburgh University Press. • Biber, D. 1990. ‘Methodological issues regarding corpus-based analyses of of linguistic variation’. Literary and Linguistic Computing 5: 257-269. • Blum-Kulka, S. 1986. ‘Shifts of cohesion and coherence in translation’, in J.House and S. Blum-Kulka (eds) Interlingual and InterculturalCommunication: Discourse and cognition in translation and second language acquisition studies. Tubingen: Gunter Narr, pp. 17-35 MoustafaShalaby

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