Building a Hyponymy Lexicon with Hierarchical Structure Nph

Total Page:16

File Type:pdf, Size:1020Kb

Building a Hyponymy Lexicon with Hierarchical Structure Nph Unsupervised Lexical Acquisition: Proceedings of the Workshop of the ACL Special Interest Group on the Lexicon (SIGLEX), Philadelphia, July 2002, pp. 26-33. Association for Computational Linguistics. Building a hyponymy lexicon with hierarchical structure Sara Rydin [email protected] Centre for Speech Technology (CTT) KTH Stockholm, Sweden GSLT Abstract with new words and new uses of existing words. Our minimally supervised method for automatically Many lexical semantic relations, such as building partial hierarchies presents one way to the hyponymy relation, can be extracted solve the update problem. from text as they occur in detectable The objective of this project is to automatically syntactic constructions. This paper shows build a hierarchical hyponymy lexicon of noun how a hypernym-hyponym based lexi- phrases given large, part-of-speech tagged and lem- con for Swedish can be created directly matized corpora that are not restricted to one specific from a news paper corpus. An algorithm domain or topic. The lexicon will thus, reflect partial is presented for building partial hierarchi- hierarchical hyponymy structures that bring forward cal structures from non domain-specific extended hypernym-hyponym relations. texts. Section 2 describes previous work in the area of automatic acquisition of semantic lexicons, section 1 Introduction 3 elaborates on the principles for this work, and the Automatic acquisition of information on semantic remaining sections describe the implementation as relations from text has become more and more pop- well as the evaluation of the algorithm for building ular during the last ten to fifteen years. The goal has a hierarchical hyponymy lexicon. been to build various types of semantic lexicons for 2 Previous work use in natural language processing (NLP) systems, such as systems for information extraction/retrieval One of the first studies on acquisition of hyponymy or dialog systems. The lexicons are used to intro- relations was made by Hearst (1992). She found that duce extended semantic knowledge into the different certain lexico-syntactic constructions can be used as systems. indicators of the hyponymy relation between words Hand-built general-purpose lexicons, such as the in text. Example 1 shows a relation of this kind and WordNet (Fellbaum, 1998), have often been used to an example. The noun phrase ’ ¢¡¤£ ’ is a hypernym §¡©¨ ¤ ¢¡© §¡ bring semantic knowledge into NLP-systems. Two and ‘ ¥¦¥ ’ is one or more important problems concerning (semantic) lexicons (conjoined) noun phrases that are the hyponyms: are those of domain coverage and updates. Firstly, a ¢¡¤£%$ §¡©¨& ' © §¡"( §¡ "! # general-purpose lexicon cannot be expected to cover ¥¦¥ (1) all specific words used in different sub-domains. Therefore, the need for domain-specific lexicons has ‘such cars as Volvo, Seat and Ford’ recently been brought to the surface. Secondly, any lexicon, general or specific, has to Hearst proposed furthermore, that new syntactic pat- be updated from time to time, in order to keep up terns can be found in the following way: 1. Use the list of hypernyms-hyponyms found by hyponymy hierarchies, and for each hierarchy the the type of pattern described above to search for following criteria should be fulfilled: places in the corpus where the two expressions occur syntactically close to each other. Save the 1. A hierarchy has to be strict, so that every child syntactic examples. node in it can have one parent node only. 2. Examine all saved syntactic environments and 2. The words or phrases forming the nodes in a find new useful syntactic patterns. hierarchy should be disambiguated. 3. Use each new pattern to find more hypernym- 3. The organization in a hierarchy should be such hyponym examples. Continue at 1. that every child node is a hyponym (i.e. a type/kind) of its parent. Caraballo (1999) uses a hierarchical clustering tech- nique to build a hyponymy hierarchy of nouns. The Generally, principle 1-2 above are meant to pre- internal nodes are labeled by the syntactic construc- vent the hierarchies from containing ambiguity. The tions from Hearst (1992). Each internal node in the built-in ambiguity in the hyponymy hierarchy pre- hierarchy can be represented by up to three nouns. sented in (Caraballo, 1999) is primarily an effect of Work by Riloff & Shepherd (1997) and Char- the fact that all information is composed into one niak & Roark (1998) aims to build semantic lexicons tree. Part of the ambiguity could have been solved where the words included in each category or entry if the requirement of building one tree had been re- are related to, or are a member of the category. laxed. Sanderson & Croft (1999) build hierarchical Principle 2, regarding keeping the hierarchy structures of concepts on the basis of generality and ambiguity-free, is especially important, as we are specificity. They use material divided by different working with acquisition from a corpus that is not text categories and base the decision of subsumption domain restricted. We will have to constrain the way on term co-occurrence in the different categories. in which the hierarchy is growing in order to keep it A term x is said to subsume y if the documents in unambiguous. Had we worked with domain-specific which y occurs are a subset of the documents in data (see e.g. Morin and Jaquemin (1999)), it would which x occurs. The relations between concepts in have been possible to assume only one sense per their subsumption hierarchy are of different kinds word or phrase. (among other the hyponymy relation), and are un- The problem of building a hyponymy lexicon can labeled. be seen as a type of classification problem. In The work most similar to ours is that of Morin & this specific classification task, the hypernym is the Jacquemin (1999). They produce partial hyponymy class, the hyponyms are the class-members, and hierarchies guided by transitivity in the relation. But classifying a word means connecting it to its cor- while they work on a domain-specific corpus, we rect hypernym. The algorithm for classification and will acquire hyponymy data from a corpus which is for building hierarchies will be further described in not restricted to one domain. section 6. 3 Principles for building a hierarchical 4 Corpus and relevant terms lexicon This work has been implemented for Swedish, a This section will describe the principles behind our Germanic language. Swedish has frequent and pro- method for building the hierarchical structures in a ductive compounding, and morphology is richer lexicon. compared to, for example, English. Compounding As the objective is to build a nominal hyponymy affects the building of any lexical resource in that lexicon with partial hierarchical structures, there the number of different word types in the language are conditions that the hierarchical structures should is larger, and thus, the problems of data sparseness meet. The structures can each be seen as separate become more noticeable. In order to, at least partly, overcome the data sparseness problem, lemmatiza- ‘riksdagen, stadsfullmaktige¨ och liknande tion has been performed. However, no attempt has forsamlingar’¨ /lit. the Swedish Parliament, the been made to make a deeper analysis of compounds. town councilor and similar assemblies/ The corpus used for this research consists of §¡7 < ¢¡©8 "A /10© 243:3;26 §¡¤¨ ¤.F',>GH21IJKGL §¡¤£ 293,692 articles from the Swedish daily news pa- ¥ per ‘Dagens Nyheter’. The corpus was tokenized, (6) tagged and lemmatized. The tagger we used, im- ‘Osterleden¨ och Vasterleden,¨ de tva˚ mo- plemented by Megyesi (2001) for Swedish, is the torvagsprojekt’¨ /lit. the East way and the West TnT-tagger (Brants, 2000), trained on the SUC Cor- way, the two highway projects/ pus (Ejerhed et al., 1992). After preprocessing, the corpus was labeled for base noun phrases (baseNP). The basic assumption is that these construc- A baseNP includes optional determiners and/or pre- tions (henceforth called hh-constructions), yield modifiers, followed by nominal heads. pairs of terms between which the hyponymy relation Naturally, conceptually relevant terms, rather than holds. After a manual inspection of 20% of the noun phrases, should be placed in the lexicon and the total number of hh-constructions, it was estimated hierarchies. For reasons of simplification, though, that 92% of the hh-constructions give us correct the choice was made as to treat nominal heads with hyponymy relations. Erroneous hh-constructions premodifying nouns in genitive (within the limits of are mainly due to problems with, for example, the baseNP described above) as the relevant terms incorrect tagging, but also change in meaning due to include in the hierarchies. However, premodi- to PP-attachment. fiers describing amounts, such as ‘kilo’, are never 6 Building the hierarchical lexicon included in the relevant terms. To give an accurate description of the algorithm 5 Lexico-syntactic constructions for building the lexicon, the description here is di- Lexico-syntactic constructions are extracted vided into several parts. The first part describes from the corpus, in the fashion suggested by how hypernyms/hyponyms are grouped into classes, Hearst (1992). Five different Swedish constructions building an unambiguous lexicon base. The sec- has been chosen – constructions 2-6 below – as ond part describes how arrangement into hierarchi- a basis for building the lexicon (an example with cal structures is performed from this unambiguous the English translation is given below for each data. Last, we will describe how the lexicon is ex- construction)1 : tended. ++( ¢¡¤£ , §¡©' ' - §¡©¨. /10© 24353526 ¢¡7 ) * ) ¥¦¥ 6.1 Classification (2) There are two straightforward methods that can be ‘sadana˚ kanslor¨ som medkansla¨ och barmhartighet’¨ used to classify the data from the hh-constructions. /lit. such feelings as sympathy and compassion/ The first would be to group all hypernyms of the §¡©£ 8 9, §¡" ' ©7 §¡©¨. /10© 243:3;26& §¡7 ) ) * same lemma into one class. The second would be ¥ ¥¦¥ (3) to let each hypernym token (independently of their ‘exotiska frukter som papaya, pepino och mango’ lemma) initially build their own class, and then try /lit.
Recommended publications
  • The Generative Lexicon
    The Generative Lexicon James Pustejovsky" Computer Science Department Brandeis University In this paper, I will discuss four major topics relating to current research in lexical seman- tics: methodology, descriptive coverage, adequacy of the representation, and the computational usefulness of representations. In addressing these issues, I will discuss what I think are some of the central problems facing the lexical semantics community, and suggest ways of best ap- proaching these issues. Then, I will provide a method for the decomposition of lexical categories and outline a theory of lexical semantics embodying a notion of cocompositionality and type coercion, as well as several levels of semantic description, where the semantic load is spread more evenly throughout the lexicon. I argue that lexical decomposition is possible if it is per- formed generatively. Rather than assuming a fixed set of primitives, I will assume a fixed number of generative devices that can be seen as constructing semantic expressions. I develop a theory of Qualia Structure, a representation language for lexical items, which renders much lexical ambiguity in the lexicon unnecessary, while still explaining the systematic polysemy that words carry. Finally, I discuss how individual lexical structures can be integrated into the larger lexical knowledge base through a theory of lexical inheritance. This provides us with the necessary principles of global organization for the lexicon, enabling us to fully integrate our natural language lexicon into a conceptual whole. 1. Introduction I believe we have reached an interesting turning point in research, where linguistic studies can be informed by computational tools for lexicology as well as an appre- ciation of the computational complexity of large lexical databases.
    [Show full text]
  • THE LEXICON: a SYSTEM of MATRICES of LEXICAL UNITS and THEIR PROPERTIES ~ Harry H
    THE LEXICON: A SYSTEM OF MATRICES OF LEXICAL UNITS AND THEIR PROPERTIES ~ Harry H. Josselson - Uriel Weinreich /I/~ in discussing the fact that at one time many American scholars relied on either the discipline of psychology or sociology for the resolution of semantic problems~ comments: In Soviet lexicology, it seems, neither the tra- ditionalists~ who have been content to work with the categories of classical rhetoric and 19th- century historical semantics~ nor the critical lexicologists in search of better conceptual tools, have ever found reason to doubt that linguistics alone is centrally responsible for the investiga- tion of the vocabulary of languages. /2/ This paper deals with a certain conceptual tool, the matrix, which linguists can use for organizing a lexicon to insure that words will be described (coded) with consistency, that is~ to insure that questions which have been asked about certain words will be asked for all words in the same class, regardless of the fact that they may be more difficult to answer for some than for others. The paper will also dis- cuss certain new categories~ beyond those of classical rhetoric~ which have been introduced into lexicology. i. INTRODUCTION The research in automatic translation brought about by the introduction of computers into the technology has ~The research described herein has b&en supported by the In- formation Systems Branch of the Office of Naval Research. The present work is an amplification of a paper~ "The Lexicon: A Matri~ of Le~emes and Their Properties"~ contributed to the Conference on Mathematical Linguistics at Budapest-Balatonsza- badi, September 6-i0~ 1968.
    [Show full text]
  • CS474 Natural Language Processing Semantic Analysis Caveats Introduction to Lexical Semantics
    CS474 Natural Language Processing Semantic analysis Last class Assigning meanings to linguistic utterances – History Compositional semantics: we can derive the – Tiny intro to semantic analysis meaning of the whole sentence from the meanings of the parts. Next lectures – Max ate a green apple. – Word sense disambiguation Relies on knowing: » Background from linguistics – the meaning of individual words Lexical semantics – how the meanings of individual words combine to form » On-line resources the meaning of groups of words » Computational approaches [next class] – how it all fits in with syntactic analysis Caveats Introduction to lexical semantics Problems with a compositional approach Lexical semantics is the study of – the systematic meaning-related connections among – a former congressman words and – a toy elephant – the internal meaning-related structure of each word – kicked the bucket Lexeme – an individual entry in the lexicon – a pairing of a particular orthographic and phonological form with some form of symbolic meaning representation Sense: the lexeme’s meaning component Lexicon: a finite list of lexemes Lexical semantic relations: Dictionary entries homonymy right adj. located nearer the right hand esp. Homonyms: words that have the same form and unrelated being on the right when facing the same direction meanings – Instead, a bank1 can hold the investments in a custodial account as the observer. in the client’s name. – But as agriculture burgeons on the east bank2, the river will shrink left adj. located nearer to this side of the body even more. than the right. Homophones: distinct lexemes with a shared red n. the color of blood or a ruby. pronunciation – E.g.
    [Show full text]
  • The Art of Lexicography - Niladri Sekhar Dash
    LINGUISTICS - The Art of Lexicography - Niladri Sekhar Dash THE ART OF LEXICOGRAPHY Niladri Sekhar Dash Linguistic Research Unit, Indian Statistical Institute, Kolkata, India Keywords: Lexicology, linguistics, grammar, encyclopedia, normative, reference, history, etymology, learner’s dictionary, electronic dictionary, planning, data collection, lexical extraction, lexical item, lexical selection, typology, headword, spelling, pronunciation, etymology, morphology, meaning, illustration, example, citation Contents 1. Introduction 2. Definition 3. The History of Lexicography 4. Lexicography and Allied Fields 4.1. Lexicology and Lexicography 4.2. Linguistics and Lexicography 4.3. Grammar and Lexicography 4.4. Encyclopedia and lexicography 5. Typological Classification of Dictionary 5.1. General Dictionary 5.2. Normative Dictionary 5.3. Referential or Descriptive Dictionary 5.4. Historical Dictionary 5.5. Etymological Dictionary 5.6. Dictionary of Loanwords 5.7. Encyclopedic Dictionary 5.8. Learner's Dictionary 5.9. Monolingual Dictionary 5.10. Special Dictionaries 6. Electronic Dictionary 7. Tasks for Dictionary Making 7.1. Panning 7.2. Data Collection 7.3. Extraction of lexical items 7.4. SelectionUNESCO of Lexical Items – EOLSS 7.5. Mode of Lexical Selection 8. Dictionary Making: General Dictionary 8.1. HeadwordsSAMPLE CHAPTERS 8.2. Spelling 8.3. Pronunciation 8.4. Etymology 8.5. Morphology and Grammar 8.6. Meaning 8.7. Illustrative Examples and Citations 9. Conclusion Acknowledgements ©Encyclopedia of Life Support Systems (EOLSS) LINGUISTICS - The Art of Lexicography - Niladri Sekhar Dash Glossary Bibliography Biographical Sketch Summary The art of dictionary making is as old as the field of linguistics. People started to cultivate this field from the very early age of our civilization, probably seven to eight hundred years before the Christian era.
    [Show full text]
  • The Combinatory Morphemic Lexicon
    The Combinatory Morphemic Lexicon Cem Bozsahin∗ Middle East Technical University Grammars that expect words from the lexicon may be at odds with the transparent projection of syntactic and semantic scope relations of smaller units. We propose a morphosyntactic framework based on Combinatory Categorial Grammar that provides flexible constituency, flexible category consistency, and lexical projection of morphosyntactic properties and attachment to grammar in order to establish a morphemic grammar-lexicon. These mechanisms provide enough expressive power in the lexicon to formulate semantically transparent specifications without the necessity to confine structure forming to words and phrases. For instance, bound morphemes as lexical items can have phrasal scope or word scope, independent of their attachment characteristics but consistent with their semantics. The controls can be attuned in the lexicon to language-particular properties. The result is a transparent interface of inflectional morphology, syntax, and semantics. We present a computational system and show the application of the framework to English and Turkish. 1. Introduction The study presented in this article is concerned with the integrated representation and processing of inflectional morphology, syntax, and semantics in a unified grammar ar- chitecture. An important issue in such integration is mismatches in morphological, syntactic, and semantic bracketings. The problem was first noted in derivational mor- phology. Williams (1981) provided examples from English; the semantic bracketings in (1a–2a) are in conflict with the morphological bracketings in (1b–2b). (1) a. -ity b. hydro hydro electric electric -ity (2) a. -ing b. G¨odel G¨odel number number -ing If the problem were confined to derivational morphology, we could avoid it by making derivational morphology part of the lexicon that does not interact with gram- mar.
    [Show full text]
  • Changing the Rules: Why the Monolingual Learner's Dictionary Should Move Away from the Native-Speaker Tradition
    127 Changing the rules: Why the monolingual learner's dictionary should move away from the native-speaker tradition Michael Rundell This paper starts from a recognition that the reference needs of people learning English are not adequately met by existing monolingual learner's dictionaries (MLDs). Either the dictionaries themselves are deficient, or their target users have not yet learned how to use them effectively: whichever view one takes — and the truth is probably somewhere in between — it is difficult to escape the conclusion that the MLD's full potential as a language-learning resource has not yet been realized. This is recognized eg by Béjoint 1981: 219: "Monolingual dic­ tionaries are not used as fully as they should be ... many students are not even aware of the riches that their monolingual dictionaries contain" — a view which has been consistently borne out by any user-research we have conducted at Longman. There is a variety of responses to this situation. Compilers of MLDs may feel a certain exasperation with the 'ungrateful' students who fail to recognize the very real progress that has been made in adapting conventional dictionaries to their special needs. More positively, a growing awareness on the part of teachers of the importance of developing students' reference skills (eg Béjoint 1981: 220, Rossner 1985: 99 f., Whitcut 1986: 111) is complemented by a clear commit­ ment on the part of dictionary publishers to make their products as accessible and user-friendly as possible. These two developments seem to offer the beguiling prospect of a scenario in which ever more helpful MLDs are ever more skilfully exploited by their users — thus resolving, to everyone's satisfaction, the problem identified at the beginning of this paper.
    [Show full text]
  • Part 4: Lexical Semantics 2
    Natural Language Processing Part 4: lexical semantics 2 Marco Maggini Tecnologie per l'elaborazione del linguaggio Lexical semantics • A lexicon generally has a highly structured form ▫ It stores the meanings and uses of each word ▫ It encodes the relations between words and meanings • A lexeme is the minimal unit represented in the lexicon ▫ It pairs a stem (the orthographic/phonological form chosen to represent words) with a symbolic form for meaning representation (sense) • A dictionary is a kind of lexicon where meanings are expressed through definitions and examples son noun a boy or man in relation to either or both of his parents. • a male offspring of an animal. • a male descendant : the sons of Adam. • ( the Son) (in Christian belief) the second person of the Trinity; Christ. • a man considered in relation to his native country or area : one of Nevada's most famous sons. • a man regarded as the product of a particular person, influence, or environment : sons of the French Revolution. • (also my son) used by an elder person as a form of address for a boy or young man : “You're on private land, son.” 3 Marco Maggini Tecnologie per l'elaborazione del linguaggio Lexicons & dictionaries • Definitions in dictionaries exploit words and they may be circular (a word definition uses words whose definitions exploit that word) right adj. 1. of, relating to, situated on, or being the side of the body which is away from the side on which the heart is mostly located 2. located nearer to the right hand than to the left 3.
    [Show full text]
  • The Project, Its Ratiale and Processes,'Lrcludes A,Descrip-Tionf
    -QED 160 099,. AUTHOR Chenhall, Robert . TITLE The Onomastic Dctopus Repdif. No.3. INSTITUTION California State Univ., Fuller 5c ender .-SPONS N ational Endowment for puB DA NOTE 1 p-. BURS PcE- MF-$0. 3C-S1. Bins Post age DESCRI TORS, k-ctivities; *Catalcgivg; ctaaficetion, Ii'a.grams *Tnf ormati n Needs; *Museums; ru jects; *Subject.. Index Ter *Bysteus Analysis; TheSauti ABSTRACT Itoivities and information -in-museums and .a project titi ertaken,',Xithe Margaret -Woodbury. Strong-Museum to develop syStematic solutiOrp to' problems in cataloging museumcoliections-aze described. Museum-,eibtiwities Are grouped in three categories:41) initial.;--anisition -.:accession, registricn, identification, and restoration; (2)ongo- ng- -rearcb, exhibition, and conservation efforts; and (3) terminal_ -de-accessioniitg. Theongoing are the.,most lizportant'of the three y.pes.of _activities.. In order to carry out theseactivitieseffictitly, all. the information required for each- defined activity must be available at the right tine avd Iladet however- at the pre-sent time there are no systems cfnomenclature that are generally accepled as a basis for defining andidentifying - man-made artifacts.17,5 _.meet this need, this project focused on the creation of a the saur for use at the Strong Museum. This Standardized worpd_l'st, or lexicon, includes, words andphxases,.-and shows synonymous anhierarchical word ,-relationshipi and is not a panacea for all suseux. cataloging dependencies. While_it .1 qrpbleuls, it can serve as a commonstarting Loint. in. identificati activities which are crucial to the catalogin4 process. Asummaryof the project, its ratiale and processes,'Lrcludes a,descrip-tionf. the lexicon with examp es.(BIM) :/- * # *4$4*] x * * * * * * * ** Reproductions supped by EARS arethe hest that can be made the originaldocument.
    [Show full text]
  • Chapter 4 Lexicon Reading and Lecture Notes
    LING 650 Class Notes Ch.4 by Angelina Rubina & Laura Redden 1 CHAPTER 4 LEXICON READING AND LECTURE NOTES Lexicon – the language user’s mental dictionary. Do speakers memorize entire complex word-forms (e.g. readable, reads, washable)? their component morphemes (e.g. read, -able, -s, wash)? both? Three major positions on the content of the lexicon: a morpheme lexicon (corresponds to the morpheme-based model) contains simple, monomorphemic elements (i.e. roots and affixes) and idiosyncratic complex words (which are still created by rule); a strict word-form lexicon (consistent with the word-based model) contains all complex word-forms (predictable and idiosyncratic); a moderate word-form lexicon (consistent with the word-based model) potentially contains word-forms, morphemes and derived stems. Criticism of the chapter (according to Stan). Some of the problems set up in the chapter were sort of faux-problems used in order to make an argument and distinguish between derivation and inflection. This questions about the difference was used as a sort of “red herring” to lead you down the authors’ argumentation path. 4.1 A MORPHEME LEXICON Advantages of a morpheme lexicon Parallelism between syntax (sentences consist of words), morphology (words consist of morphemes), phonology (morphemes consist of phonemes). Elegant description of language structure: it is maximally economical because some word-forms follow the same morphological patterns in inflection, e.g. writer, reader + -s; in derivation (e.g. read + -er, -able). Problems for a morpheme lexicon Example Non-compositional (unpredictable) meaning Reader (British academic title) does not mean of some derived lexemes read + -er (as in read-er ‘any person who reads’) LING 650 Class Notes Ch.4 by Angelina Rubina & Laura Redden 2 Lack of morpheme segmentability: base modification German plurals e.g.
    [Show full text]
  • SLIDE – a Sentiment Lexicon of Common Idioms
    SLIDE – a Sentiment Lexicon of Common Idioms Charles Jochim, Francesca Bonin, Roy Bar-Haim, Noam Slonim IBM Research fcharlesj,[email protected], froybar,[email protected] Abstract Idiomatic expressions are problematic for most sentiment analysis approaches, which rely on words as the basic linguistic unit. Compositional solutions for phrase sentiment are not able to handle idioms correctly because their sentiment is not derived from the sentiment of the individual words. Previous work has explored the importance of idioms for sentiment analysis, but has not addressed the breadth of idiomatic expressions in English. In this paper we present an approach for collecting sentiment annotation of idiomatic multiword expressions using crowdsourcing. We collect 10 annotations for each idiom and the aggregated label is shown to have good agreement with expert annotations. We describe the resulting publicly available lexicon and how it captures sentiment strength and ambiguity. The Sentiment Lexicon of IDiomatic Expressions (SLIDE) is much larger than previous idiom lexicons. The lexicon includes 5,000 frequently occurring idioms, as estimated from a large English corpus. The idioms were selected from Wiktionary, and over 40% of them were labeled as sentiment-bearing. Keywords: Idiom, Lexicon, Sentiment Analysis 1. Introduction of magnitude larger than previous idiom sentiment lexi- cons and focuses specifically on the most frequently used Multiword expressions (MWE) are a key challenge in Natu- idioms.1 In creating this resource, we are somewhat ag- ral Language Processing (Sag et al., 2002). Among MWEs, nostic to the exact definition of idiom. We are more gener- idioms are often defined as non-compositional multiword ally interested in sentiment analysis that can handle MWEs.
    [Show full text]
  • Ontology and the Lexicon
    Ontology and the Lexicon Graeme Hirst Department of Computer Science, University of Toronto, Toronto M5S 3G4, Ontario, Canada; [email protected] Summary. A lexicon is a linguistic object and hence is not the same thing as an ontology, which is non-linguistic. Nonetheless, word senses are in many ways similar to ontological concepts and the relationships found between word senses resemble the relationships found between concepts. Although the arbitrary and semi-arbitrary distinctions made by natural lan- guages limit the degree to which these similarities can be exploited, a lexicon can nonetheless serve in the development of an ontology, especially in a technical domain. 1 Lexicons and lexical knowledge 1.1 Lexicons A lexicon is a list of words in a language—a vocabulary—along with some knowl- edge of how each word is used. A lexicon may be general or domain-specific; we might have, for example, a lexicon of several thousand common words of English or German, or a lexicon of the technical terms of dentistry in some language. The words that are of interest are usually open-class or content words, such as nouns, verbs, and adjectives, rather than closed-class or grammatical function words, such as articles, pronouns, and prepositions, whose behaviour is more tightly bound to the grammar of the language. A lexicon may also include multi-word expressions such as fixed phrases (by and large), phrasal verbs (tear apart), and other common expressions (merry Christmas!; teach someone ’s grandmother to suck eggs; Elvis has left the building). ! " Each word or phrase in a lexicon is described in a lexical entry; exactly what is included in each entry depends on the purpose of the particular lexicon.
    [Show full text]
  • A Tool Kit for Lexicon Building
    A TOOL KIT FOR LEXICON BUILDING Thomas E. Ahlswede Computer Science Department Illinois Institute of Technology Chicago, Illinois 6e616, USA The interactive lexicon builder will ABSTRACT be the basis for a fully automatic lexicon builder which uses Sager's Linguistic This paper describes a set of String Parser (LSP) to parse machine- interactive routines that can be used to readable text into a relational network create, maintain, and update a computer based on a modified version of Werner's lexicon. The routines are available to NTQ (Modification-Taxonomy-Queueing) the user as a set of commands resembling a schema. Initially this program will be simple operating system. The lexicon pro- applied to Webster's Seventh Collegiate duced by this system is based on lexi- Dictionary and the Longman Dictionary of cal-semantic relations, but is compatible Contemporary English, both of which are with a variety of other models of lexicon available in machine-readable form. structure. The lexicon builder is suit- able for the generation of moderate-sized vocabularies and has been used to construct a lexicon for a small medical expert system. A future version of the LEXICAL-SENANTIC RELATIONS lexicon builder will create a much larger lexicon by parsing definitions from The semantic component of the lexicon machine-readable dictionaries. produced by this system consists princi- pally of a network of lexical-semantic relations. That is, the meaning of a word in the lexicon is indicated as far as possible by its relationships with other words. These relations often have seman- tic content themselves and thus contribute INTRODUCTION to the definition of the words they link.
    [Show full text]