计算机语言英文版.ppt

1 IntroductiontoComputationalLinguistics EleniMiltsakakiAUTHFall2005 Lecture4 2 What stheplanfortoday BriefreviewofChomsky sHierarchyoflanguagesTreeAdjoiningGrammarLexicalFunctionalGrammarNexttime Head drivenPhraseStructureGrammarReadings Parsing verybrief ParsinginpsycholinguisticsExamplesofTAGderivations 3 Chomskyhierarchy review ContainmenthierarchyofclassesofformalgrammarsthatgenerateformallanguagesType0 unrestricted includeallformalgrammarsAnystringofterminalsandnon terminalstoanystringofterminalsandnon terminalsType1 contextsensitiveA anystringofterminalsandnon terminalsType2 contextfree thetheoreticalbasisforthesyntaxofmostprogramminglanguages A a A BaType3 regulargrammarsA a 4 Lexicalizedgrammars Treeadjoininggrammar TAG TheXTAGproject www cis upenn edu xtag home html TheTAGworkshops www cs rutgers edu TAG 7 Lexicalfunctionalgrammar LFG LFGresourcesite http www essex ac uk linguistics LFG LFGconferences http lfg05 uib no Head drivenphrasestructuregrammar HPSG HPSGresourcesite http hpsg stanford edu HPSGconferences http hpsg2005 di fc ul pt 5 Treeadjoininggrammars IntroducedbyJoshi Levy Takahashi 1975 andJoshi 1985 LinguisticallymotivatedTreegeneratinggrammar generatestreestructuresnotjuststrings Example Iwanthimtoleave IpromisedhimtoleaveAllowsfactoringrecursionfromthestatementoflinguisticconstraints dependencies thussimplifyinglinguisticdescription Kroch Joshi1985 FormallymotivatedA new classofgrammarsthatdescribemildlycontextsensitivelanguages Joshietal1991 6 TheTAGformalism ConceptsLocalityandrecursionLexicalizationElementaryobjectsInitialtreesAuxiliarytreesOperationsSubstitutionAdjunction 7 Localityandrecursion StretchingdependenciesWhodoyouliket WhodoesJohnthinkthatyouliket WhodoesJohnthinkthatMarysaidthatyouliket Alsocompare JohntriedtopleaseMaryJohnseemstolikeMary 8 Lexicalization Inalexicalizedgrammareachelementarystructureisassociatedwithalexicalitem calledits anchor 9 Elementarytrees 10 Operation1 Substitution 11 12 13 TreeFamilies 14 Verbsandparticles 15 Wh extraction 16 Operation2 Adjunction 17 Operation2 Adjunction 18 Derivedandderivationtrees 19 ReferenceforTAGs Treeadjoininggrammars Formalisms LinguisticAnalysisandProcessingbyAnneAbeill andOwenRambow http cslipublications stanford edu site 1575862522 html 20 LexicalFunctionalGrammar FirstintroducedbyKaplan Bresnan 1982 AtheoryofgrammarSyntax howwordscombinetomakeupsentences Semantics howandwhywordsandcombinationsofwordsmeanwhattheymean 21 BasiccomponentsofLFG TwoparallellevelsofsyntacticrepresentationConstituentstructure c structure Functionalstructure f structure C structureshavetheformofcontext freephrasestructuretreesF structuresaresetsofpairsofattributesandvalues attributesmaybefeatures suchastenseandgender orfunctions suchassubjectandobject 22 Structure structuraldescriptionandcorrespondence Allowablec structuresforasentencearedefinedbycontext freerewriterulesThedescriptionofanappropriatef structureisderivedfromfunctionalannotationsontothec structurerulesTointerpretfunctionalannotationsKapl