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Inteligenta ArtificialaInteligenta Artificiala

Universitatea Politehnica BucurestiAnul universitar 2006-2007

Adina Magda Floreahttp://turing.cs.pub.ro/ia_07

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Curs nr. 13

Prelucrarea limbajului natural

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ComunicareComunicare Definitie: schimbul intentional de informatie generat

de producerea si perceperea semnelor dintr-un sistem partajat de semne conventionale

Componentele comunicarii– intentie– generare– sinteza

– perceptie– analiza– desambiguare– incorporare

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Acte de comunicareActe de comunicare Teoria actelor de comunicare locutie ilocutie prelocutie

– asertive– directive– comisive– permisive– prohibitive– declarative– expresive

Tipuri de agenti care comunica

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Definire limbajDefinire limbaj Lexicon Analiza lexicala Gramatici Analiza (pars oratoris) Terminale, neterminale, reguli de rescriere simbol de inceput LHS RHS

Analza semantica Analiza pragmatica

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Lexicon

Noun breeze | wumpus | ballVerb is | see | smell | hitAdjective right | left | smelly …Adverb here | there | ahead …Pronoun me | you | I | itRelPronoun that | whoName John | Mary Article the | a | an Preposition to | in | on Conjunction and | or | but

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GramaticaGramatica

Neterminale – diferite categorii din propozitie– sentence S– noun phrase NP– verb phrase VP– prepositional phrase PP– relative clause RelClause

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Exemplu

S NP VP | S Conjunction SNP Pronoun | Noun | Article Noun |

NP PP | NP RelClauseVP Verb | VP NP | VP Adjective |

VP PP | VP AdverbPP Preposition NPRelClause RelPronoun VP

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Analiza sintacticaAnaliza sintactica

– top-down parsing– bottom-up parsing

– in adancime– pe nivel

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Top-Down Parsing

"John hit the ball" 1. S 2. S NP, VP 3. S Noun, VP 4. S John, Verb, NP 5. S John, hit, NP 6. S John, hit, Article, Noun 7. S John, hit, the, Noun 8. S John, hit, the, ball

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Bottom-Up Parsing

1. John, hit, the, ball 2. Noun, hit, the, ball 3. Noun, Verb, the, ball 4. Noun, Verb, Article, ball 5. Noun, Verb, Article, Noun 6. NP, Verb, Article, Noun 7. NP, Verb, NP 8. NP, VP 9. S

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Definite Clause Grammar (DCG)Definite Clause Grammar (DCG)

Gramatici BNF - probleme Utilizare LP Gramatici cu clauze definite DCG – gramatica; propozitie = clauza

definita neterminal = predicat de 1 argument parsing = inferenta logica

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In BNF S NP VP

In LPNP(s1) VP(s2) S(Append(s1, s2))

BNFNoun ball | book

In LP(s = “ball” s = “book”) Noun(s)

BNF, DCG, PrologBNF, DCG, PrologBNF FOPL PROLOG

S NP VPNP NounNoun stenchNoun wumpusVP VerbVerb smellsVerb kills

NP(s1) VP(s2) S(append(s1,s2))Noun(s) NP(s)Verb(s) VP(s)(s = “stench” s = “wumpus”) Noun(s)(v = “smells” v = “kills”) Verb(v)

sentence([S1, S2]) :- np(S1), vp(S2).np(S):- noun(S).vp(S):- verb(S).noun(stench).noun(wumpus).verb(smells).verb(kills).?- sentence([wumpus, smells]).?-sentence([S1, S2]).

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Imbogatire DCGImbogatire DCG

Imbogatesc neterminale cu argumente suplimentare

Verifica corectitudinea gramaticala Ataseseaza semantica Adauga expresii / functii care se

testeaza

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Argument pt semanticaArgument pt semantica

DCG FOPL PROLOG

S(sem) NP(sem1) VP(sem2) {compose(sem1, sem2, sem)}

NP(s1, sem1) VP(s2, sem2) S(append(s1, s2)), compose(sem1, sem2, sem)

slide urmator

semantica compozitionala

The dog has legs. (caine parti picioare)The ball is yellow. (minge proprietate galbena)The ball is red. (mine proprietate rosie)The dog bites. (caine actiune musca)

sentence(S, Sem) :- np(S1, Sem1), vp(S2, Sem2), append(S1, S2, S),Sem = [Sem1 | Sem2].

np([S1, S2], Sem) :- article(S1), noun(S2, Sem).vp([S], Sem) :- verb(S, Sem1), Sem = [actiune, Sem1].vp([S1, S2], Sem) :- verb(S1,_), adjective(S2, Sem1), Sem = [proprietate, Sem1].vp([S1, S2], Sem) :- verb(S1,_), noun(S2, Sem1), Sem = [parti, Sem1].noun(dog,caine).noun(ball,ball).noun(legs,picioare).verb(bytes,musca).verb(is,este).verb(has,are).adjective(yellow,galbena).adjective(red,rosie).

?- sentence([the,ball,is,yellow],Sem).Sem = [minge, proprietate, galbena] Yes?- sentence([the,dog,bytes],Sem).Sem = [caine, actiune, musca] Yes?- sentence([is,dog,bytes],Sem).No?- sentence([the,dog,has,legs],Sem).Sem = [caine, parti, picioare] Yes

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Verificare corectitudine gramaticalaVerificare corectitudine gramaticala

cazuri subcategorii verbe: complementul pe

care il poate accepta un verb acord subiect predicat etc.

Parametrizarea neterminalelor

CazuriNominativ (subjective) I take the bus Eu iau autobuzulYou take the bus Tu iei autobuzulHe takes the bus El ia autobuzul Acuzativ (objective)He gives me the book Imi da cartea

S NP(Subjective) VPNP(case) Pronoun (case) | Noun | Article Noun

// IVP VP NP(Objective) // believe himVP VP PP // turn to the rightVP VP AdjectiveVP VerbPP Preposition NP(Objective)Pronoun(Subjective) I | you | he | shePronoun(Objective) me | you | him | her  

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sentence(S) :- np(S1,subjective), vp(S2),append(S1, S2, S).

np([S], Case) :- pronoun(S, Case).np([S], _ ) :- noun(S).np([S1, S2], _ ) :- article(S1), noun(S2).pronoun(i, subjective).pronoun(you, _ ).pronoun(he, subjective).pronoun(she, subjective).pronoun(me, objective).pronoun(him, objective).pronoun(her, objective).noun(ball).noun(stick).article(a).article(the).

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Subcategorii verbeSubcategorii verbe Lista de subcategorii: ce complemente accepta

verbul depinde de verb S NP(Subjective) VP(subcat)dar cazuri in care nu depinde VP(subcat) VP(subcat) PP | VP(subcat) Adverb I smell the

wumpus now

VP(subcat) {subcat = np} VP(np) NP(Objective)| {subcat = adj} VP(adj) Adjective| {subcat = pp} VP (pp) PP| Verb

smell [NP] smell a wumpus[Adjective] smell awfull[PP] smell like a wumpus

is [Adjective] is smelly[PP] is in box[NP] is a pit

give [NP, PP] give the gold in box to me[NP, NP] give me the gold

died [] died

S NP(Subjective) VP(subcat)

NP(case) Pronoun (case) | Noun | Article Noun

Pronoun(Subjective) I | you | he | shePronoun(Objective) me | you | him | her

VP(subcat) {subcat = np} VP(np) NP(Objective)| {subcat = adj} VP(adj) Adjective| {subcat = pp} VP (pp) PP| Verb| VP(subcat) PP| VP(subcat) Adverb

VP(subcat) {subcat = np} VP(np) NP(Objective)| {subcat = adj} VP(adj) Adjective| {subcat = pp} VP (pp) PP| Verb| VP(subcat) PP| VP(subcat) Adverb

sentence(S) :- np(S1,subjective), vp(S2, Subcat),append(S1, S2, S).

VP(subcat) VP(subcat) … !!!

vp(S, Subcat) :- Subcat = np, vp1(S1, np),np(S2, objective), append(S1, S2, S).

vp(S,Subcat) :- vp1(S1, Subcat), pp(S2), append(S1, S2, S). vp1([S],np):-verb(S).verb(give).verb(make).

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Analiza pragmaticaAnaliza pragmatica

Analiza semantica Desambiguare Interpretare pragmatica – utilizare si

efect asupra ascultatorului Indexical – refera situatia curenta Anafora – refera obiecte deja

mentionate

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AmbiguitateAmbiguitate

Lexicala – acelasi cuvant diverse intelesuri

Sintactica – arbori diferiti de analiza Referentiala – referire la obiecte

anerioare Pragmatica – referire la loc, timp