1 Inteligenta Artificiala Universitatea Politehnica Bucuresti Anul universitar Adina Magda Florea

2 Curs nr. 13 Prelucrarea limbajului natural 2

3 Comunicare n Definitie: schimbul intentional de informatie generat de producerea si perceperea semnelor dintr-un sistem partajat de semne conventionale n Componentele comunicarii –intentie –generare –sinteza –perceptie –analiza –desambiguare –incorporare

4 Acte de comunicare n Teoria actelor de comunicare n locutie n ilocutie n prelocutie –asertive –directive –comisive –permisive –prohibitive –declarative –expresive Tipuri de agenti care comunica

5 Definire limbaj n Lexicon n Analiza lexicala n Gramatici n Analiza (pars oratoris) n Terminale, neterminale, reguli de rescriere n simbol de inceput n LHS  RHS n Analza semantica n Analiza pragmatica

6 Lexicon Noun  breeze | wumpus | ball Verb  is | see | smell | hit Adjective  right | left | smelly … Adverb  here | there | ahead … Pronoun  me | you | I | it RelPronoun  that | who Name  John | Mary Article  the | a | an Preposition  to | in | on Conjunction  and | or | but

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

8 Exemplu S  NP VP | S Conjunction S NP  Pronoun | Noun | Article Noun | NP PP | NP RelClause VP  Verb | VP NP | VP Adjective | VP PP | VP Adverb PP  Preposition NP RelClause  RelPronoun VP

9 Analiza sintactica –top-down parsing –bottom-up parsing –in adancime –pe nivel

10 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

11 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

12 Definite Clause Grammar (DCG) n Gramatici BNF - probleme n Utilizare LP n Gramatici cu clauze definite n DCG – gramatica; propozitie = clauza definita n neterminal = predicat de 1 argument n parsing = inferenta logica

13 In BNF S  NP VP In LP NP(s 1 )  VP(s 2 )  S(Append(s 1, s 2 )) BNF Noun  ball | book In LP (s = “ball”  s = “book”)  Noun(s)

BNF, DCG, Prolog BNFFOPLPROLOG S  NP VP NP  Noun Noun  stench Noun  wumpus VP  Verb Verb  smells Verb  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]).

15 Imbogatire DCG n Imbogatesc neterminale cu argumente suplimentare n Verifica corectitudinea gramaticala n Ataseseaza semantica n Adauga expresii / functii care se testeaza

16 Argument pt semantica DCGFOPL 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

18 Verificare corectitudine gramaticala n cazuri n subcategorii verbe: complementul pe care il poate accepta un verb n acord subiect predicat n etc. n Parametrizarea neterminalelor

Cazuri Nominativ (subjective) I take the busEu iau autobuzul You take the busTu iei autobuzul He takes the busEl ia autobuzul Acuzativ (objective) He gives me the bookImi da cartea S  NP(Subjective) VP NP(case)  Pronoun (case) | Noun | Article Noun //I VP  VP NP(Objective)//believe him VP  VP PP// turn to the right VP  VP Adjective VP  Verb PP  Preposition NP(Objective) Pronoun(Subjective)  I | you | he | she Pronoun(Objective)  me | you | him | her

20 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).

21 Subcategorii verbe n Lista de subcategorii: ce complemente accepta verbul n depinde de verb n S  NP(Subjective) VP(subcat) dar cazuri in care nu depinde n VP(subcat)  VP(subcat) PP n | 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 | she Pronoun(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).

25 Analiza pragmatica n Analiza semantica n Desambiguare n Interpretare pragmatica – utilizare si efect asupra ascultatorului n Indexical – refera situatia curenta n Anafora – refera obiecte deja mentionate

26 Ambiguitate n Lexicala – acelasi cuvant diverse intelesuri n Sintactica – arbori diferiti de analiza n Referentiala – referire la obiecte anerioare n Pragmatica – referire la loc, timp