1. Inteligenta Artificiala
Universitatea Politehnica Bucuresti Anul universitar
Adina Florea
si curs.cs.pub.ro

2. Curs nr. 13
Prelucrarea limbajului natural 2

3. Comunicare
Definitie: schimbul intentional de informatie generat de producerea si perceperea semnelor dintr-un sistem partajat de semne conventionale
Componentele comunicarii
Intentie: decide Emitator
Generare: formeaza
Sinteza: produce
Perceptie: percepe (P1 ..Pn) Receptor
Analiza: lexic, sintactic, semantic, pragmatic
eliminare ambiguitate: alege Pi
Incorporare: convingere Pi
Limbaj de reprezentare intern
Limbaj de comunicare

4. Acte de comunicare Un act de comunicare: Categorii ilocutionale
J. Austin - How to do things with words, 1962, J. Searle - Speech acts, 1969
Un act de comunicare:
locutie = fraza spusa de locutor
illocutie = intelesul dorit spre a fi comunicat de locutor (performativa)
prelocutie = actiunea care rezulta din locutie
Maria i-a spus lui Gigel: "Te rog inchide usa"
locutie illocutie
prelocutie: usa inchisa
Categorii ilocutionale
Asertive
Directive
Comisive (angajamente)
Permisive (permit)
Prohibitive (interzic)
Declarative
Expresive

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

10. Top-Down Parsing "John hit the ball" 1. S 2. S  NP, VP 3
Top-Down Parsing "John hit the ball" S S  NP, VP S  Noun, VP S  John, Verb, NP S  John, hit, NP S  John, hit, Article, Noun S  John, hit, the, Noun S  John, hit, the, ball

11. Bottom-Up Parsing. 1. John, hit, the, ball 2. Noun, hit, the, ball 3
Bottom-Up Parsing John, hit, the, ball Noun, hit, the, ball Noun, Verb, the, ball Noun, Verb, Article, ball Noun, Verb, Article, Noun NP, Verb, Article, Noun NP, Verb, NP NP, VP S

12. Definite Clause Grammar (DCG)
Gramatici BNF - probleme
Utilizare LP – clauze Horn definite
Gramatici cu clauze definite (DCG)
Fiecare regula din gramatica poate fi vazuta ca o regula din DCG
Fiecare categorie sintactica se reprezinta printr-un predicat cu un argument sir

13. Definite Clause Grammar (DCG)
NP(s) este adevarat daca s este NP
S  NP VP devine
NP(s1)  VP(s2)  S(append(s1,s2))
Analiza (parsing) = inferenta logica
Bottom-up parsing – foreward chaining
Top-down parsing – backward chaining
Aceeasi gramatica utilizata atat pentru analiza cat si pentru generare

14. Reguli de corespondenta
In BNF S  NP VP In LP / DGC NP(s1)  VP(s2)  S(append(s1, s2)) In BNF NP  Pronoun | Noun In LP / DGC Pronoun(s)  Noun(s)  NP(s) BNF Noun  ball | book In LP / DGC (s = “ball”  s = “book”)  Noun(s)
Reguli de corespondenta

15. BNF, DCG, Prolog BNF FOPL/DCG PROLOG 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)
(s = “stench”  s = “wumpus”) 
Noun(s)
Verb(s)  VP(s)
(v = “smells”  v = “kills”) 
Verb(v)
sentence([S1, S2]) :-
np(S1), vp(S2).
np(S):- noun(S).
noun(stench).
noun(wumpus).
vp(S):- verb(S).
verb(smells).
verb(kills).
?- sentence([wumpus, smells]).
?-sentence([S1, S2]).

16. Imbogatire DCG Imbogatesc neterminale cu argumente suplimentare
Rol argumente:
Ataseseaza semantica
Verifica corectitudinea gramaticala
Adauga expresii / functii care se testeaza

17. Argument pt semantica BNF FOPL/DCG semantica compozitionala
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

18. 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,minge).
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]
?- sentence([is,dog,bytes],Sem). No
?- sentence([the,dog,has,legs],Sem).
Sem = [caine, parti, picioare]

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

20. Cazuri S  NP(Nominativ) VP
Nominativ (subjective)
I take the bus Eu iau autobuzul
You take the bus Tu iei autobuzul
He takes the bus El ia autobuzul
Acuzativ (objective)
He gives me the book Imi da cartea
S  NP(Nominativ) VP
NP(case)  Pronoun (case) | Noun | Article Noun
// I
VP  VP NP(Acuzativ) // believe him
VP  VP PP // turn to the right
VP  VP Adjective
VP  Verb
PP  Preposition NP(Acuzativ)
Pronoun(Nominativ)  I | you | he | she
Pronoun(Acuzativ)  me | you | him | her

21. sentence(S) :- np(S1,nominativ), vp(S2), append(S1, S2, S)
sentence(S) :- np(S1,nominativ), 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, nominativ). pronoun(you, _ ). pronoun(he, nominativ). pronoun(she, nominativ). pronoun(me, acuzativ). pronoun(him, acuzativ). pronoun(her, acuzativ). noun(ball). noun(stick). article(a). article(the).

22. Subcategorii verbe S  NP(Nominativ) VP(subcat)
Lista de subcategorii: ce complemente accepta verbul
depinde de verb
S  NP(Nominativ) VP(subcat)
VP(subcat)  VP(subcat) PP
| VP(subcat) Adverb
I smell the wumpus now

23. VP(subcat)  {subcat = np} VP(np) NP(Acuzativ)
VP(subcat)  {subcat = np} VP(np) NP(Acuzativ) | {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

24. Cazuri si subcategorii
S  NP(Nominativ) VP(subcat) NP(case)  Pronoun (case) | Noun | Article Noun Pronoun(Nominativ)  I | you | he | she Pronoun(Acuzativ)  me | you | him | her VP(subcat)  {subcat = np} VP(np) NP(Acuzativ) | {subcat = adj} VP(adj) Adjective | {subcat = pp} VP (pp) PP | Verb | VP(subcat) PP | VP(subcat) Adverb

25. VP(subcat)  {subcat = np} VP(np) NP(Acuzativ)
VP(subcat)  {subcat = np} VP(np) NP(Acuzativ) | {subcat = adj} VP(adj) Adjective | {subcat = pp} VP (pp) PP | Verb | VP(subcat) PP | VP(subcat) Adverb sentence(S) :- np(S1,nominativ), vp(S2, Subcat), append(S1, S2, S). VP(Subcat)  VP(Subcat) … !!! vp(S, Subcat) :- Subcat = np, vp1(S1, np),np(S2, acuzativ), 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).

26. Analiza pragmatica Analiza semantica Eliminare ambiguitate
Interpretare pragmatica
Mod de utilizare si efect asupra receptorului;
Completeaza interpretarea semantica prin considerarea informatiilor despre situatia curenta
Indexical – refera situatia curenta
Anafora – refera obiecte deja mentionate

27. Ambiguitate Lexicala – acelasi cuvant diverse intelesuri
Sintactica – arbori diferiti de analiza
Referentiala – referire la obiecte anterioare
Pragmatica – referire la loc, timp