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Inteligenta Artificiala

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Title: Natural Language Processing Author: serban Last modified by: Adina Magda Florea Created Date: 5/8/2004 3:17:36 PM Document presentation format – PowerPoint PPT presentation

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Title: Inteligenta Artificiala


1
Inteligenta Artificiala
  • Universitatea Politehnica BucurestiAnul
    universitar 2008-2009
  • Adina Florea
  • http//turing.cs.pub.ro/ia_08 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
  • 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
LexiconNoun ? 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
7
Gramatica
  • Neterminale diferite categorii din propozitie
  • sentence S
  • noun phrase NP
  • verb phrase VP
  • prepositional phrase PP
  • relative clause RelClause

8
ExempluS ? 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
9
Analiza sintactica
  • top-down parsing
  • bottom-up parsing

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)
  • 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
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) BNFNoun ? 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
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 Yes ?- sentence(is,dog,bytes,Se
m). No ?- sentence(the,dog,has,legs,Sem). Sem
caine, parti, picioare Yes
19
Verificare corectitudine gramaticala
  • cazuri
  • subcategorii verbe complementul pe care il poate
    accepta un verb
  • acord subiect predicat
  • etc.
  • Parametrizarea neterminalelor

20
  • Cazuri
  • 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).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).ar
ticle(the).
22
Subcategorii verbe
  • 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) subcat adj VP(adj)
Adjective subcat pp VP (pp) PP
Verb smell NP smell a wumpus Adjective sme
ll awfull PP smell like a wumpusis Adjectiv
e is smelly PP is in box NP is a
pitgive NP, PP give the gold in box to
me NP, NP give me the golddied died
24
S ? NP(Nominativ) VP(subcat)NP(case) ?
Pronoun (case) Noun Article
NounPronoun(Nominativ) ? I you he
shePronoun(Acuzativ) ? me you him
herVP(subcat) ? subcat np VP(np)
NP(Acuzativ) subcat adj VP(adj)
Adjective subcat pp VP (pp) PP
Verb VP(subcat) PP VP(subcat) Adverb
Cazuri si subcategorii
25
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(giv
e).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
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