Inteligenta Artificiala

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Inteligenta Artificiala

• Universitatea Politehnica BucurestiAnul
  universitar 2008-2009
• Adina Florea
• http//turing.cs.pub.ro/ia_08 si curs.cs.pub.ro

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Curs nr. 13

• Prelucrarea limbajului natural

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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
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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

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Definire 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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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
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Gramatica

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

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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
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Analiza sintactica

• top-down parsing
• bottom-up parsing

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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)

• 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

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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

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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
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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).
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Imbogatire DCG

• Imbogatesc neterminale cu argumente suplimentare
• Rol argumente
• Ataseseaza semantica
• Verifica corectitudinea gramaticala
• Adauga expresii / functii care se testeaza

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Argument pt semantica
semantica compozitionala
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• 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
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Verificare corectitudine gramaticala

• cazuri
• subcategorii verbe complementul pe care il poate
  accepta un verb
• acord subiect predicat
• etc.
• Parametrizarea neterminalelor

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• 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

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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).
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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

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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
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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
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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).
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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

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Ambiguitate

• Lexicala acelasi cuvant diverse intelesuri
• Sintactica arbori diferiti de analiza
• Referentiala referire la obiecte anterioare
• Pragmatica referire la loc, timp