Can you come up with a feature grammar that can parse the following good
sentences, without parsing any bad ones?
Good:
She has a dog.
She has an animal.
She has some dogs.
She has some animals.
She has some milk.
Bad:
She has an dog.
She has a animal.
She has some dog.
She has a milk.
===================== Grammar ====================
S -> NP VP
NP -> Pronoun
NP -> Det[x] Noun[y]
VP -> Verb NP
x, y satisfy function f(x) = y. Function f is defined as:
f(x) = singular countable noun that begins with a consonant sound if x = 'a'
f(x) = singular countable noun that begins with a vowel sound if x = 'an'
f(x) = plural countable noun OR uncountable noun if x = 'some'
============== Parse Good Sentences ==============
Top down parsing "She has a dog."
S -> NP VP
-> NP(Pronoun) VP(Verb NP)
-> NP(Pronoun(She)) VP(Verb(has) NP(Det Noun))
-> NP(Pronoun(She)) VP(Verb(has) NP(Det(a) Noun(dog)))
x = 'a', y = 'dog' satisfy the grammar.
=> S -> NP(Pronoun(She)) VP(Verb(has) NP(Det(a) Noun(dog)))
S
/ \
NP VP
| / \
| Vert NP
| | / \
| | Det Noun
| | | |
She has a dog
Bottom up parsing "She has some milk."
She <- Pronoun
She <- NP(Pronoun)
has <- Verb
some <- Det
milk <- Noun
x = 'some', y = 'milk' satisfy the grammar, so continue:
some milk <- Det Noun
some milk <- NP(Det Noun)
has some milk <- Verb NP(Det Noun)
S -> NP(Pronoun(She)) VP(Verb(has) NP(Det(some) Noun(milk)))
S
/ \
NP VP
| / \
| Vert NP
| | / \
| | Det Noun
| | | |
She has some milk
============== Parse Bad Sentences ===============
Top down parsing "She has an dog."
S -> NP VP
-> NP(Pronoun) VP(Verb NP)
-> NP(Pronoun(She)) VP(Verb(has) NP(Det Noun))
-> NP(Pronoun(She)) VP(Verb(has) NP(Det(an) Noun(dog)))
x = 'an', y = 'dog' fail the grammar.
=> The given grammar failles to parse "She has an dog"
Bottom up parsing "She has a milk."
She <- Pronoun
She <- NP(Pronoun)
has <- Verb
some <- Det
milk <- Noun
x = 'a', y = 'milk' fail the grammar.
=> The given grammar failles to parse "She has a milk"
