Exercise 23.7

Consider the sentence “Someone walked slowly to the supermarket” and a lexicon consisting of the following words:

$Pronoun \rightarrow \textbf{someone} \quad Verb \rightarrow \textbf{walked}$

$Adv \rightarrow \textbf{slowly} \quad Prep \rightarrow \textbf{to}$

$Article \rightarrow \textbf{the} \quad Noun \rightarrow \textbf{supermarket}$

Which of the following three grammars, combined with the lexicon, generates the given sentence? Show the corresponding parse tree(s).

$\quad\quad\quad\quad (A):\quad\quad\quad\quad$ $\quad\quad\quad\quad(B):\quad\quad\quad\quad$ $\quad\quad\quad\quad(C):\quad\quad\quad\quad$
$S\rightarrow NP\space VP$ $S\rightarrow NP\space VP$ $S\rightarrow NP\space VP$
$NP\rightarrow Pronoun$ $NP\rightarrow Pronoun$ $NP\rightarrow Pronoun$
$NP\rightarrow Article\space Noun $ $NP\rightarrow Noun$ $NP\rightarrow Article\space NP$
$VP\rightarrow VP\space PP$ $NP\rightarrow Article\space NP$ $VP\rightarrow Verb\space Adv$
$VP\rightarrow VP\space Adv\space Adv$ $VP\rightarrow Verb\space Vmod$ $Adv\rightarrow Adv\space Adv$
$VP\rightarrow Verb$ $Vmod\rightarrow Adv\space Vmod$ $Adv\rightarrow PP$
$PP\rightarrow Prep\space NP$ $Vmod\rightarrow Adv$ $PP\rightarrow Prep\space NP$
$NP\rightarrow Noun$ $Adv\rightarrow PP$ $NP\rightarrow Noun$
$\quad$ $PP\rightarrow Prep\space NP$ $\quad$

For each of the preceding three grammars, write down three sentences of English and three sentences of non-English generated by the grammar. Each sentence should be significantly different, should be at least six words long, and should include some new lexical entries (which you should define). Suggest ways to improve each grammar to avoid generating the non-English sentences.

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