## Natural Language Toolkit: sem0.fcfg
##
## Feature-based grammar that divides the semantics for each element
## into two pieces: the core semantics, with path ('SEM','CORE'), and a set of
## binding operators, with path ('SEM','BO').  Each binding operator is encoded
## as a lambda-calculus expression <bo(expr, @var)>, specifying
## that <@var> is an individual variable that should be instantiated,
## and <expr> is an expression that can bind that variable.
##
## In order for this grammar to generate the correct results, all
## variables of the form <@var> must be instantiated (i.e., replaced
## by unique new variables) whenever they are used.  This can be
## accomplished by using the InstantiateVarsChart class when parsing.
## 
## Author: Edward Loper <edloper@gradient.cis.upenn.edu>,
##         Ewan Klein <ewan@inf.ed.ac.uk> 
## URL: <http://nltk.sourceforge.net>
## For license information, see LICENSE.TXT

%start S
## Grammar summary:
##   S -> NP VP
##   VP -> TV NP | IV
##   NP -> Det N | proper nouns...
##   TV -> transitive verbs...
##   IV -> intransitive verbs...
##   Det -> determiners...

S[SEM=[CORE=<?vp(?subj)>, BO={?b1+?b2}]] -> NP[SEM=[CORE=?subj, BO=?b1]] VP[SEM=[CORE=?vp, BO=?b2]]

VP[SEM=[CORE=<?v(?obj)>, BO={?b1+?b2}]] -> TV[SEM=[CORE=?v, BO=?b1]] NP[SEM=[CORE=?obj, BO=?b2]]

VP[SEM=?s] -> IV[SEM=?s]

NP[SEM=[CORE=<@x>, BO={{<bo(?det(?n), @x)>}+?b1+?b2}]] -> Det[SEM=[CORE=?det, BO=?b1]] N[SEM=[CORE=?n, BO=?b2]]

# Lexical items:
Det[SEM=[CORE=<\Q P.exists x.(Q(x) & P(x))>, BO={/}]] -> 'a'
N[SEM=[CORE=<dog>, BO={/}]] -> 'dog' | 'cat' | 'mouse' 
IV[SEM=[CORE=<\x.bark(x)>, BO={/}]] -> 'barks' | 'eats' | 'walks'
TV[SEM=[CORE=<\x y.feed(y,x)>, BO={/}]] -> 'feeds' | 'walks'
NP[SEM=[CORE=<@x>, BO={<bo(\P. P(John), @x)>}]] -> 'john' | 'alex'