nltk.sem.hole module

An implementation of the Hole Semantics model, following Blackburn and Bos, Representation and Inference for Natural Language (CSLI, 2005).

The semantic representations are built by the grammar hole.fcfg. This module contains driver code to read in sentences and parse them according to a hole semantics grammar.

After parsing, the semantic representation is in the form of an underspecified representation that is not easy to read. We use a “plugging” algorithm to convert that representation into first-order logic formulas.

class nltk.sem.hole.Constants

Bases: object

ALL = 'ALL'

AND = 'AND'

EXISTS = 'EXISTS'

HOLE = 'HOLE'

IFF = 'IFF'

IMP = 'IMP'

LABEL = 'LABEL'

LEQ = 'LEQ'

MAP = {'ALL': <function Constants.<lambda>>, 'AND': <class 'nltk.sem.logic.AndExpression'>, 'EXISTS': <function Constants.<lambda>>, 'IFF': <class 'nltk.sem.logic.IffExpression'>, 'IMP': <class 'nltk.sem.logic.ImpExpression'>, 'NOT': <class 'nltk.sem.logic.NegatedExpression'>, 'OR': <class 'nltk.sem.logic.OrExpression'>, 'PRED': <class 'nltk.sem.logic.ApplicationExpression'>}

NOT = 'NOT'

OR = 'OR'

PRED = 'PRED'

class nltk.sem.hole.Constraint

Bases: object

This class represents a constraint of the form (L =< N), where L is a label and N is a node (a label or a hole).

__init__(lhs, rhs)

class nltk.sem.hole.HoleSemantics

Bases: object

This class holds the broken-down components of a hole semantics, i.e. it extracts the holes, labels, logic formula fragments and constraints out of a big conjunction of such as produced by the hole semantics grammar. It then provides some operations on the semantics dealing with holes, labels and finding legal ways to plug holes with labels.

__init__(usr)

Constructor. usr’ is a ``sem.Expression` representing an Underspecified Representation Structure (USR). A USR has the following special predicates: ALL(l,v,n), EXISTS(l,v,n), AND(l,n,n), OR(l,n,n), IMP(l,n,n), IFF(l,n,n), PRED(l,v,n,v[,v]*) where the brackets and star indicate zero or more repetitions, LEQ(n,n), HOLE(n), LABEL(n) where l is the label of the node described by the predicate, n is either a label or a hole, and v is a variable.

formula_tree(plugging)

Return the first-order logic formula tree for this underspecified representation using the plugging given.

is_node(x)

Return true if x is a node (label or hole) in this semantic representation.

pluggings()

Calculate and return all the legal pluggings (mappings of labels to holes) of this semantics given the constraints.

nltk.sem.hole.hole_readings(sentence, grammar_filename=None, verbose=False)