Source code for nltk.sem.glue

# Natural Language Toolkit: Glue Semantics
#
# Author: Dan Garrette <dhgarrette@gmail.com>
#
# Copyright (C) 2001-2017 NLTK Project
# URL: <http://nltk.org/>
# For license information, see LICENSE.TXT
from __future__ import print_function, division, unicode_literals

import os
from itertools import chain

from six import string_types

import nltk
from nltk.internals import Counter
from nltk.tag import UnigramTagger, BigramTagger, TrigramTagger, RegexpTagger
from nltk.sem.logic import (Expression, Variable, VariableExpression,
                            LambdaExpression, AbstractVariableExpression)
from nltk.compat import python_2_unicode_compatible
from nltk.sem import drt
from nltk.sem import linearlogic

SPEC_SEMTYPES = {'a'       : 'ex_quant',
                 'an'      : 'ex_quant',
                 'every'   : 'univ_quant',
                 'the'     : 'def_art',
                 'no'      : 'no_quant',
                 'default' : 'ex_quant'}

OPTIONAL_RELATIONSHIPS = ['nmod', 'vmod', 'punct']

@python_2_unicode_compatible
[docs]class GlueFormula(object): def __init__(self, meaning, glue, indices=None): if not indices: indices = set() if isinstance(meaning, string_types): self.meaning = Expression.fromstring(meaning) elif isinstance(meaning, Expression): self.meaning = meaning else: raise RuntimeError('Meaning term neither string or expression: %s, %s' % (meaning, meaning.__class__)) if isinstance(glue, string_types): self.glue = linearlogic.LinearLogicParser().parse(glue) elif isinstance(glue, linearlogic.Expression): self.glue = glue else: raise RuntimeError('Glue term neither string or expression: %s, %s' % (glue, glue.__class__)) self.indices = indices
[docs] def applyto(self, arg): """ self = (\\x.(walk x), (subj -o f)) arg = (john , subj) returns ((walk john), f) """ if self.indices & arg.indices: # if the sets are NOT disjoint raise linearlogic.LinearLogicApplicationException("'%s' applied to '%s'. Indices are not disjoint." % (self, arg)) else: # if the sets ARE disjoint return_indices = (self.indices | arg.indices) try: return_glue = linearlogic.ApplicationExpression(self.glue, arg.glue, arg.indices) except linearlogic.LinearLogicApplicationException: raise linearlogic.LinearLogicApplicationException("'%s' applied to '%s'" % (self.simplify(), arg.simplify())) arg_meaning_abstracted = arg.meaning if return_indices: for dep in self.glue.simplify().antecedent.dependencies[::-1]: # if self.glue is (A -o B), dep is in A.dependencies arg_meaning_abstracted = self.make_LambdaExpression(Variable('v%s' % dep), arg_meaning_abstracted) return_meaning = self.meaning.applyto(arg_meaning_abstracted) return self.__class__(return_meaning, return_glue, return_indices)
[docs] def make_VariableExpression(self, name): return VariableExpression(name)
[docs] def make_LambdaExpression(self, variable, term): return LambdaExpression(variable, term)
[docs] def lambda_abstract(self, other): assert isinstance(other, GlueFormula) assert isinstance(other.meaning, AbstractVariableExpression) return self.__class__(self.make_LambdaExpression(other.meaning.variable, self.meaning), linearlogic.ImpExpression(other.glue, self.glue))
[docs] def compile(self, counter=None): """From Iddo Lev's PhD Dissertation p108-109""" if not counter: counter = Counter() (compiled_glue, new_forms) = self.glue.simplify().compile_pos(counter, self.__class__) return new_forms + [self.__class__(self.meaning, compiled_glue, set([counter.get()]))]
[docs] def simplify(self): return self.__class__(self.meaning.simplify(), self.glue.simplify(), self.indices)
def __eq__(self, other): return self.__class__ == other.__class__ and self.meaning == other.meaning and self.glue == other.glue def __ne__(self, other): return not self == other # sorting for use in doctests which must be deterministic def __lt__(self, other): return str(self) < str(other) def __str__(self): assert isinstance(self.indices, set) accum = '%s : %s' % (self.meaning, self.glue) if self.indices: accum += ' : {' + ', '.join(str(index) for index in self.indices) + '}' return accum def __repr__(self): return "%s" % self
@python_2_unicode_compatible
[docs]class GlueDict(dict): def __init__(self, filename, encoding=None): self.filename = filename self.file_encoding = encoding self.read_file()
[docs] def read_file(self, empty_first=True): if empty_first: self.clear() try: contents = nltk.data.load(self.filename, format='text', encoding=self.file_encoding) # TODO: the above can't handle zip files, but this should anyway be fixed in nltk.data.load() except LookupError as e: try: contents = nltk.data.load('file:' + self.filename, format='text', encoding=self.file_encoding) except LookupError: raise e lines = contents.splitlines() for line in lines: # example: 'n : (\\x.(<word> x), (v-or))' # lambdacalc -^ linear logic -^ line = line.strip() # remove trailing newline if not len(line): continue # skip empty lines if line[0] == '#': continue # skip commented out lines parts = line.split(' : ', 2) # ['verb', '(\\x.(<word> x), ( subj -o f ))', '[subj]'] glue_formulas = [] paren_count = 0 tuple_start = 0 tuple_comma = 0 relationships = None if len(parts) > 1: for (i, c) in enumerate(parts[1]): if c == '(': if paren_count == 0: # if it's the first '(' of a tuple tuple_start = i+1 # then save the index paren_count += 1 elif c == ')': paren_count -= 1 if paren_count == 0: # if it's the last ')' of a tuple meaning_term = parts[1][tuple_start:tuple_comma] # '\\x.(<word> x)' glue_term = parts[1][tuple_comma+1:i] # '(v-r)' glue_formulas.append([meaning_term, glue_term]) # add the GlueFormula to the list elif c == ',': if paren_count == 1: # if it's a comma separating the parts of the tuple tuple_comma = i # then save the index elif c == '#': # skip comments at the ends of lines if paren_count != 0: # if the line hasn't parsed correctly so far raise RuntimeError('Formula syntax is incorrect for entry ' + line) break # break to the next line if len(parts) > 2: #if there is a relationship entry at the end rel_start = parts[2].index('[')+1 rel_end = parts[2].index(']') if rel_start == rel_end: relationships = frozenset() else: relationships = frozenset(r.strip() for r in parts[2][rel_start:rel_end].split(',')) try: start_inheritance = parts[0].index('(') end_inheritance = parts[0].index(')') sem = parts[0][:start_inheritance].strip() supertype = parts[0][start_inheritance+1:end_inheritance] except: sem = parts[0].strip() supertype = None if sem not in self: self[sem] = {} if relationships is None: #if not specified for a specific relationship set #add all relationship entries for parents if supertype: for rels in self[supertype]: if rels not in self[sem]: self[sem][rels] = [] glue = self[supertype][rels] self[sem][rels].extend(glue) self[sem][rels].extend(glue_formulas) # add the glue formulas to every rel entry else: if None not in self[sem]: self[sem][None] = [] self[sem][None].extend(glue_formulas) # add the glue formulas to every rel entry else: if relationships not in self[sem]: self[sem][relationships] = [] if supertype: self[sem][relationships].extend(self[supertype][relationships]) self[sem][relationships].extend(glue_formulas) # add the glue entry to the dictionary
def __str__(self): accum = '' for pos in self: str_pos = "%s" % pos for relset in self[pos]: i = 1 for gf in self[pos][relset]: if i == 1: accum += str_pos + ': ' else: accum += ' '*(len(str_pos)+2) accum += "%s" % gf if relset and i == len(self[pos][relset]): accum += ' : %s' % relset accum += '\n' i += 1 return accum
[docs] def to_glueformula_list(self, depgraph, node=None, counter=None, verbose=False): if node is None: # TODO: should it be depgraph.root? Is this code tested? top = depgraph.nodes[0] depList = list(chain(*top['deps'].values())) root = depgraph.nodes[depList[0]] return self.to_glueformula_list(depgraph, root, Counter(), verbose) glueformulas = self.lookup(node, depgraph, counter) for dep_idx in chain(*node['deps'].values()): dep = depgraph.nodes[dep_idx] glueformulas.extend(self.to_glueformula_list(depgraph, dep, counter, verbose)) return glueformulas
[docs] def lookup(self, node, depgraph, counter): semtype_names = self.get_semtypes(node) semtype = None for name in semtype_names: if name in self: semtype = self[name] break if semtype is None: # raise KeyError, "There is no GlueDict entry for sem type '%s' (for '%s')" % (sem, word) return [] self.add_missing_dependencies(node, depgraph) lookup = self._lookup_semtype_option(semtype, node, depgraph) if not len(lookup): raise KeyError( "There is no GlueDict entry for sem type of '%s' " "with tag '%s', and rel '%s'" % (node['word'], node['tag'], node['rel']) ) return self.get_glueformulas_from_semtype_entry(lookup, node['word'], node, depgraph, counter)
[docs] def add_missing_dependencies(self, node, depgraph): rel = node['rel'].lower() if rel == 'main': headnode = depgraph.nodes[node['head']] subj = self.lookup_unique('subj', headnode, depgraph) relation = subj['rel'] node['deps'].setdefault(relation,[]) node['deps'][relation].append(subj['address'])
#node['deps'].append(subj['address']) def _lookup_semtype_option(self, semtype, node, depgraph): relationships = frozenset( depgraph.nodes[dep]['rel'].lower() for dep in chain(*node['deps'].values()) if depgraph.nodes[dep]['rel'].lower() not in OPTIONAL_RELATIONSHIPS ) try: lookup = semtype[relationships] except KeyError: # An exact match is not found, so find the best match where # 'best' is defined as the glue entry whose relationship set has the # most relations of any possible relationship set that is a subset # of the actual depgraph best_match = frozenset() for relset_option in set(semtype)-set([None]): if len(relset_option) > len(best_match) and \ relset_option < relationships: best_match = relset_option if not best_match: if None in semtype: best_match = None else: return None lookup = semtype[best_match] return lookup
[docs] def get_semtypes(self, node): """ Based on the node, return a list of plausible semtypes in order of plausibility. """ rel = node['rel'].lower() word = node['word'].lower() if rel == 'spec': if word in SPEC_SEMTYPES: return [SPEC_SEMTYPES[word]] else: return [SPEC_SEMTYPES['default']] elif rel in ['nmod', 'vmod']: return [node['tag'], rel] else: return [node['tag']]
[docs] def get_glueformulas_from_semtype_entry(self, lookup, word, node, depgraph, counter): glueformulas = [] glueFormulaFactory = self.get_GlueFormula_factory() for meaning, glue in lookup: gf = glueFormulaFactory(self.get_meaning_formula(meaning, word), glue) if not len(glueformulas): gf.word = word else: gf.word = '%s%s' % (word, len(glueformulas)+1) gf.glue = self.initialize_labels(gf.glue, node, depgraph, counter.get()) glueformulas.append(gf) return glueformulas
[docs] def get_meaning_formula(self, generic, word): """ :param generic: A meaning formula string containing the parameter "<word>" :param word: The actual word to be replace "<word>" """ word = word.replace('.', '') return generic.replace('<word>', word)
[docs] def initialize_labels(self, expr, node, depgraph, unique_index): if isinstance(expr, linearlogic.AtomicExpression): name = self.find_label_name(expr.name.lower(), node, depgraph, unique_index) if name[0].isupper(): return linearlogic.VariableExpression(name) else: return linearlogic.ConstantExpression(name) else: return linearlogic.ImpExpression( self.initialize_labels(expr.antecedent, node, depgraph, unique_index), self.initialize_labels(expr.consequent, node, depgraph, unique_index) )
[docs] def find_label_name(self, name, node, depgraph, unique_index): try: dot = name.index('.') before_dot = name[:dot] after_dot = name[dot+1:] if before_dot == 'super': return self.find_label_name(after_dot, depgraph.nodes[node['head']], depgraph, unique_index) else: return self.find_label_name(after_dot, self.lookup_unique(before_dot, node, depgraph), depgraph, unique_index) except ValueError: lbl = self.get_label(node) if name == 'f': return lbl elif name == 'v': return '%sv' % lbl elif name == 'r': return '%sr' % lbl elif name == 'super': return self.get_label(depgraph.nodes[node['head']]) elif name == 'var': return '%s%s' % (lbl.upper(), unique_index) elif name == 'a': return self.get_label(self.lookup_unique('conja', node, depgraph)) elif name == 'b': return self.get_label(self.lookup_unique('conjb', node, depgraph)) else: return self.get_label(self.lookup_unique(name, node, depgraph))
[docs] def get_label(self, node): """ Pick an alphabetic character as identifier for an entity in the model. :param value: where to index into the list of characters :type value: int """ value = node['address'] letter = ['f','g','h','i','j','k','l','m','n','o','p','q','r','s', 't','u','v','w','x','y','z','a','b','c','d','e'][value-1] num = int(value) // 26 if num > 0: return letter + str(num) else: return letter
[docs] def lookup_unique(self, rel, node, depgraph): """ Lookup 'key'. There should be exactly one item in the associated relation. """ deps = [ depgraph.nodes[dep] for dep in chain(*node['deps'].values()) if depgraph.nodes[dep]['rel'].lower() == rel.lower() ] if len(deps) == 0: raise KeyError("'%s' doesn't contain a feature '%s'" % (node['word'], rel)) elif len(deps) > 1: raise KeyError("'%s' should only have one feature '%s'" % (node['word'], rel)) else: return deps[0]
[docs] def get_GlueFormula_factory(self): return GlueFormula
[docs]class Glue(object): def __init__(self, semtype_file=None, remove_duplicates=False, depparser=None, verbose=False): self.verbose = verbose self.remove_duplicates = remove_duplicates self.depparser = depparser from nltk import Prover9 self.prover = Prover9() if semtype_file: self.semtype_file = semtype_file else: self.semtype_file = os.path.join('grammars', 'sample_grammars','glue.semtype')
[docs] def train_depparser(self, depgraphs=None): if depgraphs: self.depparser.train(depgraphs) else: self.depparser.train_from_file(nltk.data.find( os.path.join('grammars', 'sample_grammars', 'glue_train.conll')))
[docs] def parse_to_meaning(self, sentence): readings = [] for agenda in self.parse_to_compiled(sentence): readings.extend(self.get_readings(agenda)) return readings
[docs] def get_readings(self, agenda): readings = [] agenda_length = len(agenda) atomics = dict() nonatomics = dict() while agenda: # is not empty cur = agenda.pop() glue_simp = cur.glue.simplify() if isinstance(glue_simp, linearlogic.ImpExpression): # if cur.glue is non-atomic for key in atomics: try: if isinstance(cur.glue, linearlogic.ApplicationExpression): bindings = cur.glue.bindings else: bindings = linearlogic.BindingDict() glue_simp.antecedent.unify(key, bindings) for atomic in atomics[key]: if not (cur.indices & atomic.indices): # if the sets of indices are disjoint try: agenda.append(cur.applyto(atomic)) except linearlogic.LinearLogicApplicationException: pass except linearlogic.UnificationException: pass try: nonatomics[glue_simp.antecedent].append(cur) except KeyError: nonatomics[glue_simp.antecedent] = [cur] else: # else cur.glue is atomic for key in nonatomics: for nonatomic in nonatomics[key]: try: if isinstance(nonatomic.glue, linearlogic.ApplicationExpression): bindings = nonatomic.glue.bindings else: bindings = linearlogic.BindingDict() glue_simp.unify(key, bindings) if not (cur.indices & nonatomic.indices): # if the sets of indices are disjoint try: agenda.append(nonatomic.applyto(cur)) except linearlogic.LinearLogicApplicationException: pass except linearlogic.UnificationException: pass try: atomics[glue_simp].append(cur) except KeyError: atomics[glue_simp] = [cur] for entry in atomics: for gf in atomics[entry]: if len(gf.indices) == agenda_length: self._add_to_reading_list(gf, readings) for entry in nonatomics: for gf in nonatomics[entry]: if len(gf.indices) == agenda_length: self._add_to_reading_list(gf, readings) return readings
def _add_to_reading_list(self, glueformula, reading_list): add_reading = True if self.remove_duplicates: for reading in reading_list: try: if reading.equiv(glueformula.meaning, self.prover): add_reading = False break except Exception as e: #if there is an exception, the syntax of the formula #may not be understandable by the prover, so don't #throw out the reading. print('Error when checking logical equality of statements', e) pass if add_reading: reading_list.append(glueformula.meaning)
[docs] def parse_to_compiled(self, sentence): gfls = [self.depgraph_to_glue(dg) for dg in self.dep_parse(sentence)] return [self.gfl_to_compiled(gfl) for gfl in gfls]
[docs] def dep_parse(self, sentence): """ Return a dependency graph for the sentence. :param sentence: the sentence to be parsed :type sentence: list(str) :rtype: DependencyGraph """ #Lazy-initialize the depparser if self.depparser is None: from nltk.parse import MaltParser self.depparser = MaltParser(tagger=self.get_pos_tagger()) if not self.depparser._trained: self.train_depparser() return self.depparser.parse(sentence, verbose=self.verbose)
[docs] def depgraph_to_glue(self, depgraph): return self.get_glue_dict().to_glueformula_list(depgraph)
[docs] def get_glue_dict(self): return GlueDict(self.semtype_file)
[docs] def gfl_to_compiled(self, gfl): index_counter = Counter() return_list = [] for gf in gfl: return_list.extend(gf.compile(index_counter)) if self.verbose: print('Compiled Glue Premises:') for cgf in return_list: print(cgf) return return_list
[docs] def get_pos_tagger(self): from nltk.corpus import brown regexp_tagger = RegexpTagger( [(r'^-?[0-9]+(.[0-9]+)?$', 'CD'), # cardinal numbers (r'(The|the|A|a|An|an)$', 'AT'), # articles (r'.*able$', 'JJ'), # adjectives (r'.*ness$', 'NN'), # nouns formed from adjectives (r'.*ly$', 'RB'), # adverbs (r'.*s$', 'NNS'), # plural nouns (r'.*ing$', 'VBG'), # gerunds (r'.*ed$', 'VBD'), # past tense verbs (r'.*', 'NN') # nouns (default) ]) brown_train = brown.tagged_sents(categories='news') unigram_tagger = UnigramTagger(brown_train, backoff=regexp_tagger) bigram_tagger = BigramTagger(brown_train, backoff=unigram_tagger) trigram_tagger = TrigramTagger(brown_train, backoff=bigram_tagger) #Override particular words main_tagger = RegexpTagger( [(r'(A|a|An|an)$', 'ex_quant'), (r'(Every|every|All|all)$', 'univ_quant') ], backoff=trigram_tagger) return main_tagger
[docs]class DrtGlueFormula(GlueFormula): def __init__(self, meaning, glue, indices=None): if not indices: indices = set() if isinstance(meaning, string_types): self.meaning = drt.DrtExpression.fromstring(meaning) elif isinstance(meaning, drt.DrtExpression): self.meaning = meaning else: raise RuntimeError('Meaning term neither string or expression: %s, %s' % (meaning, meaning.__class__)) if isinstance(glue, string_types): self.glue = linearlogic.LinearLogicParser().parse(glue) elif isinstance(glue, linearlogic.Expression): self.glue = glue else: raise RuntimeError('Glue term neither string or expression: %s, %s' % (glue, glue.__class__)) self.indices = indices
[docs] def make_VariableExpression(self, name): return drt.DrtVariableExpression(name)
[docs] def make_LambdaExpression(self, variable, term): return drt.DrtLambdaExpression(variable, term)
[docs]class DrtGlueDict(GlueDict):
[docs] def get_GlueFormula_factory(self): return DrtGlueFormula
[docs]class DrtGlue(Glue): def __init__(self, semtype_file=None, remove_duplicates=False, depparser=None, verbose=False): if not semtype_file: semtype_file = os.path.join('grammars', 'sample_grammars','drt_glue.semtype') Glue.__init__(self, semtype_file, remove_duplicates, depparser, verbose)
[docs] def get_glue_dict(self): return DrtGlueDict(self.semtype_file)
[docs]def demo(show_example=-1): from nltk.parse import MaltParser examples = ['David sees Mary', 'David eats a sandwich', 'every man chases a dog', 'every man believes a dog sleeps', 'John gives David a sandwich', 'John chases himself'] # 'John persuades David to order a pizza', # 'John tries to go', # 'John tries to find a unicorn', # 'John seems to vanish', # 'a unicorn seems to approach', # 'every big cat leaves', # 'every gray cat leaves', # 'every big gray cat leaves', # 'a former senator leaves', print('============== DEMO ==============') tagger = RegexpTagger( [('^(David|Mary|John)$', 'NNP'), ('^(sees|eats|chases|believes|gives|sleeps|chases|persuades|tries|seems|leaves)$', 'VB'), ('^(go|order|vanish|find|approach)$', 'VB'), ('^(a)$', 'ex_quant'), ('^(every)$', 'univ_quant'), ('^(sandwich|man|dog|pizza|unicorn|cat|senator)$', 'NN'), ('^(big|gray|former)$', 'JJ'), ('^(him|himself)$', 'PRP') ]) depparser = MaltParser(tagger=tagger) glue = Glue(depparser=depparser, verbose=False) for (i, sentence) in enumerate(examples): if i==show_example or show_example==-1: print('[[[Example %s]]] %s' % (i, sentence)) for reading in glue.parse_to_meaning(sentence.split()): print(reading.simplify()) print('')
if __name__ == '__main__': demo()