def __fetch_implications(kb, query):
implications = []
for implication in kb:
subst = unify(query, implication.conclusion)
if subst != problem.FAILURE:
implication.standardize()
implications.append(implication)
return implications
def is_fo_disjunction_tautology(disjunction):
for symbol in disjunction:
negation = LogicOperator.Negation + symbol
for symbol2 in disjunction:
theta = unify(negation, symbol2)
if theta is not FAILURE:
return True
return False
def __backward_chaining_or(kb, query, theta):
for implication in __fetch_implications(kb, query):
premises, conclusion = implication.premises, implication.conclusion
subst = __backward_chaining_and(kb, premises, unify(query, conclusion, theta))
if subst is not problem.FAILURE:
return subst
return problem.FAILURE
def is_fo_disjunction_tautology(disjunction):
for symbol in disjunction:
negation = LogicOperator.Negation + symbol
for symbol2 in disjunction:
theta = unify(negation, symbol2)
if theta is not FAILURE:
return True
return False
def __fetch_implications(kb, query):
implications = []
for implication in kb:
subst = unify(query, implication.conclusion)
if subst != problem.FAILURE:
implication.standardize()
implications.append(implication)
return implications
def __backward_chaining_or(kb, query, theta):
for implication in __fetch_implications(kb, query):
premises, conclusion = implication.premises, implication.conclusion
subst = __backward_chaining_and(kb, premises,
unify(query, conclusion, theta))
if subst is not problem.FAILURE:
return subst
return problem.FAILURE
def __resolve_single_sided(c1, c2, resolvents, clause_mapping):
for symbol1 in c1:
negation = LogicOperator.Negation + symbol1
for symbol2 in c2:
for th in clause_mapping.get_unified_bindings(c1, c2):
theta = unify(negation, symbol2, th)
if theta is not problem.FAILURE:
result = c1.union(c2).difference({symbol1, symbol2})
resolvent = __standardize_resolvent(result, theta)
resolvents.append(resolvent)
clause_mapping.container[resolvent].append(theta)
def __resolve_single_sided(c1, c2, resolvents, clause_mapping):
for symbol1 in c1:
negation = LogicOperator.Negation + symbol1
for symbol2 in c2:
for th in clause_mapping.get_unified_bindings(c1, c2):
theta = unify(negation, symbol2, th)
if theta is not problem.FAILURE:
result = c1.union(c2).difference({symbol1, symbol2})
resolvent = __standardize_resolvent(result, theta)
resolvents.append(resolvent)
clause_mapping.container[resolvent].append(theta)
def assert_unification(self, first, second, expected, theta={}):
#print(logic.unify(first, second, theta))
self.assertEqual(logic.unify(first, second, theta), expected)
def assert_unification(self, first, second, expected, theta={}):
#print(logic.unify(first, second, theta))
self.assertEqual(logic.unify(first, second, theta), expected)