def fol_bc_or(KB, query, theta):
for fact in KB.facts:
fact = fact.get_unit(0)
if fact.checkable(query):
theta_ = unify(fact.get_args(), query.get_args(), theta)
if not theta_ == "Fail":
yield theta_
for rule in KB.rules:
p, q = rule.standardize_apart().get_ante_cons()
if q.checkable(query):
theta_ = unify(q.get_args(), query.get_args(), theta)
for theta1 in fol_bc_and(KB, p, theta_):
yield theta1
def gain_new_knowledge(KB, fact):
for rule in KB.rules:
for idx, unit in enumerate(rule.get_units()):
if unit.potential_conflict(fact):
theta = unify(fact.get_args(), unit.get_args(), {})
if theta == "Fail": continue
remainder = rule.clone()
remainder.remove_unit_at(idx)
remainder = remainder.substitute(theta)
if remainder.get_number_of_units() == 1:
# if not KB.contain_fact(remainder):
KB.add_fact(remainder)
else:
# if not remainder in KB.rules:
KB.add_rule(remainder)
def backward_chain_(KB, goals, theta):
if not goals.to_list():
return [theta]
answers = list()
first, rest = goals.getFirstRest()
q_ = first.substitute(theta)
for rule in KB.rules + KB.facts:
p, q = rule.standardize_apart().get_ante_cons()
if q.checkable(q_):
theta_ = unify(q_.get_args(), q.get_args(), {})
if theta_ == "Fail": continue
new_goals = p
for unit in rest.get_units():
new_goals.add_unit(unit)
compose = compose_theta(theta, theta_)
answers += backward_chain_(KB, new_goals, compose)
return answers
def gain_new_knowledge(KB, clause, query):
for clause_ in KB.rules:
if clause == clause_: continue
for idx, unit in enumerate(clause.get_units()):
for idx_, unit_ in enumerate(clause_.get_units()):
if unit.potential_conflict(unit_):
theta = unify(unit.get_args(), unit_.get_args(), {})
if theta == "Fail": continue
remainder = clause.clone()
remainder_ = clause_.clone()
remainder.remove_unit_at(idx)
remainder_.remove_unit_at(idx_)
for unit in remainder_.get_units():
remainder.add_unit(unit)
if remainder.get_number_of_units() == 0:
yield theta
continue
remainder = remainder.substitute(theta)
KB.add_rule(remainder)
def check_done(new_fact, query):
fact = new_fact.get_unit(0)
if fact.checkable(query):
theta = unify(query.get_args(), fact.get_args(), {})
yield theta
yield "Fail"