def forward_chaining(kb, theorem, verbose=True):
# Salvăm baza de date originală, lucrăm cu o copie
local_kb = deepcopy(kb)
# Două variabile care descriu starea căutării
got_new_facts = True # s-au găsit fapte noi la ultima căutare
is_proved = False # a fost demostrată teorema
# Verificăm dacă teorema este deja demonstrată
for fact in filter(is_fact, local_kb):
if unify(fact, theorem):
if verbose:
print("This already in KB: " + print_formula(fact, True))
is_proved = True
break
while (not is_proved) and got_new_facts:
got_new_facts = False
for rule in filter(is_rule, local_kb):
# Pentru fiecare regulă
new_facts = apply_rule(rule, list(filter(is_fact, local_kb)))
new_facts = list(
filter(
lambda fact: not any(
list(
filter(lambda orig: is_equal_to(fact, orig),
local_kb))), new_facts))
if new_facts:
if verbose:
print("Applied rule: " + print_formula(rule, True) +
", obtained " + str(len(new_facts)) + " new facts.")
if any(filter(lambda t: is_variable(t), get_args(get_conclusion(rule)))) and \
any(filter(lambda fact: is_equal_to(fact, get_conclusion(rule)), new_facts)):
print(
"Demonstration is too general, the conclusion is not instantiated (facts obtained:",
",".join([print_formula(f, True)
for f in new_facts]), ").")
return False
got_new_facts = True
for fact in new_facts:
#if verbose: print("New fact: " + print_formula(fact, True))
if unify(fact, theorem) != False:
is_proved = True
add_statement(local_kb, fact)
if verbose:
print("Now in KB: " + print_formula(fact, True))
break
add_statement(local_kb, fact)
if is_proved:
break
if verbose:
if is_proved:
print("The theorem is TRUE!")
else:
print("The theorem is FALSE!")
return is_proved
def print_state(stare): for atom in stare: print_formula(atom)
def is_fact(formula):
return is_positive_literal(formula)
def is_rule(formula):
return get_head(formula) == 'or' or get_head(formula) == 'and'
# Test!
# formula: P(x) ^ Q(x) -> R(x)
f = make_or(make_neg(make_atom("P", make_var("x"))),
make_neg(make_atom("Q", make_var("x"))),
make_atom("R", make_var("x")))
print(" ; ".join([print_formula(p, True)
for p in get_premises(f)])) # Should be P(?x) ; Q(?x)
print_formula(get_conclusion(f)) # Should be R(?x)
print(is_rule(f)) # must be True
print(is_fact(f)) # must be False
print(is_fact(get_conclusion(f))) # must be True
print(is_rule(get_conclusion(f))) # must be False
def equal_terms(t1, t2):
if is_constant(t1) and is_constant(t2):
return get_value(t1) == get_value(t2)
if is_variable(t1) and is_variable(t2):
return get_name(t1) == get_name(t2)
if is_function_call(t1) and is_function(t2):
if get_head(t1) != get_head(t2):