def backward_chaining(kb, query):
all_variables = find_variables_symbol(query)
query, var_map = standardize_variables(query)
result = __backward_chaining_or(kb, query, {})
if result is not problem.FAILURE:
propagate_substitutions(result)
query_vars = {var: result[var_map[var]] for var in all_variables}
return query_vars
return result
def backward_chaining(kb, query):
all_variables = find_variables_symbol(query)
query, var_map = standardize_variables(query)
result = __backward_chaining_or(kb, query, {})
if result is not problem.FAILURE:
propagate_substitutions(result)
query_vars = {var: result[var_map[var]] for var in all_variables}
return query_vars
return result
def __resolution_step(new_inferrences, already_resolved,
clauses, max_clause_len,
clause_mapping, empty_set=frozenset()):
new_inferrences.clear()
pairs = ((clauses[i], clauses[j])
for i in range(len(clauses))
for j in range(i + 1, len(clauses))
if (clauses[i], clauses[j]) not in already_resolved)
for c1, c2 in pairs:
resolvents = __resolve(c1, c2, max_clause_len, clause_mapping)
if empty_set in resolvents:
bindings = clause_mapping.container[empty_set][0]
bindings = propagate_substitutions(bindings)
return True, bindings
new_inferrences.update(resolvents)
already_resolved.add((c1, c2))
if new_inferrences.issubset(clauses):
return False, {}
clauses.extend(clause for clause in new_inferrences
if not is_subsumed_in(clause, clauses))
return None
def __resolution_step(new_inferrences,
already_resolved,
clauses,
max_clause_len,
clause_mapping,
empty_set=frozenset()):
new_inferrences.clear()
pairs = ((clauses[i], clauses[j]) for i in range(len(clauses))
for j in range(i + 1, len(clauses))
if (clauses[i], clauses[j]) not in already_resolved)
for c1, c2 in pairs:
resolvents = __resolve(c1, c2, max_clause_len, clause_mapping)
if empty_set in resolvents:
bindings = clause_mapping.container[empty_set][0]
bindings = propagate_substitutions(bindings)
return True, bindings
new_inferrences.update(resolvents)
already_resolved.add((c1, c2))
if new_inferrences.issubset(clauses):
return False, {}
clauses.extend(clause for clause in new_inferrences
if not is_subsumed_in(clause, clauses))
return None
