def test_extensionality_contraction(self):
bb = self.belief_base
bb2 = BeliefBase(self.belief_base.beliefs,
selection_function=select_largest_set)
phi = Implication(self.p, self.q)
xi = Or(Not(self.p), self.q)
# Phi is not a member of Belief Base
if entails({}, Biconditional(phi, xi)):
assert False
bb.contract(Belief(phi))
bb2.contract(Belief(xi))
assert bb == bb2
def test_conjunctive_overlap_contraction(self):
bb = self.belief_base
bb2 = BeliefBase(self.belief_base.beliefs,
selection_function=select_largest_set)
bb3 = BeliefBase(self.belief_base.beliefs,
selection_function=select_largest_set)
phi = self.p
xi = self.q
# Phi is not a member of Belief Base
bb.contract(Belief(xi))
bb2.contract(Belief(phi))
bb3.contract(Belief(And(xi, phi)))
assert bb.beliefs.intersection(bb2.beliefs).issubset(bb3.beliefs)
def test_conjunctive_inclusion_contraction(self):
bb = self.belief_base
bb2 = BeliefBase(self.belief_base.beliefs,
selection_function=select_largest_set)
phi = self.p
xi = self.q
# Phi is not a member of Belief Base
bb.contract(Belief(And(phi, xi)))
if entails(bb.get_clauses(), phi):
assert False
bb2.contract(Belief(phi))
assert bb.beliefs.issubset(bb2.beliefs)