Validity
For all sentences Condition, Conclusion, Fact and State_of_affairs,
If Excluded(rule(condition, conclusion), fact, state_of_affairs), Applicable(rule(condition, conclusion), fact, state_of_affairs) or Applies(rule(condition, conclusion), fact, state_of_affairs) is true, then Valid(rule(condition, conclusion)) is true.
A rule can only be excluded, be applicable, or apply if it is valid.