What is inference? (cont.)

• In plain English: the definition of an Ex-interpretation abstracts the important aspects of that logic family and nothing else

• One can also define equivalence: V ≈ W means W ⊧ V and V ⊧ W

• It is easy to see that {a,A,B|a:A,A ⊑ B} ⊧Ex {a,B|a:B}

• • one has to follow a fairly simple and standard reasoning for sets
  • one can also implement algorithms for general inference checking in Ex