title: What is supported in First Order Logics which is not supported in Description Logic?
body: <p>While studying description logics (DL), it is very common to read that it is a fragment of first order logics (FOL), but it is hard to read something explicitely on what is excluded from DL which is part of FOL, which makes DL (with all its dialects ALC, SHOIN etc...) decidable. 
  Or in another words, could you provide me some examples in FOL which are not expressible
  through DL (and which are the reason for semi/non-decidability in FOL) ?</p>