books.google.at - A model theory that is independent of any concrete logical system allows a general handling of a large variety of logics. This generality can be achieved by applying the theory of institutions that provides a precise mathematical formulation for the intuitive concept of a logical system....http://books.google.at/books/about/Institution_independent_model_theory.html?hl=de&id=aEpn60-EDXwC&q=commutes&utm_source=gb-gplus-shareInstitution-independent model theory
