A Free Energy Foundation of Semantic Similarity in Automata and   Languages
  This paper develops a free energy theory from physics including the variational principles for automata and languages and also provides algorithms to compute the energy as well as efficient algorithms for estimating the nondeterminism in a nondeterministic finite automaton. This theory is then used as a foundation to define a semantic similarity metric for automata and languages. Since automata are a fundamental model for all modern programs while languages are a fundamental model for the programs' behaviors, we believe that the theory and the metric developed in this paper can be further used for real-word programs as well. 
Cewei Cui and Zhe Dang
cs.FL