Milner’s Communication and Concurrency contrasts a notion of “bisimulation” with what he characterizes as the view in standard automata theory. Standard automata theory, however, has a much more interesting and well defined notion of both equivalence and concurrency than what is presented in the process algebra literature. In fact, the absence of any reference to automata products, covering, machine homomorphism, minimization, conversion of NFAs to DFAs, and to Mealy and Moore machines is striking.
Arxiv paper Standard Automata Theory and Process Algebra.
Process algebra and automata theory