Composition and behaviors of probabilistic I/O automata

We augment the I/O automaton model of Lynch and Tuttle with probability, as a step toward the ultimate goal of obtaining a useful tool for specifying and reasoning about asynchronous probabilistic systems. Our new model, called probabilistic I/O automata, preserves the fundamental properties of the I/O automaton model, such as the asymmetric treatment of input and output and the pleasant notion of asynchronous composition. For certain classes of probabilistic I/O automata, we show that probabilistic behavior maps, which are an abstract representation of I/O automaton behavior in terms of a certain expectation operator, are compositional and fully abstract with respect to a natural notion of probabilistic testing.