The Complete Axiomatization of Cs-congruence

The coupled simulation equivalence is slightly larger than observation equivalence. Where observation equivalence is based on weak bisimulations, coupled simulation equivalence is based on pairs of simulations which coincide at stable states. We establish the corresponding congruence and provide a complete axiomatization by adding a new-law, :(:P + Q) = :P + Q, to the axioma-tization of observation congruence. We further indicate how the deenition of the equivalence can be extended to divergent transition systems.