Steady state thermodynamics

A phenomenological framework corresponding to equilibrium thermodynamics is constructed for steady states. All the key concepts including entropy are operationally defined. If a system is strictly linear, the resultant Gibbs relation justifies the postulated form in the extended irreversible thermodynamics. The resultant Maxwell's relations and stability criteria give various le Chatelier-Braun type qualitative predictions. A phenomenological fluctuation theory around steady states is also formulated.