More recently, Gislason and Craig have extended and
generalized the original version of the global formulation as
follows. A thermodynamic event involves various subsystems or
parts, any one of which can be called the system. The totality of
the parts is the “universe of the event”, which for the sake of
brevity in this article will be called the supersystem. No matter or
energy is transferred into or out of the supersystem. In what
follows, the supersystem is indicated by subscript “ss”, the
system is indicated by subscript “sys”, and index i is used to
label the parts of the system's surroundings within the
supersystem.