Historically, these start with the IBM system,
which was used to specify large parts of the Systems Network
Architecture. It is an extension of PL/1,
to include Finite State Machines
(FSM) and state transition.
RSPL was developed at the technical University in Berlin to specify
protocol sequences and alternate actions.
ISO formed two committees to work in this area, and the two
draft proposals for systems are:
LOTOS is based on some firm mathematics in Temporal Logic, that
allows the proof of behavior of the processes described.
ESTL or Extended State Transition Language (;SPM_quot;Estelle;SPM_quot;), which is an
extended FSM approach, based on ISO standard Pascal.
LOTOS or the Language of Temporal Ordering Specification, derived
from The Calculus of Communicating Systems
and related to Communicating Sequential Processes