LOTOS is a Formal Description Technique (FDT) standardized by ISO for the design of distributed systems, and in particular for OSI services and protocols. Experts of the ISO FDT group developed LOTOS from 1981 to 1988; it has now the status of International Standard (ISO 8807:1989).
Unlike FDTs based on the state representation of a system, LOTOS describes a system by defining the temporal relations between externally observable events at so-called event gates.
LOTOS is composed of two parts : a process algebraic part based on
Milner's Calculus of Communicating Systems (CCS) and on Hoare's Communicating Sequential Processes (CSP), and a data algebraic part
based on the abstract data type language (ACT ONE). These two aspects of LOTOS are complementary and independent : the process
algebra is used to model dynamic behaviours of systems, and ACT ONE is used to model data structures and value expressions.
LOTOS has been widely used for the specification of large data communication systems. It is mathematically well-defined and expressive: it
allows the description of concurrency, nondeterminism, synchronous and asynchronous communications. It supports various levels of
abstraction and provides several specification styles. Good tools (e.g. the EUCALYPTUS toolset) exist to support specification, verification
and code generation. Finally, LOTOS is one of the few process algebras to have moved out of the theoretical community.
Back to the CADP Home Page