A method to build symbolic representations of LOTOS specifications

Abstract

A symbolic representation of a large state/transition system, based on Binary Decision Diagrams (BDD’s), is generally much more compact than an explicit representation like a Labelled Transition System (LTS). This is due to regular and repetitive patterns occurring in state/transition systems. By exploiting this property, huge state spaces can be represented symbolically, and the resulting BDD representations can be profitably used for activities such as model checking and sequential circuit synthesis. This paper presents a method to build BDD representations from process algebraic specifications, taking LOTOS as a reference. The method exploits the compositionality of process algebras to avoid the enumeration of all the states and transitions. First, small labelled transition systems are created for representing the basic building blocks of the specification. These are converted to BDDs, which in turn are combined together, according to the various process algebraic operators, to obtain the overall BDD. An example is used throughout the paper to illustrate the method.KeywordsProtocol EngineeringLOTOSSymbolic Model CheckingBinary Decision Diagrams.