An Experiment using Term

Extended Abstract Introduction The purpose of this extended abstract is to report on a preliminary investigation into the use of term rewriting theorem proving to support veriication of formal description techniques for concurrent systems. The RRL 1, 2] system, particularly Knuth-Bendix completion and equational proofs, is used to investigate veriication of speciications written in the formal description language LOTOS. This work was completed as part of the SERC/IED ERIL project, which is investigating the use of Equational Reasoning for LOTOS. A more complete presentation of the results given here may be found in 3]. That paper also reports on complementary work, also undertaken as part of the ERIL project, using the LP theorem prover 4] for equational and inductive proofs about CSP 5]. The examples we present are all small ones, but are already at the level where hand veriication is tedious and error prone. They execute immediately in RRL, and give hope that the same techniques can be used on much larger examples. LOTOS (Language of Temporal Ordering Speciication) is based on the concept of specifying a system in terms of observable behaviour, i.e. events. Constraints may be expressed on the order of events, but there is no explicit representation of time. The communication and change of information within a system is expressed by the structure of the events. LOTOS is made up of two distinct parts. The process part describes the behaviour of processes and is based on CCS, with some modiications drawn from other concurrency formalisms, such as CSP. The abstract data type part describes the observable behaviour of the data being exchanged by the processes. The application of term rewriting systems to abstract data types is a well researched area; Funded by SERC grant gr/f 35371/ 4/1/1477, Veriication Techniques for LOTOS.