PARTIAL ORDER MODELS FOR QUANTITATIVE EXTENSIONS OF LOTOS

Event structures are a prominent model for non-interleaving concurrenc y. The use of event structures for providing a compositional non-inter leaving semantics to LOTOS without data is studied. In particular, sev eral quantitative extensions of event structures are proposed that inc orporate notions like time - both of deterministic and stochastic natu re - and probability. The suitability of these models for giving a non -interleaving semantics to a timed, stochastic and probabilistic exten sion of LOTOS is investigated. Consistency between the event structure semantics and an (event-based) operational semantics is addressed for the different quantitative variants of LOTOS and is worked out for th e timed case in more detail. These consistency results facilitate the coherent use of an interleaving and a non-interleaving semantic view i n a single design trajectory and provide a justification for the event structure semantics. As a running example an infinite buffer is used in which gradually timing constraints on latency and rates of acceptin g and producing data and the probability of loss of messages are incor porated. (C) 1998 Elsevier Science B.V. All rights reserved.