A true concurrency semantics for ET-LOTOS

One of the central objectives of the LOTOS restandardisation activity is to define an enhanced LOTOS language which supports real-time specification. The timed extension is based upon a timed LOTOS proposal called ET-LOTOS (Enhanced Timed LOTOS). This paper defines a (branching-time) non-interleaving semantics for ET-LOTOS without data. As a denotational model, a suitable timed extension of R. Langerak's (1992, 1993) bundle event structures is used. For guarded recursive processes, we show the consistency between our non-interleaving semantics and the ET-LOTOS interleaving semantics. Since our semantic model does not have an explicit notion of the passage of time (as opposed to the interleaving semantics), we are able to handle unguarded recursion and Zeno behaviours in a perspicuous way.