A Denotational Model for Instantaneous Signal Calculus

In this paper we explore an observation-oriented denotational semantics for instantaneous signal calculus which contains all conceptually instantaneous reactions of signal calculus for event-based synchronous languages. The healthiness conditions are studied for especially dealing with the emission of signals. Every instantaneous reaction can be identified as denoting a healthiness function over the set of events which describe the state of the system and its environment. The normal form, surprisingly, has the comparatively elegant and straightforward denotational semantic definition. Furthermore, a set of algebraic laws concerning the distinct features for instantaneous signal calculus is investigated. All algebraic laws can be established in the framework of our semantic model, i.e., if the equality of two differently written instantaneous reactions is algebraically provable, the two reactions are also equivalent with respect to the denotational semantics.