SCEst: Sequentially constructive esterel. The synchronous language Esterel provides determinate concurrency for reactive systems. Determinacy is ensured by the “signal coherence rule,” which demands that signals have a stable value throughout one reaction cycle. This is natural for the original application domains of Esterel, such as controller design and hardware development; however, it is unnecessarily restrictive for software development. Sequentially Constructive Esterel (SCEst) overcomes this restriction by allowing values to change instantaneously, as long as determinacy is still guaranteed, adopting the recently proposed Sequentially Constructive model of computation. SCEst is grounded in the minimal Sequentially Constructive Language, which also provides a novel semantic definition and compilation approach for Esterel.