Quasi-synchronism: a Step Away from the Traditional Fault-tolerant Real-time System Models

Distributed fault-tolerant real-time system models have exhibited a trend to polarize themselves in extreme positions. In this paper, we assess the tness of current models to represent the attributes underlying the distributed fault-tolerance of real-time systems. Namely, we are concerned with the correctness issues arising from the temporal properties of interprocess communication: reliable and ordered group communication, replication management protocols, time services, etc. We are particularly concerned with best-eeort or mission-critical systems, where despite the hard need to fulll timing guarantees, this cannot be ensured at all times in a given operational envelope, mandating that the system be highly dynamic and adaptive. In the paper, we suggest quasi-synchronism as a framework to address this kind of systems. We nalize by pointing out some contributions to materialize the model.