Specification and Modeling of Dynamic, Distributed Real-Time Systems

This paper presents an approach for engineering time-constrained systems which must operate in dynamic environments. Systems which operate in such environments may have unknown worst-case scenarios, may have large variances in the sizes of the data and event sets that they process (and thus, have large variances in execution latencies and resource requirements), and may not be statically characterizable, even by time-invariant statistical distributions. To enable the engineering of such systems, we have developed a specification language that enables the description of environment-dependent features. We also present an abstract model that is constructed from the specifications, and is augmented dynamically with the state of environment-dependent features. The model is also used to define techniques for QoS (quality-of-service) monitoring, QoS diagnosis, and allocation analysis. Experimental results show the effectiveness of the approach for specification of real-time QoS, detection and diagnosis of QoS failures, and restoration of acceptable QoS via reallocation.