Specification and modeling of dynamic, distributed real-time systems

Time constrained systems which operate in dynamic 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. The paper presents a specification language for describing environment dependent features. Also presented is an abstract model that is constructed (statically) from the specifications, and is augmented (dynamically,) with the state of environment dependent features. The model is used to define techniques for QoS (quality of service) monitoring, QoS diagnosis, and resource 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 of distributed computer and network resources.