The paper “Performability Analysis: A New Algorithm” describes an algorithm for computing the complementary distribution of the accumulated reward over an interval of time in a homogeneous Markov process. In this comment, we show that in two particular cases, one of which is quite frequent, small modifications of the algorithm may reduce significantly its storage complexity.

Web analytics is the measurement, collection, analysis and summarizing of internet data for purposes of understanding and optimizing web usage. To check the web analytics the website IJCT is considered. This paper is the first step to analyze the availability and performability of the site. Availability depicts that for how much time the system is up i.e. check the utilization of the system on ...

We describe a novel model checking algorithm for analysing the behaviour of stochastic systems with respect to their performability. Systems are modelled as actionlabelled CTMCs, and the properties to be veri ed are speci ed with the help of the action-based temporal logic aCSL. The technique is currently being implemented in our freely available prototype tool ETMCC.

Performability modelling has been most successfully applied for gracefully degradable computer systems by using Markov reward models [2]. In this approach the relation of the performability model with the underlying performance and dependability model is exploited. For many systems and for many measures of interest this type of modelling is not suited, so another performability modelling approa...

Abstract Formal methods such as CSP (Communicating Sequential Processes) are widely used for reasoning about concurrency, communication, safety and liveness issues. Some of these models have been extended to permit reasoning about real-time constraints. Yet, the research in formal specification and verification of complex systems has often ignored the specification of stochastic properties of t...

Recently, application of network systems ( e.g. , cloud computing systems) is increasingly prevalent for achieving integration, sharing and efficient utilization various resources. A parallel task in a system has multiple subtasks that can be executed different servers parallel. However, failures any subtask inevitably result the entire cannot complete. To avoid such situation, create some copi...

This paper seeks to identify some of the technology challenges and research opportunities in assessing, optimising and assuring performance and dependability on the grid. Grid computing offers many scientific and commercial benefits, but also many technical and organisational challenges. Amongst the challenges for grid computing is the need to provide reliable quality of service to end users, w...

We construct for the first time a fractional-order hyperchaotic system via original integer-order system. The dynamical behavior of this is investigated in detail using approximation method and Lyapunov exponents. Next, an adaptive control strategy univariate controlled has been proposed. Also, tracking performance fully taken into account numerous applications, instance, sinusoidal periodic si...