We introduce BURN, a methodology to create customized benchmarks for testing multitier applications under time-varying resource usage conditions. Starting from a set of preexisting test workloads, BURN finds a policy that interleaves their execution to stress the multitier application and generate controlled burstiness in resource consumption. This is useful to study, in a controlled way, the robustness of software services to sudden changes in the workload characteristics and in the usage levels of the resources. The problem is tackled by a model-based technique which first generates Markov models to describe resource consumption patterns of each test workload. Then, a policy is generated using an optimization program which sets as constraints a target request mix and user-specified levels of burstiness at the different resources in the system. Burstiness is quantified using a novel metric called overdemand, which describes in a natural way the tendency of a workload to keep a resource congested for long periods of time and across multiple requests. A case study based on a three-tier application testbed shows that our method is able to control and predict burstiness for session service demands at a fine-grained scale. Furthermore, experiments demonstrate that for any given request mix our approach can expose latency and throughput degradations not found with nonbursty workloads having the same request mix.

We present a new technique for predicting the resource demand requirements of services implemented by multitier systems. Accurate demand estimates are essential to ensure the efficient provisioning of services in an increasingly service-oriented world. The demand estimation technique proposed in this paper has several advantages compared with regression-based demand estimation techniques, which many practitioners employ today. In contrast to regression, it does not suffer from the problem of multicollinearity, it provides more reliable aggregate resource demand and confidence interval predictions, and it offers a measurement-based validation test. The technique can be used to support system sizing and capacity planning exercises, costing and pricing exercises, and to predict the impact of changes to a service upon different service customers.

With the advent of m-learning, efficient rendition of XML-based assessments such as the QTIv2.1 is increasingly important. However, XML processing requires significant resources on resource-limited mobile devices. This paper presents an approach and architecture that bypass this problem by automatically generating self-contained Flash-Lite assessments from QTIv2.1 packages. A specialized object model of the QTIv2.1 is used in conjunction with open-source tools to generate assessments that are approximately five times smaller than those manually generated using macromedia learning interactions.