Transforming a service-oriented application model to a workload model: Master's thesis

The goal of this master’s thesis was to develop a method for transforming a service-oriented application model to a workload model. The focus was on real-time embedded systems interacting directly with end-users, e.g. terminals. The transformation method is needed in the model based performance validation approach developed at VTT, the Technical Research Centre of Finland. In the approach an application is modelled with a service-oriented modelling method which is then transformed to a workload model. A performance simulation model is then obtained by combining the workload model with an execution platform model. Finally, the simulation model is executed and results are used to validate the performance. By using the workload models the validation can be done already in the early phase of the design process, a step which is necessary to minimise design costs. This work concentrates on the application side of the performance evaluation method especially on transformation method. The platform side of the method is presented in more detail in the master’s thesis of Tuomo Kestilä, which will be published late 2007. In this work the application modelling was done with the LYRA method, which is a service-oriented and application-specific application modelling method. The work describes how a workload model is obtained from a service-oriented application model. The idea of the workload model is to present the load that software causes on a platform when it is executed. The benefit of using workload models is increased simulation speed as the functionality is not simulated and they can be easily modified to quickly evaluate various versions of use cases. The workload has a layered hierarchical structure consisting of four layers: main, application, process, and function layer. The higher layers are built on top of the lower layers. The workload model and the execution platform model are combined by defining the interface between them in the UML model. This requires that the platform skeleton model is included in the UML model. Before the integration of models can be done and a simulation model compiled the workload model must be transformed into SystemC. This is done automatically with the SystemC code generator. The transformation method developed in this thesis is validated by using it in the Virtual Network Computing (VNC) case study. The application model was modelled from the requirement specification, the model was transformed to the workload model by using the transformation method, the workload was transformed into SystemC, and the combination of workload and platform was compiled and executed. Based on the case study the transformation method was discovered to be valid.