Software Performance Engineering (SPE) has a great impact on software life cycle. Introducing the concept of software architecture evaluation in early stages of software development life cycle reduces the cost of rework to a great extent. Performance characteristics like response time, throughput, and the rate of processor or resource utilization play an important role in defining the quality of software. The derivation of performance results of a software product, during the early stages of the software life cycle can be achieved by quantitatively evaluating the software performance model. There has been lot of research identifying the methods of evaluating software.'^ The evaluation process starts by analyzing the performance model which is derived from the software model annotated with suitable usage profiles. This paper provides a simple step-by-step approach of converting the software models represented as UML diagrams using the profile for Schedulability, Performance and Time specifications (SPT) into Layered Queuing Network (LQN) performance models.

Keywords - Usage profiles, Unified modeling language, Performance model, Model Driven Development