Performance analysis in the early design of software

Introduces a methodology to transform descriptions of systems into models suitable for performance analysis. The need for metrics and measurements of different system qualities throughout the life-cycle of a system, following the ideas in Rapp and Sjodin (1983) is also discussed. Special emphasis is put on the early design phases in the sense that most of the design-decisions are tried out before implementing the system, to ensure anticipated behaviour. The main idea of the modelling methodology is to divide the system into two model types. One model concerns the use processes of the system, which are reflected in user behaviour and application software. The other model concerns the queue structures and architecture of the system. These two models could be combined in different ways resulting in either a so called Queue-Flow Model or a Performance Prototyping Simulator. The maturity of the models will depend on where in the life-cycle they are developed, i.e. how much information and knowledge are available. The methodology suggested is based on CCITT-SDL for the description of the software. One of its major benefits besides from being a standard is its formal representation, which makes modelling and parameter extraction easier