Software performance engineering [13] (SPE) proposes methods to evaluate performance of software systems early in the development process. A SPE accepted approach consists in deriving performance models from UML specifications, usually annotated according to the OMG Profile for Schedulability, Performance and Time Specification [12] (UML-SPT). Performance models use to be based on simulation environments or a given modelling formalism: (layered) queuing networks, stochastic Petri nets or stochastic process algebras. Some tools are being developed under this SPE approach [9, 4, 6, 5]. OMG has defined a framework for SPE tools, which is a standard for communicating information between tools, see Figure 1.