An Extended Weak Isomorphism for Model

This paper will describe an extension to Hillston's original weak isomorphism relation for PEPA. Previously it catered for the reduction of sequences of silent activities performed by a process; the stochastic model used was a GSMP which allowed generally distributed activities. We extend the relation to allow for the reduction of more general structure which need not encompass only silent activities. This impacts the calculation of performance measures and these eeects are studied. The motivation is that consideration of the performance measure in partnership with the process can allow for useful reductions in model complexity.